{"segment":[{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"Hai \u0111o\u1ea1n d\u00e2y b\u1eb1ng \u0111\u1ed3ng, c\u00f9ng chi\u1ec1u d\u00e0i, c\u00f3 ti\u1ebft di\u1ec7n v\u00e0 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 $S_{1}^{{}}$, $R_{1}^{{}}$v\u00e0 $S_{2}^{{}}$, $R_{2}^{{}}$. H\u1ec7 th\u1ee9c n\u00e0o d\u01b0\u1edbi \u0111\u00e2y l\u00e0 \u0111\u00fang?","select":["A. $S_{1}^{{}}R_{1}^{{}}=S_{2}^{{}}R_{2}^{{}}$","B. $\\dfrac{S_{1}^{{}}}{R_{1}^{{}}}=\\dfrac{S_{2}^{{}}}{R_{2}^{{}}}$","C. $R_{1}^{{}}R_{2}^{{}}=S_{1}^{{}}S_{2}^{{}}$","D. C\u1ea3 ba h\u1ec7 th\u1ee9c tr\u00ean \u0111\u1ec1u sai."],"hint":"","explain":"<span class='basic_left'>V\u00ec \u0111i\u1ec7n tr\u1edf d\u00e2y d\u1eabn t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi ti\u1ebft di\u1ec7n d\u00e2y d\u1eabn.<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A.<\/span><\/span> ","column":2}]}],"id_ques":2791},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"Hai d\u00e2y d\u1eabn b\u1eb1ng nh\u00f4m c\u00f3 chi\u1ec1u d\u00e0i, ti\u1ebft di\u1ec7n v\u00e0 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 $l_{1}^{{}}$, $S_{1}^{{}}$, $R_{1}^{{}}$ v\u00e0 $l_{2}^{{}}$, $S_{2}^{{}}$, $R_{2}^{{}}$. Bi\u1ebft $l_{1}^{{}}=4l_{2}^{{}}$v\u00e0 $S_{1}^{{}}=2S_{2}^{{}}$. L\u1eadp lu\u1eadn n\u00e0o sau \u0111\u00e2y v\u1ec1 m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c \u0111i\u1ec7n tr\u1edf $R_{1}^{{}}$v\u00e0 $R_{2}^{{}}$ c\u1ee7a hai d\u00e2y d\u1eabn n\u00e0y l\u00e0 \u0111\u00fang?","select":["A. Chi\u1ec1u d\u00e0i l\u1edbn g\u1ea5p 4, ti\u1ebft di\u1ec7n l\u1edbn g\u1ea5p 2 th\u00ec \u0111i\u1ec7n tr\u1edf l\u1edbn g\u1ea5p $4\\times 2=8$ l\u1ea7n, v\u1eady $R_{1}^{{}}=8R_{2}^{{}}$.","B. Chi\u1ec1u d\u00e0i l\u1edbn g\u1ea5p 4 th\u00ec \u0111i\u1ec7n tr\u1edf nh\u1ecf h\u01a1n 4 l\u1ea7n, ti\u1ebft di\u1ec7n l\u1edbn g\u1ea5p 2 th\u00ec \u0111i\u1ec7n tr\u1edf l\u1edbn g\u1ea5p 2 l\u1ea7n, v\u1eady $R_{1}^{{}}=\\dfrac{R_{2}^{{}}}{2}$.","C. Chi\u1ec1u d\u00e0i l\u1edbn g\u1ea5p 4 th\u00ec \u0111i\u1ec7n tr\u1edf l\u1edbn g\u1ea5p 4 l\u1ea7n, ti\u1ebft di\u1ec7n l\u1edbn g\u1ea5p 2 th\u00ec \u0111i\u1ec7n tr\u1edf nh\u1ecf h\u01a1n 2 l\u1ea7n, v\u1eady $R_{1}^{{}}=2R_{2}^{{}}$.","D. Chi\u1ec1u d\u00e0i l\u1edbn g\u1ea5p 4, ti\u1ebft di\u1ec7n l\u1edbn g\u1ea5p 2 th\u00ec \u0111i\u1ec7n tr\u1edf nh\u1ecf h\u01a1n $4\\times 2=8$ l\u1ea7n, v\u1eady $R_{1}^{{}}=\\dfrac{R_{2}^{{}}}{8}$."],"hint":"","explain":"<span class='basic_left'>V\u00ec \u0111i\u1ec7n tr\u1edf t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi chi\u1ec1u d\u00e0i, v\u1edbi \u0111i\u1ec7n tr\u1edf su\u1ea5t v\u00e0 t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y. <br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":1}]}],"id_ques":2792},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"\u0110\u1ec3 t\u00ecm hi\u1ec3u s\u1ef1 ph\u1ee5 thu\u1ed9c c\u1ee7a \u0111i\u1ec7n tr\u1edf d\u00e2y d\u1eabn v\u00e0o ti\u1ebft di\u1ec7n d\u00e2y d\u1eabn, c\u1ea7n ph\u1ea3i x\u00e1c \u0111\u1ecbnh v\u00e0 so s\u00e1nh \u0111i\u1ec7n tr\u1edf c\u1ee7a c\u00e1c d\u00e2y d\u1eabn c\u00f3 nh\u1eefng \u0111\u1eb7c \u0111i\u1ec3m n\u00e0o?","select":["A. C\u00e1c d\u00e2y d\u1eabn n\u00e0y ph\u1ea3i c\u00f3 c\u00f9ng ti\u1ebft di\u1ec7n, \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t v\u1eadt li\u1ec7u, nh\u01b0ng c\u00f3 chi\u1ec1u d\u00e0i kh\u00e1c nhau.","B. C\u00e1c d\u00e2y d\u1eabn n\u00e0y ph\u1ea3i c\u00f3 c\u00f9ng chi\u1ec1u d\u00e0i, \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t v\u1eadt li\u1ec7u, nh\u01b0ng c\u00f3 ti\u1ebft di\u1ec7n kh\u00e1c nhau.","C. C\u00e1c d\u00e2y d\u1eabn n\u00e0y ph\u1ea3i c\u00f3 c\u00f9ng chi\u1ec1u d\u00e0i, c\u00f9ng ti\u1ebft di\u1ec7n, nh\u01b0ng \u0111\u01b0\u1ee3c l\u00e0m b\u1eb1ng c\u00e1c v\u1eadt li\u1ec7u kh\u00e1c nhau.","D. C\u00e1c d\u00e2y d\u1eabn n\u00e0y ph\u1ea3i \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t v\u1eadt li\u1ec7u, nh\u01b0ng c\u00f3 chi\u1ec1u d\u00e0i v\u00e0 ti\u1ebft di\u1ec7n kh\u00e1c nhau."],"hint":"","explain":"<span class='basic_left'>\u0110\u1ec3 t\u00ecm hi\u1ec3u s\u1ef1 ph\u1ee5 thu\u1ed9c c\u1ee7a \u0111i\u1ec7n tr\u1edf d\u00e2y d\u1eabn v\u00e0o ti\u1ebft di\u1ec7n d\u00e2y d\u1eabn, c\u1ea7n ph\u1ea3i x\u00e1c \u0111\u1ecbnh v\u00e0 so s\u00e1nh \u0111i\u1ec7n tr\u1edf c\u1ee7a c\u00e1c d\u00e2y d\u1eabn c\u00f3 c\u00f9ng chi\u1ec1u d\u00e0i, \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t v\u1eadt li\u1ec7u, nh\u01b0ng c\u00f3 ti\u1ebft di\u1ec7n kh\u00e1c nhau.<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":1}]}],"id_ques":2793},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"M\u1ed9t d\u00e2y d\u1eabn \u0111\u1ed3ng ch\u1ea5t c\u00f3 chi\u1ec1u d\u00e0i l, ti\u1ebft di\u1ec7n \u0111\u1ec1u S c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 8\u2126 \u0111\u01b0\u1ee3c g\u1eadp \u0111\u00f4i th\u00e0nh m\u1ed9t d\u00e2y d\u1eabn m\u1edbi c\u00f3 chi\u1ec1u d\u00e0i $\\dfrac{l}{2}$. \u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn m\u1edbi n\u00e0y l\u00e0 bao nhi\u00eau?","select":["A. 4\u2126","B. 6\u2126","C. 8\u2126","D. 2\u2126"],"hint":"","explain":"<span class='basic_left'>Do g\u1eadp \u0111\u00f4i l\u1ea1i n\u00ean chi\u1ec1u d\u00e0i gi\u1ea3m \u0111i 2 l\u1ea7n v\u00e0 ti\u1ebft di\u1ec7n t\u0103ng g\u1ea5p 2 l\u1ea7n. Chi\u1ec1u d\u00e0i gi\u1ea3m 2 l\u1ea7n n\u00ean \u0111i\u1ec7n tr\u1edf gi\u1ea3m hai l\u1ea7n, ti\u1ebft di\u1ec7n t\u0103ng 2 l\u1ea7n n\u00ean \u0111i\u1ec7n tr\u1edf gi\u1ea3m th\u00eam 2 l\u1ea7n k\u1ebft qu\u1ea3 gi\u1ea3m 4 l\u1ea7n. V\u00ec v\u1eady \u0111i\u1ec7n tr\u1edf d\u00e2y d\u1eabn m\u1edbi l\u00e0 $\\dfrac{8}{4}=2\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":2}]}],"id_ques":2794},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":" Hai d\u00e2y d\u1eabn b\u1eb1ng \u0111\u1ed3ng c\u00f3 c\u00f9ng chi\u1ec1u d\u00e0i. D\u00e2y th\u1ee9 nh\u1ea5t c\u00f3 ti\u1ebft di\u1ec7n $S_{1}^{{}}=5m{{m}^{2}}$v\u00e0 \u0111i\u1ec7n tr\u1edf $R_{1}^{{}}=8,5\\Omega $. D\u00e2y th\u1ee9 hai c\u00f3 ti\u1ebft di\u1ec7n $S_{2}^{{}}=0,5m{{m}^{2}}$. T\u00ednh \u0111i\u1ec7n tr\u1edf $R_{2}^{{}}$.","select":["A. 8,5\u2126","B. 85\u2126","C. 50\u2126","D. 55\u2126"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf c\u1ee7a $R_{2}^{{}}$: $R_{2}^{{}}=\\dfrac{R_{1}^{{}}\\times S_{1}^{{}}}{S_{2}^{{}}}=\\dfrac{8,5\\times 5}{0,5}=85\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":2}]}],"id_ques":2795},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"M\u1ed9t d\u00e2y c\u00e1p \u0111i\u1ec7n b\u1eb1ng \u0111\u1ed3ng c\u00f3 l\u00f5i l\u00e0 15 s\u1ee3i d\u00e2y \u0111\u1ed3ng nh\u1ecf xo\u1eafn l\u1ea1i v\u1edbi nhau. \u0110i\u1ec7n tr\u1edf c\u1ee7a m\u1ed7i s\u1ee3i d\u00e2y \u0111\u1ed3ng nh\u1ecf n\u00e0y l\u00e0 0,9\u2126. T\u00ednh \u0111i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y c\u00e1p \u0111i\u1ec7n n\u00e0y.","select":["A. 0,6\u2126","B. 6\u2126","C. 0,06\u2126","D. 0,04\u2126"],"hint":"","explain":"<span class='basic_left'>Do ti\u1ebft di\u1ec7n d\u00e2y t\u0103ng l\u00ean 15 l\u1ea7n n\u00ean \u0111i\u1ec7n tr\u1edf gi\u1ea3m 15 l\u1ea7n ngh\u0129a l\u00e0 \u0111i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y c\u00e1p \u0111i\u1ec7n l\u00e0 $R=\\dfrac{0,9}{15}=0,06\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2796},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"Hai d\u00e2y d\u1eabn \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t lo\u1ea1i v\u1eadt li\u1ec7u, c\u00f3 chi\u1ec1u d\u00e0i, ti\u1ebft di\u1ec7n v\u00e0 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 $l_{1}^{{}}$, $S_{1}^{{}}$, $R_{1}^{{}}$ v\u00e0 $l_{2}^{{}}$, $S_{2}^{{}}$, $R_{2}^{{}}$. H\u1ec7 th\u1ee9c n\u00e0o d\u01b0\u1edbi \u0111\u00e2y l\u00e0 \u0111\u00fang?","select":["A. $R_{1}^{{}}l_{1}^{{}}S_{1}^{{}}=R_{2}^{{}}l_{2}^{{}}S_{2}^{{}}$","B. $\\dfrac{R_{1}^{{}}}{S_{1}^{{}}}l_{1}^{{}}=\\dfrac{R_{2}^{{}}}{S_{2}^{{}}}l_{2}^{{}}$","C. $\\dfrac{R_{1}^{{}}}{S_{1}^{{}}}l_{1}^{{}}=\\dfrac{S_{2}^{{}}}{R_{2}^{{}}}l_{2}^{{}}$","D. $\\dfrac{l_{1}^{{}}}{R_{1}^{{}}S_{1}^{{}}}=\\dfrac{l_{2}^{{}}}{R_{2}^{{}}S_{2}^{{}}}$"],"hint":"","explain":"<span class='basic_left'>V\u00ec c\u1ea3 2 \u0111i\u1ec7n tr\u1edf l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t v\u1eadt li\u1ec7u n\u00ean ta c\u00f3 \u0111i\u1ec7n tr\u1edf su\u1ea5t c\u1ee7a ch\u00fang b\u1eb1ng nhau: <br\/>$\\dfrac{l_{1}^{{}}}{R_{1}^{{}}S_{1}^{{}}}=\\dfrac{l_{2}^{{}}}{R_{2}^{{}}S_{2}^{{}}}$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":1}]}],"id_ques":2797},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"M\u1ed9t d\u00e2y d\u1eabn b\u1eb1ng \u0111\u1ed3ng c\u00f3 \u0111i\u1ec7n tr\u1edf 6,8\u03a9 v\u1edbi l\u00f5i g\u1ed3m 20 s\u1ee3i \u0111\u1ed3ng m\u1ea3nh. T\u00ednh \u0111i\u1ec7n tr\u1edf c\u1ee7a m\u1ed7i s\u1ee3i d\u00e2y m\u1ea3nh n\u00e0y, cho r\u1eb1ng ch\u00fang c\u00f3 ti\u1ebft di\u1ec7n nh\u01b0 nhau.","select":["A. 50 \u03a9","B. 60 \u03a9","C. 75 \u03a9","D. 136 \u03a9"],"hint":"","explain":"<span class='basic_left'>V\u00ec d\u00e2y d\u1eabn v\u1edbi l\u00f5i g\u1ed3m 20 s\u1ee3i \u0111\u1ed3ng m\u1ea3nh, n\u00ean \u0111i\u1ec7n tr\u1edf c\u1ee7a m\u1ed7i l\u00f5i s\u1ebd b\u1eb1ng $\\dfrac{1}{20}$ \u0111i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y.<br\/>\u0110i\u1ec7n tr\u1edf c\u1ee7a m\u1ed7i d\u00e2y m\u1ea3nh l\u00e0: $R=6,8\\times 20=136\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":2}]}],"id_ques":2798},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"Cu\u1ed9n d\u00e2y th\u1ee9 nh\u1ea5t c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 $R_{1}^{{}}$=20\u2126, \u0111\u01b0\u1ee3c qu\u1ea5n b\u1eb1ng d\u00e2y d\u1eabn c\u00f3 chi\u1ec1u d\u00e0i t\u1ed5ng c\u1ed9ng l\u00e0 $l_{1}^{{}}$=40m v\u00e0 c\u00f3 \u0111\u01b0\u1eddng k\u00ednh ti\u1ebft di\u1ec7n l\u00e0 $d_{1}^{{}}$=0,5mm. D\u00f9ng d\u00e2y d\u1eabn \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng v\u1eadt li\u1ec7u nh\u01b0 cu\u1ed9n d\u00e2y th\u1ee9 nh\u1ea5t, nh\u01b0ng c\u00f3 \u0111\u01b0\u1eddng k\u00ednh ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y l\u00e0 $d_{2}^{{}}$=0,3mm \u0111\u1ec3 qu\u1ea5n m\u1ed9t cu\u1ed9n d\u00e2y th\u1ee9 hai, c\u00f3 \u0111i\u1ec7n tr\u1edf $R_{2}^{{}}$=30\u2126. T\u00ednh chi\u1ec1u d\u00e0i t\u1ed5ng c\u1ed9ng c\u1ee7a d\u00e2y d\u1eabn d\u00f9ng \u0111\u1ec3 qu\u1ea5n cu\u1ed9n d\u00e2y th\u1ee9 hai n\u00e0y.","select":["A. 21 m","B. 21,6m","C. 20,5m","D. 13,6m"],"hint":"","explain":"<span class='basic_left'>Cu\u1ed9n d\u00e2y 1: $S_{1}^{{}}=\\dfrac{3,14\\times {{(d_{1}^{{}})}^{2}}}{4}=\\dfrac{3,14\\times {{(0,5)}^{2}}}{4}=0,19625m{{m}^{2}}$<br\/>Cu\u1ed9n d\u00e2y 2: $S_{2}^{{}}=\\dfrac{3,14\\times {{(d_{2}^{{}})}^{2}}}{4}=\\dfrac{3,14\\times {{\\left( 0,3 \\right)}^{2}}}{4}=0,07065m{{m}^{2}}$<br\/>Ta c\u00f3: $\\dfrac{R_{1}^{{}}}{R_{2}^{{}}}=\\dfrac{l_{1}^{{}}S_{2}^{{}}}{l_{2}^{{}}S_{1}^{{}}}\\Leftrightarrow \\dfrac{20}{30}=\\dfrac{40\\times 0,07065}{l_{2}^{{}}\\times 0,19625}\\Rightarrow l_{2}^{{}}=21,6m$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":2}]}],"id_ques":2799},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"Ng\u01b0\u1eddi ta d\u00f9ng d\u00e2y Nik\u00ealin (m\u1ed9t lo\u1ea1i h\u1ee3p kim) l\u00e0m d\u00e2y nung cho m\u1ed9t b\u1ebfp \u0111i\u1ec7n. N\u1ebfu d\u00f9ng lo\u1ea1i d\u00e2y n\u00e0y v\u1edbi \u0111\u01b0\u1eddng k\u00ednh ti\u1ebft di\u1ec7n l\u00e0 0,6mm th\u00ec c\u1ea7n d\u00e2y c\u00f3 chi\u1ec1u d\u00e0i l\u00e0 2,88m. H\u1ecfi n\u1ebfu kh\u00f4ng thay \u0111\u1ed5i \u0111i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y nung, nh\u01b0ng d\u00f9ng d\u00e2y lo\u1ea1i n\u00e0y v\u1edbi \u0111\u01b0\u1eddng k\u00ednh ti\u1ebft di\u1ec7n l\u00e0 0,4 mm th\u00ec d\u00e2y ph\u1ea3i c\u00f3 chi\u1ec1u d\u00e0i l\u00e0 bao nhi\u00eau?","select":["A. 1,48m","B. 1,36m","C. 1,28m","D. 1,24m"],"hint":"","explain":"<span class='basic_left'>D\u00e2y 1: $S_{1}^{{}}=\\dfrac{3,14\\times {{\\left( d_{1}^{{}} \\right)}^{2}}}{4}=\\dfrac{3,14\\times {{\\left( 0,6 \\right)}^{2}}}{4}=0,2826m{{m}^{2}}$<br\/>D\u00e2y 2: $S_{2}^{{}}=\\dfrac{3,14\\times {{\\left( d_{2}^{{}} \\right)}^{2}}}{4}=\\dfrac{3,14\\times {{\\left( 0,4 \\right)}^{2}}}{4}=0,1256m{{m}^{2}}$<br\/>Chi\u1ec1u d\u00e0i c\u1ee7a s\u1ee3i d\u00e2y c\u00f3 \u0111\u01b0\u1eddng k\u00ednh 0,4mm: $l=\\dfrac{2880\\times 0,1256}{0,2826}=1280mm=1,28m$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2800},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"M\u1ed9t d\u00e2y nh\u00f4m d\u00e0i $l_{1}^{{}}=200m$, ti\u1ebft di\u1ec7n $S_{1}^{{}}=1m{{m}^{2}}$ th\u00ec c\u00f3 \u0111i\u1ec7n tr\u1edf$R_{1}^{{}}$=5,6\u03a9. H\u1ecfi m\u1ed9t d\u00e2y nh\u00f4m kh\u00e1c ti\u1ebft di\u1ec7n $S_{2}^{{}}=2m{{m}^{2}}$ v\u00e0 \u0111i\u1ec7n tr\u1edf $R_{2}^{{}}$=16,8\u03a9 th\u00ec c\u00f3 chi\u1ec1u d\u00e0i $l_{2}^{{}}$ l\u00e0 bao nhi\u00eau?","select":["A. 1000m","B. 1200m","C. 900m","D. 600m"],"hint":"","explain":"<span class='basic_left'>Chi\u1ec1u d\u00e0i c\u1ee7a d\u00e2y nh\u00f4m c\u00f3 ti\u1ebft di\u1ec7n $S_{1}^{{}}=1m{{m}^{2}}$v\u00e0 \u0111i\u1ec7n tr\u1edf $R_{1}^{{}}$=5,6\u03a9.l\u00e0: $l=\\dfrac{16,8}{5,6}l_{1}^{{}}$<br\/>V\u1eady chi\u1ec1u d\u00e0i c\u1ee7a d\u00e2y nh\u00f4m c\u00f3 ti\u1ebft di\u1ec7n $S_{2}^{{}}=2m{{m}^{2}}$v\u00e0 \u0111i\u1ec7n tr\u1edf $R_{2}^{{}}$=16,8\u03a9 l\u00e0: <br\/>$l_{2}^{{}}=2l=2\\times \\dfrac{16,8}{5,6}l_{1}^{{}}=6l_{1}^{{}}=1200m$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":2}]}],"id_ques":2801},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"Hai d\u00e2y d\u1eabn \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t v\u1eadt li\u1ec7u, d\u00e2y th\u1ee9 nh\u1ea5t d\u00e0i h\u01a1n d\u00e2y th\u1ee9 hai 8 l\u1ea7n v\u00e0 c\u00f3 ti\u1ebft di\u1ec7n l\u1edbn g\u1ea5p 2 l\u1ea7n so v\u1edbi d\u00e2y th\u1ee9 hai. H\u1ecfi d\u00e2y th\u1ee9 nh\u1ea5t c\u00f3 \u0111i\u1ec7n tr\u1edf l\u1edbn g\u1ea5p m\u1ea5y l\u1ea7n d\u00e2y th\u1ee9 2.","select":["A. 8 l\u1ea7n","B. 10 l\u1ea7n","C. 4 l\u1ea7n","D. 16 l\u1ea7n"],"hint":"","explain":"<span class='basic_left'>Do d\u00e2y th\u1ee9 nh\u1ea5t d\u00e0i h\u01a1n d\u00e2y th\u1ee9 hai 8 l\u1ea7n v\u00e0 c\u00f3 ti\u1ebft di\u1ec7n l\u1edbn g\u1ea5p 2 l\u1ea7n so v\u1edbi d\u00e2y th\u1ee9 hai. Chi\u1ec1u d\u00e0i l\u1edbn h\u01a1n 8 l\u1ea7n n\u00ean \u0111i\u1ec7n tr\u1edf l\u1edbn h\u01a1n 8 l\u1ea7n, ti\u1ebft di\u1ec7n l\u1edbn g\u1ea5p 2 l\u1ea7n n\u00ean \u0111i\u1ec7n tr\u1edf gi\u1ea3m \u0111i 2 l\u1ea7n. V\u00ec v\u1eady d\u00e2y th\u1ee9 nh\u1ea5t c\u00f3 \u0111i\u1ec7n tr\u1edf l\u1edbn g\u1ea5p 4 l\u1ea7n d\u00e2y th\u1ee9 hai.<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2802},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"M\u1ed9t d\u00e2y \u0111\u1ed3ng d\u00e0i 100m, c\u00f3 ti\u1ebft di\u1ec7n $1m{{m}^{2}}$th\u00ec c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 1,7\u03a9. M\u1ed9t d\u00e2y \u0111\u1ed3ng kh\u00e1c c\u00f3 chi\u1ec1u d\u00e0i 200m, c\u00f3 \u0111i\u1ec7n tr\u1edf 17\u03a9 th\u00ec c\u00f3 ti\u1ebft di\u1ec7n l\u00e0 bao nhi\u00eau?","select":["A. $5m{{m}^{2}}$","B. $0,2m{{m}^{2}}$","C. $0,05m{{m}^{2}}$","D. $20m{{m}^{2}}$"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y \u0111\u1ed3ng th\u1ee9 hai: $R{{_{2}^{{}}}^{'}}=2R_{1}^{{}}=2\\times 1,7=3,4\\Omega $<br\/>Ta c\u00f3: $\\dfrac{{{S}^{'}}_{2}^{{}}}{S_{2}^{{}}}=\\dfrac{R_{2}^{{}}}{R{{_{2}^{{}}}^{'}}}\\Rightarrow S_{2}^{{}}=\\dfrac{S{{_{2}^{{}}}^{'}}\\times R{{_{2}^{{}}}^{'}}}{R_{2}^{{}}}=0,2m{{m}^{2}}$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":2}]}],"id_ques":2803},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"M\u1ed9t d\u00e2y c\u00e1p \u0111i\u1ec7n b\u1eb1ng \u0111\u1ed3ng c\u00f3 l\u00f5i l\u00e0 15 s\u1ee3i d\u00e2y \u0111\u1ed3ng nh\u1ecf xo\u1eafn l\u1ea1i v\u1edbi nhau. \u0110i\u1ec7n tr\u1edf c\u1ee7a m\u1ed7i s\u1ee3i d\u00e2y \u0111\u1ed3ng nh\u1ecf n\u00e0y l\u00e0 0,9\u03a9. T\u00ednh \u0111i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y c\u00e1p \u0111i\u1ec7n n\u00e0y.","select":["A. 0,02 \u03a9","B. 0,04 \u03a9","C. 0,06 \u03a9","D. 0,08 \u03a9"],"hint":"","explain":"<span class='basic_left'>Do ti\u1ebft di\u1ec7n d\u00e2y t\u0103ng l\u00ean 15 l\u1ea7n n\u00ean \u0111i\u1ec7n tr\u1edf gi\u1ea3m 15 l\u1ea7n ngh\u0129a l\u00e0 \u0111i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y c\u00e1p \u0111i\u1ec7n l\u00e0 : $R=\\dfrac{0,9}{15}=0,06\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2804},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"Hai d\u00e2y d\u1eabn b\u1eb1ng \u0111\u1ed3ng c\u00f3 c\u00f9ng chi\u1ec1u d\u00e0i, m\u1ed9t d\u00e2y c\u00f3 ti\u1ebft di\u1ec7n $S_{1}^{{}}$ v\u00e0 \u0111i\u1ec7n tr\u1edf 4\u03a9, d\u00e2y kia c\u00f3 ti\u1ebft di\u1ec7n $S_{2}^{{}}$ v\u00e0 \u0111i\u1ec7n tr\u1edf 12\u03a9. T\u1ec9 s\u1ed1 $\\dfrac{S_{1}^{{}}}{S_{2}^{{}}}$b\u1eb1ng:","select":["A. $\\dfrac{1}{2}$","B. 2","C. $\\dfrac{1}{3}$","D. 3"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi ti\u1ebft di\u1ec7n n\u00ean: $\\dfrac{S_{1}^{{}}}{S_{2}^{{}}}=\\dfrac{R_{2}^{{}}}{R_{1}^{{}}}=3$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":2}]}],"id_ques":2805},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"Ba d\u00e2y d\u1eabn c\u00f3 c\u00f9ng chi\u1ec1u d\u00e0i, c\u00f9ng l\u00e0m b\u1eb1ng \u0111\u1ed3ng. D\u00e2y th\u1ee9 nh\u1ea5t ti\u1ebft di\u1ec7n $S_{1}^{{}}=1m{{m}^{2}}$ c\u00f3 \u0111i\u1ec7n tr\u1edf $R_{1}^{{}}$, d\u00e2y th\u1ee9 ti\u1ebft di\u1ec7n $S_{2}^{{}}=2m{{m}^{2}}$ c\u00f3 \u0111i\u1ec7n tr\u1edf $R_{2}^{{}}$, d\u00e2y th\u1ee9 ba ti\u1ebft di\u1ec7n $S_{3}^{{}}=3m{{m}^{2}}$ c\u00f3 \u0111i\u1ec7n tr\u1edf $R_{3}^{{}}$. C\u00e2u tr\u1ea3 l\u1eddi n\u00e0o d\u01b0\u1edbi \u0111\u00e2y l\u00e0 \u0111\u00fang khi so s\u00e1nh \u0111i\u1ec7n tr\u1edf c\u1ee7a c\u00e1c d\u00e2y d\u1eabn?","select":["A. $R_{3}^{{}}$ > $R_{2}^{{}}$ > $R_{1}^{{}}$","B. $R_{1}^{{}}$ > $R_{3}^{{}}$ > $R_{2}^{{}}$","C. $R_{2}^{{}}$ > $R_{1}^{{}}$> $R_{3}^{{}}$","D. $R_{1}^{{}}$ > $R_{2}^{{}}$ > $R_{3}^{{}}$"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf c\u1ee7a c\u00e1c d\u00e2y d\u1eabn c\u00f3 c\u00f9ng chi\u1ec1u d\u00e0i v\u00e0 \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t lo\u1ea1i v\u1eadt li\u1ec7u th\u00ec t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi ti\u1ebft di\u1ec7n c\u1ee7a m\u1ed7i d\u00e2y.<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":2}]}],"id_ques":2806},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua m\u1ed9t d\u00e2y d\u1eabn thay \u0111\u1ed5i nh\u01b0 th\u1ebf n\u00e0o khi ti\u1ebft di\u1ec7n d\u00e2y gi\u1ea3m \u0111i m\u1ed9t n\u1eeda? Bi\u1ebft r\u1eb1ng hi\u1ec7u \u0111i\u1ec7n th\u1ebf kh\u00f4ng \u0111\u1ed5i.","select":["A. T\u0103ng l\u00ean g\u1ea5p \u0111\u00f4i.","B. Kh\u00f4ng thay \u0111\u1ed5i.","C. Gi\u1ea3m \u0111i m\u1ed9t n\u1eeda.","D. Gi\u1ea3m \u0111i c\u00f2n 1\/4."],"hint":"","explain":"<span class='basic_left'>Khi ti\u1ebft di\u1ec7n gi\u1ea3m \u0111i m\u1ed9t n\u1eeda th\u00ec \u0111i\u1ec7n tr\u1edf t\u0103ng l\u00ean g\u1ea5p \u0111\u00f4i v\u00e0 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n gi\u1ea3m \u0111i m\u1ed9t n\u1eeda.<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2807},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"Hai d\u00e2y d\u1eabn b\u1eb1ng \u0111\u1ed3ng c\u00f3 c\u00f9ng chi\u1ec1u d\u00e0i, ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y th\u1ee9 nh\u1ea5t g\u1ea5p ba l\u1ea7n ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y th\u1ee9 hai, d\u00e2y th\u1ee9 hai c\u00f3 \u0111i\u1ec7n tr\u1edf 6\u03a9. \u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y th\u1ee9 nh\u1ea5t l\u00e0:","select":["A. 2\u03a9.","B. 3\u03a9.","C. 6\u03a9.","D. 18\u03a9."],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi ti\u1ebft di\u1ec7n: $\\dfrac{R_{1}^{{}}}{R_{2}^{{}}}=\\dfrac{S_{2}^{{}}}{S_{1}^{{}}}=\\dfrac{1}{3}\\Rightarrow R_{1}^{{}}=\\dfrac{R_{2}^{{}}\\times 1}{3}=6\\times \\dfrac{1}{3}=2\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A.<\/span><\/span> ","column":2}]}],"id_ques":2808},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"Hai d\u00e2y nh\u00f4m c\u00f3 c\u00f9ng chi\u1ec1u d\u00e0i, m\u1ed9t d\u00e2y ti\u1ebft di\u1ec7n $S_{1}^{{}}=4m{{m}^{2}}$ c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 2\u03a9, d\u00e2y th\u1ee9 hai c\u00f3 \u0111i\u1ec7n tr\u1edf $R_{2}^{{}}$ = 16\u03a9. Ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y th\u1ee9 hai l\u00e0:","select":["A. $0,5m{{m}^{2}}$","B. $0,2m{{m}^{2}}$","C. $0,05m{{m}^{2}}$","D. $20m{{m}^{2}}$"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi ti\u1ebft di\u1ec7n: $\\dfrac{R_{1}^{{}}}{R_{2}^{{}}}=\\dfrac{S_{2}^{{}}}{S_{1}^{{}}}=\\dfrac{1}{8}\\Rightarrow S_{2}^{{}}=\\dfrac{S_{1}^{{}}\\times 1}{8}=4\\times \\dfrac{1}{8}=0,5m{{m}^{2}}$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A.<\/span><\/span> ","column":2}]}],"id_ques":2809},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"M\u1ed9t d\u00e2y d\u1eabn nh\u00f4m c\u00f3 chi\u1ec1u d\u00e0i l, ti\u1ebft di\u1ec7n \u0111\u1ec1u S c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 18\u2126 \u0111\u01b0\u1ee3c g\u1eadp l\u00e0m 3 th\u00e0nh m\u1ed9t d\u00e2y d\u1eabn m\u1edbi c\u00f3 chi\u1ec1u d\u00e0i $\\dfrac{l}{3}$. \u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn m\u1edbi n\u00e0y l\u00e0 bao nhi\u00eau?","select":["A. 4\u2126","B. 6\u2126","C. 8\u2126","D. 2\u2126"],"hint":"","explain":"<span class='basic_left'>Do g\u1eadp ba l\u1ea1i n\u00ean chi\u1ec1u d\u00e0i gi\u1ea3m \u0111i 3 l\u1ea7n v\u00e0 ti\u1ebft di\u1ec7n t\u0103ng g\u1ea5p 3 l\u1ea7n. Chi\u1ec1u d\u00e0i gi\u1ea3m 3 l\u1ea7n n\u00ean \u0111i\u1ec7n tr\u1edf gi\u1ea3m ba l\u1ea7n, ti\u1ebft di\u1ec7n t\u0103ng 3 l\u1ea7n n\u00ean \u0111i\u1ec7n tr\u1edf gi\u1ea3m th\u00eam 3 l\u1ea7n k\u1ebft qu\u1ea3 gi\u1ea3m 9 l\u1ea7n. V\u00ec v\u1eady \u0111i\u1ec7n tr\u1edf d\u00e2y d\u1eabn m\u1edbi l\u00e0 $\\dfrac{18}{9}=2\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":2}]}],"id_ques":2810}],"lesson":{"save":0,"level":2}}