thập đại cao thủ live 4h30 sáng số 07 dãn dòng

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<b>THẬP ĐẠI CAO THỦ ‒ LIVE 4H30 SÁNGSỐ 07</b>

<b>Câu 1: [VNA]</b> Cho mạch điện kín gồm một nguồn

<i>điện khơng đổi có suất điện động 12 V , điện trở trong </i>

sự phụ thuộc của hiệu điện thế giữa hai điện cực vào biến trở như hình bên. Điện trở trong của nguồn có giá trị bằng

<b>Câu 2: [VNA]</b> Hạt nhân <i><small>21084</small></i>

<i>γ có giá trị gần đúng là</i>

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<i>0 </i>

<i>R (Ω) U (V) </i>

<i>2 4 6 8 10 12 </i>

<i>10 </i>

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<b>Câu 3: [VNA]</b> Các mức năng lượng của các trạng thái dừng của nguyên tử hidro được xác định

<i>lượng 2,55 eV thì tần số lớn nhất của bức xạ mà nguyên tử hiđro có thể phát ra là</i>

<b> A.</b> <i>3,079.10 Hz¹⁵</i> <b>B.</b> <i>2,057.10 Hz¹⁵</i> <b>C.</b> <i>4,022.10 Hz¹⁵</i> <b>D.</b> <i>3,513 10 Hz</i> <i>¹⁵</i>

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<b>Câu 4: [VNA]</b> Xét một mạch điện gồm một động cơ điện ghép nối tiếp với một tụ điện. Đặt vào hai

<i>đầu mạch một điện áp xoay chiều có giá trị hiệu dụng bằng 100 V thì mạch có hệ số cơng suất là </i>

<i>0,9. Lúc này động cơ hoạt động bình thường với hiệu suất 80% và hệ số công suất 0,75. Biết cường </i>

động có có giá trị bằng

<b> A.</b> <i>6 Ω</i> <b>B.</b> <i>8 Ω</i> <b>C.</b> <i>10 Ω</i> <b>D.</b> <i>12 Ω </i>

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<b>Câu 5: [VNA]</b> Con lắc lò xo dao động điều hòa theo thẳng đứng. Sự phụ thuộc của lực đàn hồi và lực kéo

<b>Câu 6: [VNA]</b> Trong thí nghiệm Y-âng về giao thoa ánh sáng, khi nguồn sáng phát ra ánh sáng

<i>thoa. Biết tổng số vân sáng trên đoạn MN trước và sau khi thay ánh sáng đơn sắc là 25 vân. Số </i>

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<i>A B </i>

<i>O </i>

<i>P Q </i>

<i>v (m/s) F_đh; F_kv (N) </i>

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<b>Câu 7: [VNA]</b> Đặt một hiệu điện thế xoay chiều <i>u U cos ωt φ</i>= <i><small>0</small></i>

(

+

) ( )

<i>V</i> (<i>U và ₀ω</i> không đổi) vào

<i>đoạn mạch AB gồm ba đoạn mạch AM , MN và NB ghép nối tiếp. Đoạn mạch AM chứa điện trở </i>

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<b>Câu 8:[VNA] </b>Thí nghiệm Y-âng về giao thoa ánh sáng, hai khe cách nhau 1 mm, mặt phẳng chứa hai khe cách màn 1,2 m. Ánh sáng đơn sắc trong thí nghiệm có bước sóng 0,48 μm. M và N là hai điểm trên màn, thuộc vùng giao thoa, cách vân sáng trung tâm lần lượt là 10,5 mm và 7,5 mm. Lúc t = 0 bắt đầu cho màn dịch chuyển thẳng đều theo phương vng góc với mặt phẳng chứa hai khe,

trị

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<b>Câu 9:[VNA] </b>Trên mặt nước, tại hai điểm S<small>1</small> và S<small>2</small> cách nhau 21 cm hai nguồn kết hợp dao động

ngắn nhất bằng

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<b>Câu 10:[VNA] </b><i>Một con lắc lị xo gồm vật có khối lượng 100 g là xo nhẹ, độ cứng 20 N/m được treo </i>

thẳng đứng vào một giá cố định, cách sàn đủ cao. Vật được đặt trên giá đỡ nằm ngang sao cho lị

thì khoảng cách giữa vật và giá đỡ là

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