Номер 3, страница 137 - гдз по физике 9 класс учебник Изергин

Физика, 9 класс Учебник, автор: Изергин Эдуард Тимофеевич, издательство Русское слово, Москва, 2019

Авторы: Изергин Э. Т.

Тип: Учебник

Серия: инновационная школа

Издательство: Русское слово

Год издания: 2019 - 2026

Цвет обложки: синий

ISBN: 978-5-533-01069-6

Глава IV. Электромагнитные колебания и волны. Параграф 28. Радиоприём - номер 3, страница 137.

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                    "field_for_whom" => "Учебник для 9 класса общеобразовательных организаций"
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                    "field_default_folder" => "/fizika_09/izergin-u/"
                    "field_isbn" => "978-5-533-01069-6"
                    "field_cover" => array:1 [ …1]
                    "field_cover_alts" => array:1 [ …1]
                    "field_covers" => array:1 [ …1]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1092 …2}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1093 …2}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1094 …2}
                    "field_url" => "/9-klass/fizika/izergin-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1095 …2}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "breadcrumbs" => array:3 [ …3]
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                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
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                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1097
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              #escapeWhenCastingToString: false
            }
          ]
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            "id" => 1439571
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Электромагнитные колебания и волны"
            "field_branch_order" => "IV"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1065}
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            0 => "*"
          ]
        }
        1 => App\Models\Branch {#1098
          #connection: "mysql"
          #table: "branches"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
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          #attributes: array:24 [
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            "created_at" => "2026-04-10 13:58:26"
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                0 => App\Models\Term {#1100
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
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                  #attributes: array:7 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
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                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
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                  #attributeCastCache: []
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
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            "book" => Illuminate\Database\Eloquent\Collection {#1101
              #items: array:1 [
                0 => App\Models\Book {#1102
                  #connection: "mysql"
                  #table: "books"
                  #primaryKey: "id"
                  #keyType: "int"
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                  #attributes: array:50 [
                    "id" => 4169
                    "created_at" => "2026-04-10 13:58:26"
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                    "field_country" => Illuminate\Database\Eloquent\Collection {#1114 …2}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1116 …2}
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                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1122 …2}
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                0 => App\Models\Branch {#1132
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        }
      ]
      #escapeWhenCastingToString: false
    }
    "content" => Illuminate\Database\Eloquent\Collection {#1137
      #items: array:2 [
        0 => App\Models\Element {#1138
          #connection: "mysql"
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              #items: array:1 [
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                  #connection: "mysql"
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                    "created_at" => "2026-04-10 13:58:26"
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                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1141 …2}
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            "text" => "<p><strong>3.</strong> Какие функции выполняют антенна и заземление, колебательный контур с конденсатором переменной ёмкости, детектор, конденсатор постоянной ёмкости, телефон?</p>"
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                "width" => "1446"
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            "edition" => Illuminate\Database\Eloquent\Collection {#1139}
            "task" => array:2 [
              "refs" => "1439841"
              "type" => "task"
            ]
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            "text" => "<p><strong>Антенна и заземление</strong></p><p>Антенна улавливает электромагнитные волны, излучаемые радиостанциями. Под действием переменного электромагнитного поля волны в антенне возникают вынужденные электромагнитные колебания очень малой амплитуды — слабый переменный ток высокой частоты. Заземление создаёт второй полюс для подключения колебательного контура, образуя вместе с антенной цепь, в которой наводятся токи от приходящих радиоволн. Таким образом, антенна и заземление являются входным устройством, преобразующим энергию радиоволны в энергию электрического сигнала.</p><p><strong>Ответ:</strong> Антенна и заземление служат для приёма электромагнитных волн и преобразования их энергии в энергию электрических колебаний.</p><p><strong>Колебательный контур с конденсатором переменной ёмкости</strong></p><p>Колебательный контур, состоящий из катушки индуктивности ($\text{L}$) и конденсатора переменной ёмкости ($\text{C}$), выполняет функцию селекции (выбора) нужной радиостанции. Каждая станция вещает на своей определённой частоте. Изменяя ёмкость конденсатора, мы меняем собственную частоту колебаний контура, которая определяется по формуле Томсона: $f_0 = \frac{1}{2\pi\sqrt{LC}}$. Когда собственная частота контура $f_0$ совпадает с частотой несущей волны принимаемой радиостанции, наступает явление резонанса. При этом амплитуда колебаний в контуре для данной частоты резко возрастает, в то время как сигналы других радиостанций, работающих на других частотах, остаются слабыми и практически не влияют на приём.</p><p><strong>Ответ:</strong> Колебательный контур с конденсатором переменной ёмкости выполняет функцию выделения сигнала нужной радиостанции из множества сигналов, принятых антенной, путём настройки в резонанс.</p><p><strong>Детектор</strong></p><p>После колебательного контура сигнал представляет собой высокочастотные колебания, модулированные по амплитуде низкочастотным (звуковым) сигналом. Функция детектора — выделить из этого модулированного сигнала низкочастотную составляющую. Этот процесс называется детектированием или демодуляцией. В простейших приёмниках в качестве детектора используется полупроводниковый диод, который обладает односторонней проводимостью. Он пропускает ток только в одном направлении, «срезая» одну половину высокочастотных колебаний. В результате получается пульсирующий ток, огибающая которого повторяет форму полезного звукового сигнала.</p><p><strong>Ответ:</strong> Детектор служит для выделения низкочастотного (звукового) сигнала из принятого модулированного высокочастотного сигнала.</p><p><strong>Конденсатор постоянной ёмкости</strong></p><p>Этот конденсатор, также называемый блокировочным или сглаживающим, подключается параллельно телефону (наушникам) после детектора. Его задача — отфильтровать оставшуюся высокочастотную составляющую (пульсации) из сигнала. Конденсатор имеет малое сопротивление для токов высокой частоты и большое — для токов низкой частоты. Поэтому высокочастотные пульсации проходят через конденсатор, минуя телефон, а низкочастотный (звуковой) сигнал идёт на телефон. Это делает звук на выходе более чистым и громким.</p><p><strong>Ответ:</strong> Конденсатор постоянной ёмкости сглаживает пульсации тока после детектора, отфильтровывая остатки высокочастотной несущей частоты и пропуская на телефон только низкочастотный звуковой сигнал.</p><p><strong>Телефон</strong></p><p>Телефон (или головные телефоны/наушники) является оконечным устройством радиоприёмника. Его функция — преобразовать отфильтрованный низкочастотный электрический сигнал обратно в звуковые волны. Проходя через катушку электромагнита телефона, низкочастотный ток создаёт переменное магнитное поле, которое заставляет колебаться металлическую мембрану с той же частотой. Колебания мембраны создают в воздухе звуковые волны, которые и воспринимаются слушателем как звук (речь, музыка).</p><p><strong>Ответ:</strong> Телефон преобразует низкочастотные электрические колебания (звуковой сигнал) в слышимые звуковые колебания.</p>"
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            "task" => array:2 [
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            "text" => "<p><strong>Антенна и заземление</strong></p><p>Антенна улавливает электромагнитные волны, излучаемые радиостанциями. Под действием переменного электромагнитного поля волны в антенне возникают вынужденные электромагнитные колебания очень малой амплитуды — слабый переменный ток высокой частоты. Заземление создаёт второй полюс для подключения колебательного контура, образуя вместе с антенной цепь, в которой наводятся токи от приходящих радиоволн. Таким образом, антенна и заземление являются входным устройством, преобразующим энергию радиоволны в энергию электрического сигнала.</p><p><strong>Ответ:</strong> Антенна и заземление служат для приёма электромагнитных волн и преобразования их энергии в энергию электрических колебаний.</p><p><strong>Колебательный контур с конденсатором переменной ёмкости</strong></p><p>Колебательный контур, состоящий из катушки индуктивности ($\text{L}$) и конденсатора переменной ёмкости ($\text{C}$), выполняет функцию селекции (выбора) нужной радиостанции. Каждая станция вещает на своей определённой частоте. Изменяя ёмкость конденсатора, мы меняем собственную частоту колебаний контура, которая определяется по формуле Томсона: $f_0 = \frac{1}{2\pi\sqrt{LC}}$. Когда собственная частота контура $f_0$ совпадает с частотой несущей волны принимаемой радиостанции, наступает явление резонанса. При этом амплитуда колебаний в контуре для данной частоты резко возрастает, в то время как сигналы других радиостанций, работающих на других частотах, остаются слабыми и практически не влияют на приём.</p><p><strong>Ответ:</strong> Колебательный контур с конденсатором переменной ёмкости выполняет функцию выделения сигнала нужной радиостанции из множества сигналов, принятых антенной, путём настройки в резонанс.</p><p><strong>Детектор</strong></p><p>После колебательного контура сигнал представляет собой высокочастотные колебания, модулированные по амплитуде низкочастотным (звуковым) сигналом. Функция детектора — выделить из этого модулированного сигнала низкочастотную составляющую. Этот процесс называется детектированием или демодуляцией. В простейших приёмниках в качестве детектора используется полупроводниковый диод, который обладает односторонней проводимостью. Он пропускает ток только в одном направлении, «срезая» одну половину высокочастотных колебаний. В результате получается пульсирующий ток, огибающая которого повторяет форму полезного звукового сигнала.</p><p><strong>Ответ:</strong> Детектор служит для выделения низкочастотного (звукового) сигнала из принятого модулированного высокочастотного сигнала.</p><p><strong>Конденсатор постоянной ёмкости</strong></p><p>Этот конденсатор, также называемый блокировочным или сглаживающим, подключается параллельно телефону (наушникам) после детектора. Его задача — отфильтровать оставшуюся высокочастотную составляющую (пульсации) из сигнала. Конденсатор имеет малое сопротивление для токов высокой частоты и большое — для токов низкой частоты. Поэтому высокочастотные пульсации проходят через конденсатор, минуя телефон, а низкочастотный (звуковой) сигнал идёт на телефон. Это делает звук на выходе более чистым и громким.</p><p><strong>Ответ:</strong> Конденсатор постоянной ёмкости сглаживает пульсации тока после детектора, отфильтровывая остатки высокочастотной несущей частоты и пропуская на телефон только низкочастотный звуковой сигнал.</p><p><strong>Телефон</strong></p><p>Телефон (или головные телефоны/наушники) является оконечным устройством радиоприёмника. Его функция — преобразовать отфильтрованный низкочастотный электрический сигнал обратно в звуковые волны. Проходя через катушку электромагнита телефона, низкочастотный ток создаёт переменное магнитное поле, которое заставляет колебаться металлическую мембрану с той же частотой. Колебания мембраны создают в воздухе звуковые волны, которые и воспринимаются слушателем как звук (речь, музыка).</p><p><strong>Ответ:</strong> Телефон преобразует низкочастотные электрические колебания (звуковой сигнал) в слышимые звуковые колебания.</p>"
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                    "field_patronymic" => "Тимофеевич"
                    "field_surname_rp" => null
                  ]
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                  #attributeCastCache: []
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                  #visible: []
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                    0 => "*"
                  ]
                }
              ]
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            }
            "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1164
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              #escapeWhenCastingToString: false
            }
            "field_book_type" => Illuminate\Database\Eloquent\Collection {#1165
              #items: array:1 [
                0 => App\Models\Term {#1166
                  #connection: "mysql"
                  #table: "terms"
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                  #keyType: "int"
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                  #attributes: array:10 [
                    "id" => 6671
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
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                    "field_book_type_foreign" => null
                    "field_cases" => array:6 [ …6]
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                  ]
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_country" => Illuminate\Database\Eloquent\Collection {#1167
              #items: array:1 [
                0 => App\Models\Term {#1168
                  #connection: "mysql"
                  #table: "terms"
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                  #keyType: "int"
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                  #attributes: array:6 [
                    "id" => 9
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Россия"
                    "field_cases" => array:6 [ …6]
                    "field_translit" => "rossiya"
                  ]
                  #original: array:6 [
                    "id" => 9
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Россия"
                    "field_cases" => array:6 [ …6]
                    "field_translit" => "rossiya"
                  ]
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                    0 => "*"
                  ]
                }
              ]
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            }
            "field_city" => Illuminate\Database\Eloquent\Collection {#1169
              #items: array:1 [
                0 => App\Models\Term {#1170
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
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                  #withCount: []
                  +preventsLazyLoading: false
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                  #escapeWhenCastingToString: false
                  #attributes: array:6 [
                    "id" => 15
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Москва"
                    "field_cases" => array:6 [ …6]
                    "field_translit" => "moskva"
                  ]
                  #original: array:6 [
                    "id" => 15
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Москва"
                    "field_cases" => array:6 [ …6]
                    "field_translit" => "moskva"
                  ]
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                  #attributeCastCache: []
                  #dateFormat: null
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                  #visible: []
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_series" => Illuminate\Database\Eloquent\Collection {#1171
              #items: array:1 [
                0 => App\Models\Term {#1172
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
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                  #escapeWhenCastingToString: false
                  #attributes: array:8 [
                    "id" => 4715
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "инновационная школа"
                    "field_cases" => null
                    "field_foreign_lang_series" => null
                    "field_transcription_eng" => null
                    "field_translit" => "innovacionnaya shkola"
                  ]
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                    "id" => 4715
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                    "updated_at" => null
                    "name" => "инновационная школа"
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                    "field_translit" => "innovacionnaya shkola"
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                    0 => "*"
                  ]
                }
              ]
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            }
            "field_umk" => Illuminate\Database\Eloquent\Collection {#1173
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1174
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1175
              #items: array:1 [
                0 => App\Models\Term {#1176
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
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                  #attributes: array:10 [
                    "id" => 6706
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "ФГОС (старый)"
                    "field_cases" => array:6 [ …6]
                    "field_color" => null
                    "field_end_year" => "2022"
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                    "field_translit" => "fgos-old"
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                  ]
                  #original: array:10 [
                    "id" => 6706
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "ФГОС (старый)"
                    "field_cases" => array:6 [ …6]
                    "field_color" => null
                    "field_end_year" => "2022"
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                  ]
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_publication_number" => null
            "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1177
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              #escapeWhenCastingToString: false
            }
            "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1178
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_under_the_edition_degree" => null
            "field_cover_description" => null
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            "field_part" => ""
            "field_part_writing" => ""
            "field_second_foreign_language" => null
            "field_for_whom" => "Учебник для 9 класса общеобразовательных организаций"
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            "field_link_to_source" => null
            "field_tasks_count" => "388"
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            "field_default_folder" => "/fizika_09/izergin-u/"
            "field_isbn" => "978-5-533-01069-6"
            "field_cover" => array:1 [
              0 => "/media/fizika_09/izergin-u/covers/cover1.webp?ts=1759162386"
            ]
            "field_cover_alts" => array:1 [
              0 => ""
            ]
            "field_covers" => array:1 [
              0 => array:4 [
                "path" => "/media/fizika_09/izergin-u/covers/cover1.webp?ts=1759162386"
                "alt" => ""
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              ]
            ]
            "field_popular_book" => "0"
            "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1179
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_new_book" => Illuminate\Database\Eloquent\Collection {#1180
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_old_book" => Illuminate\Database\Eloquent\Collection {#1181
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_url" => "/9-klass/fizika/izergin-uchebnik"
            "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1182
              #items: array:1 [
                0 => App\Models\Term {#1183
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
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                  #escapeWhenCastingToString: false
                  #attributes: array:6 [
                    "id" => 49
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "синий"
                    "field_cases" => array:6 [ …6]
                    "field_translit" => "siniy"
                  ]
                  #original: array:6 [
                    "id" => 49
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "синий"
                    "field_cases" => array:6 [ …6]
                    "field_translit" => "siniy"
                  ]
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                    0 => "*"
                  ]
                }
              ]
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            }
            "field_metatags_title" => null
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            "breadcrumbs" => array:3 [
              "class" => 380
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              "class_subject" => 493
            ]
          ]
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            "id" => 4169
            "created_at" => "2026-04-10 13:58:26"
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            "field_tree_default_status" => "tasks"
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            "field_subject" => Illuminate\Database\Eloquent\Collection {#1156}
            "field_class" => Illuminate\Database\Eloquent\Collection {#1158}
            "field_publisher" => Illuminate\Database\Eloquent\Collection {#1160}
            "field_author" => Illuminate\Database\Eloquent\Collection {#1162}
            "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1164}
            "field_book_type" => Illuminate\Database\Eloquent\Collection {#1165}
            "field_country" => Illuminate\Database\Eloquent\Collection {#1167}
            "field_city" => Illuminate\Database\Eloquent\Collection {#1169}
            "field_series" => Illuminate\Database\Eloquent\Collection {#1171}
            "field_umk" => Illuminate\Database\Eloquent\Collection {#1173}
            "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1174}
            "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1175}
            "field_publication_number" => null
            "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1177}
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            "field_under_the_edition_degree" => null
            "field_cover_description" => null
            "field_publication_year" => "2019"
            "field_publication_year_until" => null
            "field_part" => ""
            "field_part_writing" => ""
            "field_second_foreign_language" => null
            "field_for_whom" => "Учебник для 9 класса общеобразовательных организаций"
            "field_allowed" => null
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            "field_link_to_source" => null
            "field_tasks_count" => "388"
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            "field_default_folder" => "/fizika_09/izergin-u/"
            "field_isbn" => "978-5-533-01069-6"
            "field_cover" => array:1 [
              0 => "/media/fizika_09/izergin-u/covers/cover1.webp?ts=1759162386"
            ]
            "field_cover_alts" => array:1 [
              0 => ""
            ]
            "field_covers" => array:1 [
              0 => array:4 [
                "path" => "/media/fizika_09/izergin-u/covers/cover1.webp?ts=1759162386"
                "alt" => ""
                "width" => "1881"
                "height" => "2502"
              ]
            ]
            "field_popular_book" => "0"
            "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1179}
            "field_new_book" => Illuminate\Database\Eloquent\Collection {#1180}
            "field_old_book" => Illuminate\Database\Eloquent\Collection {#1181}
            "field_url" => "/9-klass/fizika/izergin-uchebnik"
            "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1182}
            "field_metatags_title" => null
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            "breadcrumbs" => array:3 [
              "class" => 380
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              "class_subject" => 493
            ]
          ]
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          +timestamps: true
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          #guarded: array:1 [
            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "page" => Illuminate\Database\Eloquent\Collection {#1729
      #items: array:1 [
        0 => App\Models\BookPage {#1188
          #connection: "mysql"
          #table: "book_pages"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
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          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:21 [
            "id" => 1439455
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_page_start" => "137"
            "field_url" => "/9-klass/fizika/izergin-uchebnik/page-137"
            "field_display_title" => "137"
            "field_folder" => "1"
            "field_image_name" => "137"
            "field_branch_parent" => Illuminate\Database\Eloquent\Collection {#1191
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_weight" => "0"
            "field_book_parent" => Illuminate\Database\Eloquent\Collection {#1190
              #items: array:1 [
                0 => App\Models\Book {#1192
                  #connection: "mysql"
                  #table: "books"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
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                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:50 [
                    "id" => 4169
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_tree_default_status" => "tasks"
                    "field_pages_status" => null
                    "field_subject" => Illuminate\Database\Eloquent\Collection {#1193 …2}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1195 …2}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1197 …2}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1199 …2}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1201 …2}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1202 …2}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1204 …2}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1206 …2}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1208 …2}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1210 …2}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1211 …2}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1212 …2}
                    "field_publication_number" => null
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1214 …2}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1215 …2}
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => null
                    "field_publication_year" => "2019"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебник для 9 класса общеобразовательных организаций"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "388"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_09/izergin-u/"
                    "field_isbn" => "978-5-533-01069-6"
                    "field_cover" => array:1 [ …1]
                    "field_cover_alts" => array:1 [ …1]
                    "field_covers" => array:1 [ …1]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1216 …2}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1217 …2}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1218 …2}
                    "field_url" => "/9-klass/fizika/izergin-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1219 …2}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
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                    "field_description_top" => null
                    "field_description_bottom" => null
                    "breadcrumbs" => array:3 [ …3]
                  ]
                  #original: array:50 [
                    "id" => 4169
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_tree_default_status" => "tasks"
                    "field_pages_status" => null
                    "field_subject" => Illuminate\Database\Eloquent\Collection {#1193 …2}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1195 …2}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1197 …2}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1199 …2}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1201 …2}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1202 …2}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1204 …2}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1206 …2}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1208 …2}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1210 …2}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1211 …2}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1212 …2}
                    "field_publication_number" => null
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1214 …2}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1215 …2}
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => null
                    "field_publication_year" => "2019"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебник для 9 класса общеобразовательных организаций"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "388"
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№3 (с. 137)
Условие. №3 (с. 137)
скриншот условия
Физика, 9 класс Учебник, автор: Изергин Эдуард Тимофеевич, издательство Русское слово, Москва, 2019, страница 137, номер 3, Условие

3. Какие функции выполняют антенна и заземление, колебательный контур с конденсатором переменной ёмкости, детектор, конденсатор постоянной ёмкости, телефон?

Решение. №3 (с. 137)

Антенна и заземление

Антенна улавливает электромагнитные волны, излучаемые радиостанциями. Под действием переменного электромагнитного поля волны в антенне возникают вынужденные электромагнитные колебания очень малой амплитуды — слабый переменный ток высокой частоты. Заземление создаёт второй полюс для подключения колебательного контура, образуя вместе с антенной цепь, в которой наводятся токи от приходящих радиоволн. Таким образом, антенна и заземление являются входным устройством, преобразующим энергию радиоволны в энергию электрического сигнала.

Ответ: Антенна и заземление служат для приёма электромагнитных волн и преобразования их энергии в энергию электрических колебаний.

Колебательный контур с конденсатором переменной ёмкости

Колебательный контур, состоящий из катушки индуктивности ($\text{L}$) и конденсатора переменной ёмкости ($\text{C}$), выполняет функцию селекции (выбора) нужной радиостанции. Каждая станция вещает на своей определённой частоте. Изменяя ёмкость конденсатора, мы меняем собственную частоту колебаний контура, которая определяется по формуле Томсона: $f_0 = \frac{1}{2\pi\sqrt{LC}}$. Когда собственная частота контура $f_0$ совпадает с частотой несущей волны принимаемой радиостанции, наступает явление резонанса. При этом амплитуда колебаний в контуре для данной частоты резко возрастает, в то время как сигналы других радиостанций, работающих на других частотах, остаются слабыми и практически не влияют на приём.

Ответ: Колебательный контур с конденсатором переменной ёмкости выполняет функцию выделения сигнала нужной радиостанции из множества сигналов, принятых антенной, путём настройки в резонанс.

Детектор

После колебательного контура сигнал представляет собой высокочастотные колебания, модулированные по амплитуде низкочастотным (звуковым) сигналом. Функция детектора — выделить из этого модулированного сигнала низкочастотную составляющую. Этот процесс называется детектированием или демодуляцией. В простейших приёмниках в качестве детектора используется полупроводниковый диод, который обладает односторонней проводимостью. Он пропускает ток только в одном направлении, «срезая» одну половину высокочастотных колебаний. В результате получается пульсирующий ток, огибающая которого повторяет форму полезного звукового сигнала.

Ответ: Детектор служит для выделения низкочастотного (звукового) сигнала из принятого модулированного высокочастотного сигнала.

Конденсатор постоянной ёмкости

Этот конденсатор, также называемый блокировочным или сглаживающим, подключается параллельно телефону (наушникам) после детектора. Его задача — отфильтровать оставшуюся высокочастотную составляющую (пульсации) из сигнала. Конденсатор имеет малое сопротивление для токов высокой частоты и большое — для токов низкой частоты. Поэтому высокочастотные пульсации проходят через конденсатор, минуя телефон, а низкочастотный (звуковой) сигнал идёт на телефон. Это делает звук на выходе более чистым и громким.

Ответ: Конденсатор постоянной ёмкости сглаживает пульсации тока после детектора, отфильтровывая остатки высокочастотной несущей частоты и пропуская на телефон только низкочастотный звуковой сигнал.

Телефон

Телефон (или головные телефоны/наушники) является оконечным устройством радиоприёмника. Его функция — преобразовать отфильтрованный низкочастотный электрический сигнал обратно в звуковые волны. Проходя через катушку электромагнита телефона, низкочастотный ток создаёт переменное магнитное поле, которое заставляет колебаться металлическую мембрану с той же частотой. Колебания мембраны создают в воздухе звуковые волны, которые и воспринимаются слушателем как звук (речь, музыка).

Ответ: Телефон преобразует низкочастотные электрические колебания (звуковой сигнал) в слышимые звуковые колебания.

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