{"segment":[{"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":"X\u00e9t c\u00e1c d\u00e2y d\u1eabn \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t lo\u1ea1i v\u1eadt li\u1ec7u, n\u1ebfu chi\u1ec1u d\u00e0i d\u00e2y d\u1eabn gi\u1ea3m \u0111i 5 l\u1ea7n v\u00e0 ti\u1ebft di\u1ec7n t\u0103ng 2 l\u1ea7n th\u00ec \u0111i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn thay \u0111\u1ed5i nh\u01b0 th\u1ebf n\u00e0o?","select":["A. \u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn t\u0103ng l\u00ean 10 l\u1ea7n.","B. \u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn gi\u1ea3m \u0111i 10 l\u1ea7n.","C. \u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn t\u0103ng l\u00ean 2,5 l\u1ea7n.","D. \u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn gi\u1ea3m \u0111i 2,5 l\u1ea7n."],"hint":"","explain":"<span class='basic_left'>X\u00e9t c\u00e1c d\u00e2y d\u1eabn \u0111\u01b0\u1ee3c l\u00e0m t\u1eeb c\u00f9ng m\u1ed9t lo\u1ea1i v\u1eadt li\u1ec7u,<br\/>Ta th\u1ea5y: $R=\\rho \\times \\dfrac{l}{S}$<br\/>N\u1ebfu chi\u1ec1u d\u00e0i d\u00e2y d\u1eabn gi\u1ea3m \u0111i 5 l\u1ea7n v\u00e0 ti\u1ebft di\u1ec7n t\u0103ng 2 l\u1ea7n th\u00ec \u0111i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn thay \u0111\u1ed5i : $R=\\rho \\times \\dfrac{l}{5\\times 2S}=\\rho \\times \\dfrac{l}{10S}$<br\/>\u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn gi\u1ea3m \u0111i 10 l\u1ea7n.<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":2}]}],"id_ques":2851},{"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":"C\u00e2u ph\u00e1t bi\u1ec3u n\u00e0o d\u01b0\u1edbi \u0111\u00e2y v\u1ec1 m\u1ed1i quan h\u1ec7 gi\u1eefa hi\u1ec7u \u0111i\u1ec7n th\u1ebf U gi\u1eefa hai \u0111\u1ea7u m\u1ed9t \u0111o\u1ea1n m\u1ea1ch c\u00f3 \u0111i\u1ec7n tr\u1edf R v\u00e0 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n I ch\u1ea1y qua \u0111o\u1ea1n m\u1ea1ch l\u00e0 kh\u00f4ng \u0111\u00fang?","select":["A. Hi\u1ec7u \u0111i\u1ec7n th\u1ebf U b\u1eb1ng t\u00edch s\u1ed1 gi\u1eefa c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n I v\u00e0 \u0111i\u1ec7n tr\u1edf R c\u1ee7a \u0111o\u1ea1n m\u1ea1ch.","B. \u0110i\u1ec7n tr\u1edf R c\u1ee7a \u0111o\u1ea1n m\u1ea1ch kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf U gi\u1eefa hai \u0111\u1ea7u \u0111o\u1ea1n m\u1ea1ch v\u00e0 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua \u0111o\u1ea1n m\u1ea1ch \u0111\u00f3.","C. C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n I t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi hi\u1ec7u \u0111i\u1ec7n th\u1ebf U v\u00e0 t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111i\u1ec7n tr\u1edf R c\u1ee7a \u0111o\u1ea1n m\u1ea1ch.","D. \u0110i\u1ec7n tr\u1edf R t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi hi\u1ec7u \u0111i\u1ec7n th\u1ebf U v\u00e0 t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n I ch\u1ea1y qua \u0111o\u1ea1n m\u1ea1ch."],"hint":"","explain":"<span class='basic_left'>M\u1ed1i quan h\u1ec7 gi\u1eefa hi\u1ec7u \u0111i\u1ec7n th\u1ebf U gi\u1eefa hai \u0111\u1ea7u m\u1ed9t \u0111o\u1ea1n m\u1ea1ch c\u00f3 \u0111i\u1ec7n tr\u1edf R v\u00e0 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n I ch\u1ea1y qua \u0111o\u1ea1n m\u1ea1ch l\u00e0:<br\/>Hi\u1ec7u \u0111i\u1ec7n th\u1ebf U b\u1eb1ng t\u00edch s\u1ed1 gi\u1eefa c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n I v\u00e0 \u0111i\u1ec7n tr\u1edf R c\u1ee7a \u0111o\u1ea1n m\u1ea1ch.<br\/>\u0110i\u1ec7n tr\u1edf R c\u1ee7a \u0111o\u1ea1n m\u1ea1ch kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf U gi\u1eefa hai \u0111\u1ea7u \u0111o\u1ea1n m\u1ea1ch v\u00e0 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua \u0111o\u1ea1n m\u1ea1ch \u0111\u00f3.<br\/>C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n I t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi hi\u1ec7u \u0111i\u1ec7n th\u1ebf U v\u00e0 t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi \u0111i\u1ec7n tr\u1edf R c\u1ee7a \u0111o\u1ea1n m\u1ea1ch.<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":1}]}],"id_ques":2852},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/3.jpg'\/><\/center>Hai b\u00f3ng \u0111\u00e8n $\u0110_1$ v\u00e0 $\u0110_2$ c\u00f3 hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{U}_{1}}=1,5V$v\u00e0 ${{U}_{2}}=6V$; khi s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{R}_{1}}=1,5\\Omega $v\u00e0 ${{R}_{2}}=8\\Omega $. Hai \u0111\u00e8n n\u00e0y \u0111\u01b0\u1ee3c m\u1eafc c\u00f9ng v\u1edbi m\u1ed9t bi\u1ebfn tr\u1edf v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf U=7,5V theo s\u01a1 \u0111\u1ed3 h\u00ecnh v\u1ebd.<br\/>a. H\u1ecfi ph\u1ea3i \u0111i\u1ec1u ch\u1ec9nh bi\u1ebfn tr\u1edf c\u00f3 gi\u00e1 tr\u1ecb bao nhi\u00eau \u0111\u1ec3 hai \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng? <br\/>b. Bi\u1ebfn tr\u1edf n\u00f3i tr\u00ean \u0111\u01b0\u1ee3c qu\u1ea5n b\u1eb1ng d\u00e2y nik\u00ealin c\u00f3 \u0111i\u1ec7n tr\u1edf su\u1ea5t l\u00e0 $0,4\\times {{10}^{-6}}\\Omega m$, c\u00f3 \u0111\u1ed9 d\u00e0i t\u1ed5ng c\u1ed9ng l\u00e0 19,64m v\u00e0 \u0111\u01b0\u1eddng k\u00ednh ti\u1ebft di\u1ec7n l\u00e0 0,5mm. H\u1ecfi gi\u00e1 tr\u1ecb c\u1ee7a bi\u1ebfn tr\u1edf t\u00ednh \u0111\u01b0\u1ee3c \u1edf c\u00e2u a tr\u00ean \u0111\u00e2y chi\u1ebfm bao nhi\u00eau ph\u1ea7n tr\u0103m so v\u1edbi \u0111i\u1ec7n tr\u1edf l\u1edbn nh\u1ea5t c\u1ee7a bi\u1ebfn tr\u1edf n\u00e0y? ","select":["A. ${{R}_{b}}=24\\Omega $, 60%","B. ${{R}_{b}}=24\\Omega $, 40%","C. ${{R}_{b}}=40\\Omega $, 40%","D. ${{R}_{b}}=40\\Omega $, 60%"],"hint":"","explain":"<span class='basic_left'><br\/>a.C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n m\u1ea1ch ch\u00ednh: $I={{I}_{1}}=\\dfrac{{{U}_{1}}}{{{R}_{1}}}=\\dfrac{1,5}{1,5}=1A$<br\/>\u0110i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u0111\u01b0\u01a1ng c\u1ee7a \u0111o\u1ea1n m\u1ea1ch: ${{R}_{td}}=\\dfrac{U}{I}=\\dfrac{7,5}{1}=7,5\\Omega $<br\/>\u0110i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u0111\u01b0\u01a1ng c\u1ee7a \u0111o\u1ea1n m\u1ea1ch m\u1eafc song song g\u1ed3m ${{R}_{2}}$ m\u1eafc song song v\u1edbi bi\u1ebfn tr\u1edf theo c\u00f4ng th\u1ee9c: ${{R}_{td}}={{R}_{1}}+{{R}_{2b}}\\Rightarrow {{R}_{2b}}={{R}_{td}}-{{R}_{1}}=7,5-1,5=6\\Omega $<br\/>\u0110i\u1ec7n tr\u1edf ${{R}_{b}}$ theo c\u00f4ng th\u1ee9c: ${{R}_{b}}=\\dfrac{{{R}_{2}}\\times {{R}_{2b}}}{{{R}_{2}}+{{R}_{2b}}}=24\\Omega $ <br\/>b.<br\/>Ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y: $S=3,14\\times \\dfrac{{{d}^{2}}}{4}=3,14\\times \\dfrac{{{\\left( 0,5\\times {{10}^{-3}} \\right)}^{2}}}{4}=0,169\\times {{10}^{-6}}{{m}^{2}}$<br\/>\u0110i\u1ec7n tr\u1edf l\u1edbn nh\u1ea5t c\u1ee7a bi\u1ebfn tr\u1edf theo c\u00f4ng th\u1ee9c:<br\/> ${{R}_{b\\max }}=\\rho \\times \\dfrac{l}{S}=0,4\\times {{10}^{-6}}\\times \\dfrac{19,64}{0,169\\times {{10}^{-6}}}=40\\Omega $<br\/>Ti\u1ebfp theo t\u00ednh ph\u1ea7n tr\u0103m theo c\u00f4ng th\u1ee9c: $\\dfrac{{{R}_{b}}}{{{R}_{b\\max }}}\\times 100%=60%$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A.<\/span><\/span> ","column":2}]}],"id_ques":2853},{"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 b\u00f3ng \u0111\u00e8n khi s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 ${{R}_{1}}=7,5\\Omega $v\u00e0 ${{R}_{2}}=4,5\\Omega $. D\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua hai \u0111\u00e8n \u0111\u1ec1u c\u00f3 c\u01b0\u1eddng \u0111\u1ed9 \u0111\u1ecbnh m\u1ee9c l\u00e0 I=0,8A. Hai \u0111\u00e8n n\u00e0y \u0111\u01b0\u1ee3c m\u1eafc n\u1ed1i ti\u1ebfp v\u1edbi nhau v\u00e0 v\u1edbi m\u1ed9t \u0111i\u1ec7n tr\u1edf ${{R}_{3}}$ \u0111\u1ec3 m\u1eafc v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf U=12V. T\u00ednh ${{R}_{3}}$ \u0111\u1ec3 hai \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng.","select":["A. 1\u2126","B. 2\u2126","C. 3\u2126","D. 4\u2126"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u0111\u01b0\u01a1ng c\u1ee7a \u0111o\u1ea1n m\u1ea1ch l\u00e0: ${{R}_{td}}=\\dfrac{U}{I}=\\dfrac{12}{0,8}=15\\Omega $<br\/>\u0110\u1ec3 \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng th\u00ec: ${{R}_{3}}=15-\\left( 7,5+4,5 \\right)=3\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2854},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/5.jpg'\/><\/center>Cho m\u1ea1ch \u0111i\u1ec7n c\u00f3 s\u01a1 \u0111\u1ed3 nh\u01b0 h\u00ecnh v\u1ebd, trong \u0111\u00f3 hi\u1ec7u \u0111i\u1ec7n th\u1ebf gi\u1eefa hai \u0111i\u1ec3m A v\u00e0 B \u0111\u01b0\u1ee3c gi\u1eef kh\u00f4ng \u0111\u1ed5i v\u00e0 \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng khi bi\u1ebfn tr\u1edf c\u00f3 \u0111i\u1ec7n tr\u1edf b\u1eb1ng 0. C\u00e2u ph\u00e1t bi\u1ec3u n\u00e0o d\u01b0\u1edbi \u0111\u00e2y l\u00e0 \u0111\u00fang? ","select":["A. \u0110\u00e8n s\u00e1ng m\u1ea1nh l\u00ean khi di chuy\u1ec3n con ch\u1ea1y c\u1ee7a bi\u1ebfn tr\u1edf v\u1ec1 \u0111\u1ea7u M.","B. \u0110\u00e8n s\u00e1ng y\u1ebfu \u0111i khi di chuy\u1ec3n con ch\u1ea1y c\u1ee7a bi\u1ebfn tr\u1edf v\u1ec1 \u0111\u1ea7u M.","C. \u0110\u00e8n s\u00e1ng m\u1ea1nh l\u00ean khi di chuy\u1ec3n con ch\u1ea1y c\u1ee7a bi\u1ebfn tr\u1edf v\u1ec1 \u0111\u1ea7u N.","D. C\u1ea3 ba c\u00e2u tr\u00ean \u0111\u1ec1u kh\u00f4ng \u0111\u00fang."],"hint":"","explain":"<span class='basic_left'>\u0110\u00e8n s\u00e1ng m\u1ea1nh l\u00ean khi chuy\u1ec3n con ch\u1ea1y c\u1ee7a bi\u1ebfn tr\u1edf v\u1ec1 \u0111\u1ea7u M. V\u00ec d\u00f2ng \u0111i\u1ec7n c\u00f3 chi\u1ec1u \u0111i t\u1eeb c\u1ef1c (+) qua d\u00e2y d\u1eabn qua c\u00e1c thi\u1ebft b\u1ecb r\u1ed3i v\u1ec1 c\u1ef1c (-) n\u00ean \u1edf \u0111\u1ea7u M khi con ch\u1ea1y ch\u01b0a d\u1ecbch chuy\u1ec3n chi\u1ec1u d\u00e0i ch\u01b0a thay \u0111\u1ed5i th\u00ec \u0111i\u1ec7n tr\u1edf l\u00e0 nh\u1ecf nh\u1ea5t n\u00ean \u0111\u00e8n s\u00e1ng nh\u1ea5t.<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A.<\/span><\/span> ","column":1}]}],"id_ques":2855},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/6.jpg'\/><\/center>Trong m\u1ea1ch \u0111i\u1ec7n c\u00f3 s\u01a1 \u0111\u1ed3 v\u1ebd \u1edf h\u00ecnh v\u1ebd, ngu\u1ed3n \u0111i\u1ec7n c\u00f3 hi\u1ec7u \u0111i\u1ec7n th\u1ebf kh\u00f4ng \u0111\u1ed5i 12V. <br\/>a. \u0110i\u1ec1u ch\u1ec9nh con ch\u1ea1y c\u1ee7a bi\u1ebfn tr\u1edf \u0111\u1ec3 v\u00f4n k\u1ebf ch\u1ec9 6V th\u00ec ampe k\u1ebf ch\u1ec9 0,5A. H\u1ecfi khi \u0111\u00f3 bi\u1ebfn tr\u1edf c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 bao nhi\u00eau? <br\/>b. Ph\u1ea3i \u0111i\u1ec1u ch\u1ec9nh bi\u1ebfn tr\u1edf c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 bao nhi\u00eau \u0111\u1ec3 v\u00f4n k\u1ebf ch\u1ec9 4,5V.","select":["A. 20\u03a9; 24\u03a9","B. 20\u03a9;12\u03a9","C. 12\u03a9; 20\u03a9","D. 12\u03a9;40\u03a9"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf c\u1ee7a bi\u1ebfn tr\u1edf: ${{R}_{b1}}=\\dfrac{U-{{U}_{v}}}{I}=\\dfrac{12-6}{0,5}=12\\Omega $<br\/>C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua \u0111i\u1ec7n tr\u1edf R v\u00e0 bi\u1ebfn tr\u1edf khi \u0111\u00f3 l\u00e0: $I=\\dfrac{{{U}_{V}}}{R}=\\dfrac{4,5}{12}=0,375A$<br\/>\u0110\u1ec3 v\u00f4n k\u1ebf ch\u1ec9 4,5V th\u00ec \u0111i\u1ec7n tr\u1edf c\u1ee7a bi\u1ebfn tr\u1edf khi \u0111\u00f3 l\u00e0: ${{R}_{b2}}=\\dfrac{U}{I}-R=\\dfrac{12}{0,375}-12=20\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2856},{"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 b\u00f3ng \u0111\u00e8n khi s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 ${{R}_{1}}=7,5\\Omega $v\u00e0 ${{R}_{2}}=4,5\\Omega $. D\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua hai \u0111\u00e8n \u0111\u1ec1u c\u00f3 c\u01b0\u1eddng \u0111\u1ed9 \u0111\u1ecbnh m\u1ee9c l\u00e0 I=0,8A. Hai \u0111\u00e8n n\u00e0y \u0111\u01b0\u1ee3c m\u1eafc n\u1ed1i ti\u1ebfp v\u1edbi nhau v\u00e0 v\u1edbi m\u1ed9t \u0111i\u1ec7n tr\u1edf ${{R}_{3}}$ \u0111\u1ec3 m\u1eafc v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf U=12V. \u0110i\u1ec7n tr\u1edf ${{R}_{3}}$ \u0111\u01b0\u1ee3c qu\u1ea5n b\u1eb1ng d\u00e2y Nicrom c\u00f3 \u0111i\u1ec7n tr\u1edf su\u1ea5t $1,1\\times {{10}^{-6}}\\Omega m$v\u00e0 chi\u1ec1u d\u00e0i l\u00e0 0,8m. T\u00ednh ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y Nicrom n\u00e0y.","select":["A. $3,6m{{m}^{2}}$","B. $2,4m{{m}^{2}}$","C. $0,45m{{m}^{2}}$","D. $0,29m{{m}^{2}}$"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u0111\u01b0\u01a1ng c\u1ee7a \u0111o\u1ea1n m\u1ea1ch l\u00e0: ${{R}_{td}}=\\dfrac{U}{I}=\\dfrac{12}{0,8}=15\\Omega $<br\/>\u0110\u1ec3 \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng th\u00ec: ${{R}_{3}}=15-\\left( 7,5+4,5 \\right)=3\\Omega $<br\/>Ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y nicrom l\u00e0: $S=\\rho \\times \\dfrac{l}{R}=1,1\\times {{10}^{-6}}\\times \\dfrac{0,8}{3}=0,29\\times {{10}^{-6}}{{m}^{2}}=0,29m{{m}^{2}}$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":2}]}],"id_ques":2857},{"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 lo\u1ea1i v\u1eadt li\u1ec7u, d\u00e2y th\u1ee9 nh\u1ea5t c\u00f3 \u0111i\u1ec7n tr\u1edf ${{R}_{1}}=15\\Omega $, c\u00f3 chi\u1ec1u d\u00e0i ${{l}_{1}}=24m$v\u00e0 c\u00f3 ti\u1ebft di\u1ec7n ${{S}_{2}}=0,2m{{m}^{2}}$, d\u00e2y th\u1ee9 hai c\u00f3 \u0111i\u1ec7n tr\u1edf ${{R}_{2}}=10\\Omega $, chi\u1ec1u d\u00e0i ${{l}_{2}}=30m$. T\u00ednh ti\u1ebft di\u1ec7n ${{S}_{2}}$ c\u1ee7a d\u00e2y.","select":["A. $0,48m{{m}^{2}}$","B. $0,24m{{m}^{2}}$","C. $0,375m{{m}^{2}}$","D. $0,75m{{m}^{2}}$"],"hint":"","explain":"<span class='basic_left'>Ta c\u00f3 t\u1ec9 l\u1ec7: $\\dfrac{{{R}_{1}}}{{{R}_{2}}}=\\dfrac{{{l}_{1}}}{{{S}_{1}}}\\times \\dfrac{{{S}_{2}}}{{{l}_{2}}}\\Leftrightarrow \\dfrac{15}{10}=\\dfrac{24\\times {{S}_{1}}}{0,2\\times 30}\\Rightarrow {{S}_{2}}=0,375m{{m}^{2}}$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2858},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/9.jpg'\/><\/center>Hai b\u00f3ng \u0111\u00e8n c\u00f3 c\u00f9ng hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c l\u00e0 ${{U}_{1}}=6V$, khi \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{R}_{1}}=8\\Omega $v\u00e0 ${{R}_{2}}=12\\Omega $. C\u1ea7n m\u1eafc hai b\u00f3ng \u0111\u00e8n v\u1edbi m\u1ed9t bi\u1ebfn tr\u1edf c\u00f3 hi\u1ec7u \u0111i\u1ec7n th\u1ebf U = 9V \u0111\u1ec3 hai \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng. T\u00ednh \u0111i\u1ec7n tr\u1edf c\u1ee7a bi\u1ebfn tr\u1edf.","select":["A. 1,2\u2126","B. 2,4\u2126","C. 3,6\u2126","D. 4,8\u2126"],"hint":"","explain":"<span class='basic_left'>C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n qua \u0111\u00e8n 1 l\u00e0: ${{I}_{1}}=\\dfrac{{{U}_{1}}}{{{R}_{1}}}=\\dfrac{6}{8}=0,75A$<br\/>C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n qua \u0111\u00e8n 2 l\u00e0: ${{I}_{2}}=\\dfrac{{{U}_{2}}}{{{R}_{2}}}=\\dfrac{6}{12}=0,5A$<br\/>C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n qua m\u1ea1ch ch\u00ednh l\u00e0: $I={{I}_{1}}+{{I}_{2}}=1,25A$<br\/>\u0110i\u1ec7n tr\u1edf c\u1ee7a bi\u1ebfn tr\u1edf l\u00e0: ${{R}_{b}}=\\dfrac{U-{{U}_{1}}}{I}=\\dfrac{9-6}{1,25}=2,4\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":2}]}],"id_ques":2859},{"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 b\u00f3ng \u0111\u00e8n c\u00f3 c\u00f9ng hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c l\u00e0 ${{U}_{1}}=6V$, khi \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{R}_{1}}=8\\Omega $v\u00e0 ${{R}_{2}}=12\\Omega $. C\u1ea7n m\u1eafc hai b\u00f3ng \u0111\u00e8n v\u1edbi m\u1ed9t bi\u1ebfn tr\u1edf c\u00f3 hi\u1ec7u \u0111i\u1ec7n th\u1ebf U = 9V \u0111\u1ec3 hai \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng. Bi\u1ebfn tr\u1edf \u0111\u01b0\u1ee3c qu\u1ea5n b\u1eb1ng d\u00e2y h\u1ee3p kim Nik\u00ealin c\u00f3 \u0111i\u1ec7n tr\u1edf su\u1ea5t l\u00e0 $0,4\\times {{10}^{-6}}\\Omega m$, ti\u1ebft di\u1ec7n tr\u00f2n, chi\u1ec1u d\u00e0i 2m. T\u00ednh \u0111\u01b0\u1eddng k\u00ednh ti\u1ebft di\u1ec7n d c\u1ee7a d\u00e2y h\u1ee3p kim n\u00e0y, bi\u1ebft r\u1eb1ng hi\u1ec7u \u0111i\u1ec7n th\u1ebf l\u1edbn nh\u1ea5t \u0111\u01b0\u1ee3c ph\u00e9p \u0111\u1eb7t v\u00e0o hai \u0111\u1ea7u c\u1ee7a bi\u1ebfn tr\u1edf l\u00e0 30V v\u00e0 khi \u0111\u00f3 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua bi\u1ebfn tr\u1edf c\u00f3 c\u01b0\u1eddng \u0111\u1ed9 l\u00e0 2A.","select":["A. 0,13mm","B. 0,26mm","C. 0,39mm","D. 0,52mm"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf l\u1edbn nh\u1ea5t c\u1ee7a bi\u1ebfn tr\u1edf l\u00e0: ${{R}_{\\max }}=\\dfrac{{{U}_{\\max }}}{{{I}_{\\max }}}=\\dfrac{30}{2}=15\\Omega $<br\/>Ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y l\u00e0: $S=\\rho \\times \\dfrac{l}{R}=0,4\\times {{10}^{-6}}\\times \\dfrac{2}{15}=0,053\\times {{10}^{-6}}{{m}^{2}}=0,053m{{m}^{2}}$<br\/>V\u00ec d\u00e2y d\u1eabn c\u00f3 ti\u1ebft di\u1ec7n tr\u00f2n n\u00ean: $S=\\dfrac{3,14\\times {{d}^{2}}}{4}\\Rightarrow d=2\\times \\sqrt{\\dfrac{S}{3,14}}=2\\times \\sqrt{\\dfrac{0,053}{3,14}}=0,26mm$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":2}]}],"id_ques":2860},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/11.jpg'\/><\/center>Hai b\u00f3ng \u0111\u00e8n c\u00f3 hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c l\u1ea7n l\u01b0\u1ee3t l\u00e0 ${{U}_{1}}=6V$, ${{U}_{2}}=3V$v\u00e0 khi s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{R}_{1}}=5\\Omega $v\u00e0 ${{R}_{2}}=3\\Omega $. C\u1ea7n m\u1eafc hai \u0111\u00e8n n\u00e0y v\u1edbi m\u1ed9t bi\u1ebfn tr\u1edf v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf U = 9V \u0111\u1ec3 hai \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng nh\u01b0 h\u00ecnh v\u1ebd. T\u00ednh \u0111i\u1ec7n tr\u1edf c\u1ee7a bi\u1ebfn tr\u1edf khi \u0111\u00f3.","select":["A. 5\u2126","B. 10\u2126","C. 15\u2126","D. 20\u2126"],"hint":"","explain":"<span class='basic_left'>C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua \u0111\u00e8n 1 l\u00e0: ${{I}_{1}}=\\dfrac{{{U}_{1}}}{{{R}_{1}}}=\\dfrac{6}{5}=1,2A$<br\/>C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua bi\u1ebfn tr\u1edf l\u00e0: ${{I}_{b}}={{I}_{1}}-{{I}_{2}}=0,2A$<br\/>\u0110i\u1ec7n tr\u1edf c\u1ee7a bi\u1ebfn tr\u1edf: ${{R}_{b}}=\\dfrac{{{U}_{2}}}{{{I}_{b}}}=15\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2861},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/12.jpg'\/><\/center>Hai b\u00f3ng \u0111\u00e8n c\u00f3 hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c l\u1ea7n l\u01b0\u1ee3t l\u00e0 ${{U}_{1}}=6V$, ${{U}_{2}}=3V$v\u00e0 khi s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{R}_{1}}=5\\Omega $v\u00e0 ${{R}_{2}}=3\\Omega $. C\u1ea7n m\u1eafc hai \u0111\u00e8n n\u00e0y v\u1edbi m\u1ed9t bi\u1ebfn tr\u1edf v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf U = 9V \u0111\u1ec3 hai \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng n\u01b0 h\u00ecnh v\u1ebd. Bi\u1ebfn tr\u1edf n\u00e0y c\u00f3 \u0111i\u1ec7n tr\u1edf l\u1edbn nh\u1ea5t l\u00e0 25\u03a9, \u0111\u01b0\u1ee3c qu\u1ea5n b\u1eb1ng d\u00e2y nicrom c\u00f3 \u0111i\u1ec7n tr\u1edf su\u1ea5t l\u00e0 $1,1\\times {{10}^{-6}}\\Omega m$, c\u00f3 ti\u1ebft di\u1ec7n $0,2m{{m}^{2}}$. T\u00ednh chi\u1ec1u d\u00e0i c\u1ee7a d\u00e2y nicrom n\u00e0y.","select":["A. 2,323m","B. 3,232m","C. 4,545m","D. 5,454m"],"hint":"","explain":"<span class='basic_left'>Chi\u1ec1u d\u00e0i d\u00e2y d\u1eabn d\u00f9ng \u0111\u1ec3 qu\u1ea5n bi\u1ebfn tr\u1edf l\u00e0: $l=\\dfrac{R\\times S}{\\rho }=\\dfrac{25\\times 0,2\\times {{10}^{-6}}}{1,1\\times {{10}^{-6}}}=4,545m$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2862},{"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 b\u00f3ng \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng v\u1edbi hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c ${{U}_{d}}=6V$v\u00e0 khi \u0111\u00f3 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua \u0111\u00e8n c\u00f3 c\u01b0\u1eddng \u0111\u1ed9 ${{I}_{d}}=0,75A$. M\u1eafc b\u00f3ng \u0111\u00e8n v\u1edbi m\u1ed9t bi\u1ebfn tr\u1edf c\u00f3 \u0111i\u1ec7n tr\u1edf l\u1edbn nh\u1ea5t l\u00e0 U = 12V. Ph\u1ea3i \u0111i\u1ec1u ch\u1ec9nh bi\u1ebfn tr\u1edf c\u00f3 \u0111i\u1ec7n tr\u1edf l\u00e0 bao nhi\u00eau \u0111\u1ec3 \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng n\u1ebfu m\u1eafc b\u00f3ng \u0111\u00e8n n\u1ed1i ti\u1ebfp v\u1edbi bi\u1ebfn tr\u1edf v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf U \u0111\u00e3 cho tr\u00ean \u0111\u00e2y?","select":["A. 2\u2126","B. 4\u2126","C. 8\u2126","D. 12\u2126"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf c\u1ee7a bi\u1ebfn tr\u1edf: ${{R}_{b}}=\\dfrac{U-{{U}_{d}}}{{{I}_{d}}}=\\dfrac{12-6}{0,75}=8\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2863},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/14.jpg'\/><\/center>M\u1ed9t b\u00f3ng \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng v\u1edbi hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c ${{U}_{d}}=6V$v\u00e0 khi \u0111\u00f3 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua \u0111\u00e8n c\u00f3 c\u01b0\u1eddng \u0111\u1ed9 ${{I}_{d}}=0,75A$. M\u1eafc b\u00f3ng \u0111\u00e8n v\u1edbi m\u1ed9t bi\u1ebfn tr\u1edf c\u00f3 \u0111i\u1ec7n tr\u1edf l\u1edbn nh\u1ea5t l\u00e0 U = 12V nh\u01b0 h\u00ecnh v\u1ebd. Ph\u1ea7n \u0111i\u1ec7n tr\u1edf ${{R}_{1}}$ c\u1ee7a bi\u1ebfn tr\u1edf l\u00e0 bao nhi\u00eau \u0111\u1ec3 \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng?","select":["A. 3,11\u2126","B. 5,1\u2126","C. 7,2\u2126","D. 11,3\u2126"],"hint":"","explain":"<span class='basic_left'>\u0110\u00e8n \u0111\u01b0\u1ee3c m\u1eafc song song v\u1edbi ph\u1ea7n ${{R}_{1}}$ c\u1ee7a bi\u1ebfn tr\u1edf v\u00e0 \u0111o\u1ea1n m\u1ea1ch song song n\u00e0y \u0111\u01b0\u1ee3c m\u1eafc n\u1ed1i ti\u1ebfp v\u1edbi ph\u1ea7n c\u00f2n l\u1ea1i (16 \u2013 ${{R}_{1}}$) c\u1ee7a bi\u1ebfn tr\u1edf.<br\/>\u0110\u1ec3 \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng th\u00ec hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u1edf hai \u0111\u1ea7u \u0111o\u1ea1n m\u1ea1ch song song l\u00e0 ${{U}_{d}}=6V$ v\u00e0 do \u0111\u00f3 hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u1edf hai \u0111\u1ea7u ph\u1ea7n c\u00f2n l\u1ea1i c\u1ee7a bi\u1ebfn tr\u1edf l\u00e0 $U-{{U}_{d}}=6V$. T\u1eeb \u0111\u00f3 suy ra \u0111i\u1ec7n tr\u1edf c\u1ee7a hai \u0111o\u1ea1n m\u1ea1ch n\u00e0y b\u1eb1ng nhau, ngh\u0129a l\u00e0:<br\/>$\\dfrac{{{R}_{d}}\\times {{R}_{1}}}{{{R}_{d}}+{{R}_{1}}}=16-{{R}_{1}}$<br\/>M\u00e0 ${{R}_{b}}=\\dfrac{{{U}_{d}}}{{{I}_{d}}}=\\dfrac{6}{0,75}=8\\Omega \\Rightarrow {{R}_{1}}\\approx 11,3\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":2}]}],"id_ques":2864},{"time":24,"part":[{"title":"","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"C\u00e2u n\u00e0o sau \u0111\u00e2y sai?","select":["A. Hi\u1ec7u \u0111i\u1ec7n th\u1ebf gi\u1eefa hai \u0111\u1ea7u \u0111o\u1ea1n m\u1ea1ch b\u1eb1ng t\u00edch gi\u1eefa c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua \u0111o\u1ea1n m\u1ea1ch v\u00e0 \u0111i\u1ec7n tr\u1edf c\u1ee7a \u0111o\u1ea1n m\u1ea1ch.","B. \u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi hi\u1ec7u \u0111i\u1ec7n th\u1ebf gi\u1eefa hai \u0111\u1ea7u d\u00e2y v\u00e0 t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua d\u00e2y \u0111\u00f3.","C. \u0110\u1ed1i v\u1edbi \u0111o\u1ea1n m\u1ea1ch n\u1ed1i ti\u1ebfp, hi\u1ec7u \u0111i\u1ec7n th\u1ebf gi\u1eefa hai \u0111\u1ea7u m\u1ed7i \u0111i\u1ec7n tr\u1edf t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi c\u00e1c \u0111i\u1ec7n tr\u1edf.","D. \u0110\u1ed1i v\u1edbi \u0111o\u1ea1n m\u1ea1ch song song, c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua m\u1ed7i m\u1ea1ch r\u1ebd t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi c\u00e1c \u0111i\u1ec7n tr\u1edf."],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf c\u1ee7a d\u00e2y d\u1eabn t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi chi\u1ec1u d\u00e0i, t\u1ec9 l\u1ec7 ngh\u1ecbch v\u1edbi ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y v\u00e0 ph\u1ee5 thu\u1ed9c v\u00e0o v\u1eadt li\u1ec7u l\u00e0m d\u00e2y.<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":1}]}],"id_ques":2865},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/16.jpg'\/><\/center>Hai b\u00f3ng \u0111\u00e8n c\u00f3 c\u00f9ng hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c l\u00e0 ${{U}_{1}}={{U}_{2}}=6V$; khi s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{R}_{1}}=12\\Omega $v\u00e0 ${{R}_{2}}=8\\Omega $. M\u1eafc hai \u0111\u00e8n c\u00f9ng v\u1edbi m\u1ed9t bi\u1ebfn tr\u1edf v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf kh\u00f4ng \u0111\u1ed5i U = 9V \u0111\u1ec3 hai \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng nh\u01b0 h\u00ecnh v\u1ebd. T\u00ednh gi\u00e1 tr\u1ecb c\u1ee7a bi\u1ebfn tr\u1edf khi hai \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng.","select":["A. 2,4\u2126","B. 12\u2126","C. 24\u2126","D. 1,2\u2126"],"hint":"","explain":"<span class='basic_left'>C\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n qua ${{R}_{1}}$, ${{R}_{2}}$ v\u00e0 to\u00e0n m\u1ea1ch: ${{I}_{1}}=\\dfrac{{{U}_{1}}}{{{R}_{1}}}=\\dfrac{6}{12}=0,5A$<br\/>${{I}_{2}}=\\dfrac{{{U}_{2}}}{{{R}_{2}}}=\\dfrac{6}{8}=0,75A$ $\\Rightarrow {{I}_{12}}={{I}_{b}}={{I}_{1}}+{{I}_{2}}=1,25A$<br\/>Ta c\u00f3: ${{R}_{12}}=\\dfrac{{R}_{1}}\\times {{R}_{2}}}{{{R}_{1}}+{{R}_{2}}}=\\dfrac{18\\times 2}{12+8}=4,8\\Omega $<br\/>\u0110i\u1ec7n tr\u1edf to\u00e0n m\u1ea1ch: $R=\\dfrac{U}{I}=\\dfrac{9}{1,25}=7,2\\Omega $<br\/>\u0110i\u1ec7n tr\u1edf c\u1ee7a bi\u1ebfn tr\u1edf: ${{R}_{b}}=R-{{R}_{12}}=7,2-4,8=2,4\\Omega $<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A.<\/span><\/span> ","column":2}]}],"id_ques":2866},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/17.jpg'\/><\/center>Hai b\u00f3ng \u0111\u00e8n c\u00f3 c\u00f9ng hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c l\u00e0 ${{U}_{1}}={{U}_{2}}=6V$; khi s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{R}_{1}}=12\\Omega $ v\u00e0 ${{R}_{2}}=8\\Omega $. M\u1eafc hai \u0111\u00e8n c\u00f9ng v\u1edbi m\u1ed9t bi\u1ebfn tr\u1edf v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf kh\u00f4ng \u0111\u1ed5i U = 9V \u0111\u1ec3 hai \u0111\u00e8n s\u00e1ng b\u00ecnh th\u01b0\u1eddng nh\u01b0 h\u00ecnh v\u1ebd. Bi\u1ebfn tr\u1edf n\u00e0y \u0111\u01b0\u1ee3c qu\u1ea5n b\u1eb1ng d\u00e2y nicrom c\u00f3 \u0111i\u1ec7n tr\u1edf su\u1ea5t l\u00e0 $1,1\\times {{10}^{-6}}\\Omega m$v\u00e0 c\u00f3 ti\u1ebft di\u1ec7n $0,8m{{m}^{2}}$. T\u00ednh \u0111\u1ed9 d\u00e0i t\u1ed5ng c\u1ed9ng c\u1ee7a d\u00e2y qu\u1ea5n bi\u1ebfn tr\u1edf n\u00e0y, bi\u1ebft r\u1eb1ng n\u00f3 c\u00f3 gi\u00e1 tr\u1ecb l\u1edbn nh\u1ea5t ${{R}_{bm}}=15{{R}_{b}}$, trong \u0111\u00f3 ${{R}_{b}}$ l\u00e0 gi\u00e1 tr\u1ecb t\u00ednh \u0111\u01b0\u1ee3c \u1edf c\u00e2u 16 tr\u00ean \u0111\u00e2y.","select":["A. 12,6m","B. 26,2m","C. 21,6m","D. 62,2m"],"hint":"","explain":"<span class='basic_left'>\u0110i\u1ec7n tr\u1edf l\u1edbn nh\u1ea5t c\u1ee7a bi\u1ebfn tr\u1edf: ${{R}_{bm}}=15{{R}_{b}}=15\\times 2,4=36\\Omega $<br\/>\u0110\u1ed9 d\u00e0i d\u00e2y cu\u1ed1n l\u00e0m bi\u1ebfn tr\u1edf: $l=\\dfrac{R\\times S}{\\rho }=\\dfrac{36\\times 0,8\\times {{10}^{-6}}}{1,1\\times {{10}^{-6}}}=26,2m$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":2}]}],"id_ques":2867},{"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":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/vatly/bai11/lv2/img\/18.jpg'\/><\/center>Ba b\u00f3ng \u0111\u00e8n \u01101, \u01102, \u01103 c\u00f3 hi\u1ec7u \u0111i\u1ec7n th\u1ebf \u0111\u1ecbnh m\u1ee9c t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{U}_{1}}=3V$, ${{U}_{2}}={{U}_{3}}=6V$v\u00e0 khi s\u00e1ng b\u00ecnh th\u01b0\u1eddng c\u00f3 \u0111i\u1ec7n tr\u1edf t\u01b0\u01a1ng \u1ee9ng l\u00e0 ${{R}_{1}}=2\\Omega $, ${{R}_{2}}=6\\Omega $, ${{R}_{3}}=12\\Omega $. M\u1eafc ba b\u00f3ng \u0111\u00e8n n\u00e0y v\u00e0o hi\u1ec7u \u0111i\u1ec7n th\u1ebf U = 9V \u0111\u1ec3 c\u00e1c \u0111\u00e8n kh\u00e1c \u0111\u1ec1u s\u00e1ng b\u00ecnh th\u01b0\u1eddng nh\u01b0 h\u00ecnh v\u1ebd. Thay \u0111\u00e8n \u01103 b\u1eb1ng cu\u1ed9n d\u00e2y \u0111i\u1ec7n tr\u1edf \u0111\u01b0\u1ee3c qu\u1ea5n b\u1eb1ng d\u00e2y manganin c\u00f3 \u0111i\u1ec7n tr\u1edf su\u1ea5t $0,43\\times {{10}^{-6}}\\Omega m$v\u00e0 c\u00f3 chi\u1ec1u d\u00e0i 8m. T\u00ednh ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y n\u00e0y.","select":["A. $0,42m{{m}^{2}}$","B. $0,29m{{m}^{2}}$","C. $0,35m{{m}^{2}}$","D. $0,5m{{m}^{2}}$"],"hint":"","explain":"<span class='basic_left'>Ti\u1ebft di\u1ec7n c\u1ee7a d\u00e2y cu\u1ed1n l\u00e0m bi\u1ebfn tr\u1edf: <br\/>$S=\\rho \\times \\dfrac{l}{R}=0,43\\times {{10}^{-6}}\\times \\dfrac{8}{12}\\approx 0,29\\times {{10}^{-6}}{{m}^{2}}=0,29m{{m}^{2}}$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span> ","column":2}]}],"id_ques":2868},{"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":"H\u1ec7 th\u1ee9c n\u00e0o d\u01b0\u1edbi \u0111\u00e2y bi\u1ec3u th\u1ecb m\u1ed1i quan h\u1ec7 gi\u1eefa \u0111i\u1ec7n tr\u1edf R c\u1ee7a d\u00e2y d\u1eabn v\u1edbi chi\u1ec1u d\u00e0i l, ti\u1ebft di\u1ec7n S c\u1ee7a d\u00e2y d\u1eabn v\u00e0 v\u1edbi \u0111i\u1ec7n tr\u1edf su\u1ea5t \u03c1 c\u1ee7a v\u1eadt li\u1ec7u l\u00e0m d\u00e2y d\u1eabn","select":["A. $R=\\dfrac{S}{l}\\times \\rho $","B. $R=\\dfrac{l}{S\\times \\rho }$","C. $R=\\dfrac{l\\times S}{\\rho }$","D. $R=\\rho \\times \\dfrac{l}{S}$"],"hint":"","explain":"<span class='basic_left'><br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span><\/span> ","column":2}]}],"id_ques":2869},{"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\u1ea7n l\u00e0m m\u1ed9t bi\u1ebfn tr\u1edf 20\u03a9 b\u1eb1ng m\u1ed9t d\u00e2y constantan c\u00f3 ti\u1ebft di\u1ec7n $1m{{m}^{2}}$ v\u00e0 \u0111i\u1ec7n tr\u1edf su\u1ea5t $0,5\\times {{10}^{-6}}\\Omega m$. Chi\u1ec1u d\u00e0i c\u1ee7a d\u00e2y constantan l\u00e0:","select":["A. 10m","B. 20m","C. 40m","D. 60m"],"hint":"","explain":"<span class='basic_left'>Chi\u1ec1u d\u00e0i c\u1ee7a d\u00e2y l\u00e0: $l=\\dfrac{R\\times S}{\\rho }=\\dfrac{20\\times 1\\times {{10}^{-6}}}{0,5\\times {{10}^{-6}}}=40m$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span><\/span> ","column":2}]}],"id_ques":2870}],"lesson":{"save":0,"level":2}}