Ph\u1ea7n 1:<\/h2>\n

(\u1ee8NG D\u1ee4NG \u0110\u01af\u1edcNG TR\u00d2N L\u01af\u1ee2NG GI\u00c1C \u0110\u1ec2 GI\u1ea2I B\u00c0I TO\u00c1N D\u00d2NG \u0110I\u1ec6N XOAY CHI\u1ec0U)<\/strong><\/p>\n

A. Ph\u01b0\u01a1ng ph\u00e1p :<\/strong><\/p>\n

1.Ta d\u00f9ng m\u1ed1i li\u00ean h\u1ec7 gi\u1eefa dao \u0111\u1ed9ng \u0111i\u1ec1u ho\u00e0 v\u00e0 chuy\u1ec3n \u0111\u1ed9ng\u00a0<\/strong>tr\u00f2n \u0111\u1ec1u \u0111\u1ec3 t\u00ednh. Theo l\u01b0\u1ee3ng gi\u00e1c :\u00a0<\/strong>\u00a0\u0111\u01b0\u1ee3c bi\u1ec3u di\u1ec5n\u00a0<\/strong>b\u1eb1ng v\u00f2ng tr\u00f2n t\u00e2m O b\u00e1n k\u00ednh U_{0<\/sub>\u00a0, quay v\u1edbi t\u1ed1c \u0111\u1ed9 g\u00f3c \u03c9\u00a0<\/strong><\/p>\n}

<\/strong><\/p>\n

+<\/strong>C\u00f3 2 \u0111i\u1ec3m M ,N chuy\u1ec3n \u0111\u1ed9ng tr\u00f2n \u0111\u1ec1u c\u00f3 h\u00ecnh chi\u1ebfu l\u00ean Ou l\u00e0 u, nh\u01b0ng\u00a0 N c\u00f3 h\u00ecnh chi\u1ebfu l\u00ean Ou c\u00f3 u \u0111ang t\u0103ng (v\u1eadn t\u1ed1c l\u00e0 d\u01b0\u01a1ng) ,c\u00f2n M c\u00f3 h\u00ecnh chi\u1ebfu l\u00ean Ou c\u00f3 u \u0111ang gi\u1ea3m (v\u1eadn t\u1ed1c l\u00e0 \u00e2m )<\/p>\n

+ Ta x\u00e1c \u0111\u1ecbnh xem v\u00e0o th\u1eddi \u0111i\u1ec3m ta x\u00e9t \u0111i\u1ec7n \u00e1p u c\u00f3 gi\u00e1 tr\u1ecb u v\u00e0 \u0111ang bi\u1ebfn \u0111\u1ed5i th\u1ebf n\u00e0o ( v\u00ed d\u1ee5 chi\u1ec1u \u00e2m )<\/p>\n

=> ta ch\u1ecdn M r\u1ed3i t\u00ednh g\u00f3c\u00a0;<\/p>\n

c\u00f2n n\u1ebfu theo chi\u1ec1u d\u01b0\u01a1ng ta ch\u1ecdn N v\u00e0\u00a0 t\u00ednh\u00a0\u00a0 theo l\u01b0\u1ee3ng gi\u00e1c<\/p>\n

2. D\u00f2ng \u0111i\u1ec7n xoay chi\u1ec1u\u00a0i<\/em>\u00a0= I_{0<\/sub>cos(2\u03c0<\/strong>ft + \u03c6<\/strong>i<\/sub><\/strong>)<\/strong><\/p>\n}

<\/strong><\/p>\n

* M\u1ed7i gi\u00e2y \u0111\u1ed5i chi\u1ec1u 2f l\u1ea7n<\/p>\n

* N\u1ebfu cho d\u00f2ng \u0111i\u1ec7n qua b\u1ed9 ph\u1eadn l\u00e0m rung d\u00e2y trong hi\u1ec7n t\u01b0\u1ee3ng s\u00f3ng d\u1eebng th\u00ec d\u00e2y rung v\u1edbi t\u1ea7n s\u1ed1 2f<\/p>\n

3. C\u00f4ng th\u1ee9c t\u00ednh th\u1eddi gian \u0111\u00e8n hu\u1ef3nh quang s\u00e1ng trong m\u1ed9t chu k\u1ef3<\/strong><\/p>\n

Khi \u0111\u1eb7t \u0111i\u1ec7n \u00e1p\u00a0u<\/em>\u00a0= U_{0<\/sub>cos(\u03c9t + \u03c6u<\/sub>) v\u00e0o hai \u0111\u1ea7u b\u00f3ng \u0111\u00e8n, bi\u1ebft \u0111\u00e8n ch\u1ec9 s\u00e1ng l\u00ean khi \u00a0\u00a0\u2265 U1<\/sub>. G\u1ecdi\u00a0\u2206t l\u00e0 kho\u1ea3ng th\u1eddi gian \u0111\u00e8n s\u00e1ng trong m\u1ed9t chu k\u1ef3\u00a0\u00a0\u00a0V\u1edbi\u00a0(0 < \u2206\u03c6\u00a0< \u03c0\/2)<\/p>\n}

B.\u00c1p d\u1ee5ng :<\/strong><\/p>\n

B\u00e0i\u00a0 1<\/span><\/strong>\u00a0:\u00a0<\/strong>Bi\u1ec3u th\u1ee9c c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n xoay chi\u1ec1u ch\u1ea1y qua m\u1ed9t \u0111o\u1ea1n m\u1ea1ch l\u00e0\u00a0, v\u1edbi\u00a0I<\/em>_{0<\/sub>\u00a0> 0 v\u00e0\u00a0t<\/em>\u00a0t\u00ednh b\u1eb1ng gi\u00e2y (s). T\u00ednh t\u1eeb l\u00fac 0 s, x\u00e1c \u0111\u1ecbnh th\u1eddi \u0111i\u1ec3m \u0111\u1ea7u ti\u00ean m\u00e0 d\u00f2ng \u0111i\u1ec7n c\u00f3 c\u01b0\u1eddng \u0111\u1ed9 t\u1ee9c th\u1eddi b\u1eb1ng c\u01b0\u1eddng \u0111\u1ed9 hi\u1ec7u d\u1ee5ng ?<\/p>\n}

B\u00e0i\u00a0 gi\u1ea3i :<\/em><\/strong><\/p>\n

<\/em><\/strong><\/p>\n

Bi\u1ec3u th\u1ee9c c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n\u00a0\u00a0gi\u1ed1ng v\u1ec1 m\u1eb7t to\u00e1n h\u1ecdc v\u1edbi bi\u1ec3u th\u1ee9c li \u0111\u1ed9\u00a0\u00a0c\u1ee7a ch\u1ea5t \u0111i\u1ec3m dao \u0111\u1ed9ng c\u01a1 \u0111i\u1ec1u ho\u00e0. Do \u0111\u00f3, t\u00ednh t\u1eeb l\u00fac 0 s, t\u00ecm th\u1eddi \u0111i\u1ec3m \u0111\u1ea7u ti\u00ean \u0111\u1ec3 d\u00f2ng \u0111i\u1ec7n c\u00f3 c\u01b0\u1eddng \u0111\u1ed9 t\u1ee9c th\u1eddi b\u1eb1ng c\u01b0\u1eddng \u0111\u1ed9 hi\u1ec7u d\u1ee5ng\u00a0\u00a0 c\u0169ng gi\u1ed1ng nh\u01b0 t\u00ednh t\u1eeb l\u00fac 0 s, t\u00ecm th\u1eddi \u0111i\u1ec3m \u0111\u1ea7u ti\u00ean \u0111\u1ec3 ch\u1ea5t \u0111i\u1ec3m dao \u0111\u1ed9ng c\u01a1 \u0111i\u1ec1u ho\u00e0 c\u00f3 li \u0111\u1ed9\u00a0. V\u00ec pha ban \u0111\u1ea7u c\u1ee7a dao \u0111\u1ed9ng b\u1eb1ng 0, ngh\u0129a l\u00e0 l\u00fac 0 s th\u00ec ch\u1ea5t \u0111i\u1ec3m \u0111ang \u1edf v\u1ecb tr\u00ed gi\u1edbi h\u1ea1n\u00a0x\u00a0<\/em>=\u00a0A<\/em>, n\u00ean th\u1eddi \u0111i\u1ec3m c\u1ea7n t\u00ecm ch\u00ednh b\u1eb1ng th\u1eddi gian ng\u1eafn nh\u1ea5t \u0111\u1ec3 ch\u1ea5t \u0111i\u1ec3m \u0111i t\u1eeb v\u1ecb tr\u00ed gi\u1edbi h\u1ea1n\u00a0\u00a0x<\/em>\u00a0=\u00a0A\u00a0<\/em>\u0111\u1ebfn v\u1ecb tr\u00ed c\u00f3 li \u0111\u1ed9\u00a0. Ta s\u1eed d\u1ee5ng t\u00ednh ch\u1ea5t h\u00ecnh chi\u1ebfu c\u1ee7a m\u1ed9t ch\u1ea5t \u0111i\u1ec3m chuy\u1ec3n \u0111\u1ed9ng tr\u00f2n \u0111\u1ec1u l\u00ean m\u1ed9t \u0111\u01b0\u1eddng th\u1eb3ng n\u1eb1m trong m\u1eb7t ph\u1eb3ng qu\u1ef9 \u0111\u1ea1o l\u00e0 m\u1ed9t dao \u0111\u1ed9ng \u0111i\u1ec1u ho\u00e0 v\u1edbi c\u00f9ng chu k\u00ec \u0111\u1ec3 gi\u1ea3i B\u00e0i\u00a0 to\u00e1n n\u00e0y.<\/p>\n

Th\u1eddi gian ng\u1eafn nh\u1ea5t \u0111\u1ec3 ch\u1ea5t \u0111i\u1ec3m dao \u0111\u1ed9ng \u0111i\u1ec1u ho\u00e0 chuy\u1ec3n \u0111\u1ed9ng t\u1eeb v\u1ecb tr\u00ed c\u00f3 li \u0111\u1ed9\u00a0x<\/em>\u00a0=\u00a0A<\/em>\u00a0\u0111\u1ebfn v\u1ecb tr\u00ed c\u00f3 li \u0111\u1ed9\u00a0\u00a0 (t\u1eeb\u00a0P<\/em>\u00a0\u0111\u1ebfn\u00a0D<\/em>) ch\u00ednh b\u1eb1ng th\u1eddi gian ch\u1ea5t \u0111i\u1ec3m chuy\u1ec3n \u0111\u1ed9ng tr\u00f2n \u0111\u1ec1u v\u1edbi c\u00f9ng chu k\u00ec \u0111i t\u1eeb\u00a0P<\/em>\u00a0\u0111\u1ebfn\u00a0Q<\/em>\u00a0theo cung tr\u00f2n\u00a0PQ<\/em>.<\/p>\n

Tam gi\u00e1c\u00a0ODQ<\/em>\u00a0vu\u00f4ng t\u1ea1i\u00a0D\u00a0<\/em>v\u00e0 c\u00f3\u00a0OQ\u00a0<\/em>=\u00a0A<\/em>,\u00a0\u00a0n\u00ean ta c\u00f3 :\u00a0<\/p>\n

Suy ra :\u00a0 rad<\/p>\n

Th\u1eddi gian ch\u1ea5t \u0111i\u1ec3m chuy\u1ec3n \u0111\u1ed9ng tr\u00f2n \u0111\u1ec1u \u0111i t\u1eeb\u00a0P<\/em>\u00a0\u0111\u1ebfn\u00a0Q\u00a0<\/em>theo cung tr\u00f2n PQ l\u00e0 :\u00a0<\/p>\n

Trong bi\u1ec3u th\u1ee9c c\u1ee7a d\u00f2ng \u0111i\u1ec7n, th\u00ec t\u1ea7n s\u1ed1 g\u00f3c\u00a0\u03c9<\/em>\u00a0<\/em>= 100\u03c0\u00a0 rad\/s n\u00ean ta suy ra t\u00ednh t\u1eeb l\u00fac 0 s th\u00ec th\u1eddi \u0111i\u1ec3m \u0111\u1ea7u ti\u00ean m\u00e0 d\u00f2ng \u0111i\u1ec7n c\u00f3 c\u01b0\u1eddng \u0111\u1ed9 t\u1ee9c th\u1eddi b\u1eb1ng c\u01b0\u1eddng \u0111\u1ed9 hi\u1ec7u d\u1ee5ng l\u00e0 :<\/p>\n

<\/p>\n

B\u00e0i\u00a0 2 (B5-17<\/span><\/strong>SBT NC)<\/strong>M\u1ed9t \u0111\u00e8n n\u00eaon m\u1eafc v\u1edbi m\u1ea1ch \u0111i\u1ec7n xoay chi\u1ec1u c\u00f3 \u0111i\u1ec7n \u00e1p hi\u1ec7u d\u1ee5ng 220V v\u00e0 t\u1ea7n s\u1ed1 50Hz. Bi\u1ebft \u0111\u00e8n s\u00e1ng khi \u0111i\u1ec7n \u00e1p gi\u1eefa 2 c\u1ef1c kh\u00f4ng nh\u1ecf h\u01a1n 155V .<\/p>\n

a) Trong m\u1ed9t gi\u00e2y, bao nhi\u00eau l\u1ea7n \u0111\u00e8n s\u00e1ng? bao nhi\u00eau l\u1ea7n \u0111\u00e8n t\u1eaft ?<\/p>\n

b) T\u00ecnh t\u1ec9 s\u1ed1 gi\u1eefa th\u1eddi gian \u0111\u00e8n s\u00e1ng v\u00e0 th\u1eddi gian \u0111\u00e8n t\u1eaft trong m\u1ed9t chu k\u1ef3 c\u1ee7a d\u00f2ng \u0111i\u1ec7n ?<\/p>\n

H\u01b0\u1edbng d\u1eabn<\/span><\/strong>\u00a0:<\/strong><\/p>\n

<\/strong><\/p>\n

a) \u00a0<\/p>\n

-Trong m\u1ed9t chu k\u1ef3 c\u00f3 2 kho\u1ea3ng th\u1eddi gian th\u1ecfa m\u00e3n \u0111i\u1ec1u ki\u1ec7n \u0111\u00e8n s\u00e1ng\u00a0\u00a0 Do \u0111\u00f3 trong m\u1ed9t chu k\u1ef3 ,\u0111\u00e8n ch\u1edbp s\u00e1ng 2 l\u1ea7n ,2 l\u1ea7n \u0111\u00e8n t\u1eaft<\/p>\n

-S\u1ed1 chu k\u1ef3 trong m\u1ed9t gi\u00e2y : n = f = 50 chu k\u1ef3<\/p>\n

-Trong m\u1ed9t gi\u00e2y \u0111\u00e8n ch\u1edbp s\u00e1ng 100 l\u1ea7n , \u0111\u00e8n ch\u1edbp t\u1eaft 100 l\u1ea7n<\/p>\n

b)T\u00ecm kho\u1ea3ng th\u1eddi gian \u0111\u00e8n s\u00e1ng trong n\u1eeda chu k\u1ef3 \u0111\u1ea7u<\/p>\n

\u00a0<\/p>\n

-Th\u1eddi gian \u0111\u00e8n s\u00e1ng trong n\u1eeda chu k\u1ef3 : \u00a0<\/p>\n

Th\u1eddi gian \u0111\u00e8n s\u00e1ng trong m\u1ed9t chu k\u1ef3 :\u00a0<\/p>\n

-Th\u1eddi gian \u0111\u00e8n t\u1eaft trong chu k\u1ef3\u00a0:\u00a0
\n<\/strong><\/p>\n

-T\u1ec9 s\u1ed1 th\u1eddi gian \u0111\u00e8n s\u00e1ng v\u00e0 th\u1eddi gian \u0111\u00e8n t\u1eaft trong m\u1ed9t chu k\u1ef3 :\u00a0\u00a0<\/p>\n

C\u00f3 th\u1ec3 gi\u1ea3i B\u00e0i\u00a0 to\u00e1n tr\u00ean\u00a0 b\u1eb1ng\u00a0pp n\u00eau tr\u00ean<\/strong>\u00a0:<\/p>\n

\u00a0\u00a0. V\u1eady th\u1eddi gian \u0111\u00e8n s\u00e1ng t\u01b0\u01a1ng \u1ee9ng chuy\u1ec3n \u0111\u1ed9ng tr\u00f2n \u0111\u1ec1u quay g\u00f3c\u00a0\u00a0v\u00e0 g\u00f3c\u00a0\u00a0 \u00a0. Bi\u1ec5u di\u1ec5n b\u1eb1ng h\u00ecnh ta th\u1ea5y t\u1ed5ng th\u1eddi gian \u0111\u00e8n s\u00e1ng \u1ee9ng v\u1edbi th\u1eddi gian t_{S<\/sub>=4.t v\u1edbi t l\u00e0 th\u1eddi gian b\u00e1n k\u00ednh qu\u00e9t\u00a0 g\u00f3c\u00a0\u00a0\u00a0; v\u1edbi\u00a0.<\/p>\n}

\u00c1p d\u1ee5ng : \u00a0<\/p>\n

B\u00e0i\u00a0 3<\/span>( \u0110H10-11):<\/strong>\u00a0T\u1ea1i th\u1eddi \u0111i\u1ec3m t, \u0111i\u1ec7n \u00e1p\u00a0\u00a0(trong \u0111\u00f3 u t\u00ednh b\u1eb1ng V, t t\u00ednh b\u1eb1ng s) c\u00f3 gi\u00e1 tr\u1ecb\u00a0\u00a0 v\u00e0 \u0111ang gi\u1ea3m. Sau th\u1eddi \u0111i\u1ec3m \u0111\u00f3 1\/300 (s), \u0111i\u1ec7n \u00e1p n\u00e0y c\u00f3 gi\u00e1 tr\u1ecb l\u00e0<\/p>\n

A. -100V. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0B.\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0C<\/span>. –\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0D. 200 V.<\/p>\n

HD gi\u1ea3i\u00a0<\/span><\/strong>:<\/p>\n

<\/p>\n

D\u00f9ng m\u1ed1i li\u00ean quan gi\u1eefa dddh v\u00e0 CDTD , khi t=0 , u \u1ee9ng v\u1edbi CDTD \u1edf C . V\u00e0o th\u1eddi \u0111i\u1ec3m t , u=\u00a0\u00a0v\u00e0 \u0111ang gi\u1ea3m n\u00ean \u1ee9ng v\u1edbi CDTD t\u1ea1i M v\u1edbi\u00a0\u00a0.Ta c\u00f3 :\u00a0<\/p>\n

Suy ra\u00a0\u00a0. V\u00ec v\u1eady th\u00eam \u00a0\u00a0<\/p>\n

\u1ee9ng v\u1edbi CDTD \u1edf B v\u1edbi\u00a0<\/p>\n

Suy ra l\u00fac \u0111\u00f3 u= –\u00a0<\/p>\n

B\u00e0i\u00a0<\/span>\u00a05:<\/strong>\u00a0V\u00e0o c\u00f9ng m\u1ed9t th\u1eddi \u0111i\u1ec3m n\u00e0o \u0111\u00f3, hai d\u00f2ng \u0111i\u1ec7n xoay<\/p>\n

chi\u1ec1u i_{1<\/sub>\u00a0= Io<\/sub>cos(\u03c9t + \u03c61<\/sub>) v\u00e0 i2<\/sub>\u00a0= Io<\/sub>cos(\u03c9t + \u03c62<\/sub>) \u0111\u1ec1u c\u00f9ng c\u00f3 gi\u00e1<\/p>\n}

tr\u1ecb t\u1ee9c th\u1eddi l\u00e0 0,5I_{o<\/sub>, nh\u01b0ng m\u1ed9t d\u00f2ng \u0111i\u1ec7n \u0111ang gi\u1ea3m,<\/p>\n}

c\u00f2n m\u1ed9t d\u00f2ng \u0111i\u1ec7n \u0111ang t\u0103ng. Hai d\u00f2ng \u0111i\u1ec7n n\u00e0y l\u1ec7ch pha<\/p>\n

nhau m\u1ed9t g\u00f3c b\u1eb1ng.<\/p>\n

\u00a0 A.\u00a0<\/strong>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0B<\/span>.\u00a0<\/strong>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0C. \u00a0<\/strong>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0D.\u00a0<\/strong><\/strong><\/p>\n

H\u01b0\u1edbng d\u1eabn gi\u1ea3i:<\/strong>D\u00f9ng m\u1ed1i li\u00ean quan gi\u1eefa dddh v\u00e0 chuy\u1ec3n \u0111\u1ed9ng tr\u00f2n \u0111\u1ec1u :<\/p>\n

<\/p>\n

\u0110\u1ed1i v\u1edbi d\u00f2ng i_{1<\/sub>\u00a0khi c\u00f3 gi\u00e1 tr\u1ecb t\u1ee9c th\u1eddi 0,5I0<\/sub>\u00a0v\u00e0 \u0111\u0103ng t\u0103ng \u1ee9ng v\u1edbi chuy\u1ec3n \u0111\u1ed9ng tr\u00f2n \u0111\u1ec1u \u1edf M\u2019 , c\u00f2n \u0111\u1ed1i v\u1edbi d\u00f2ng i2<\/sub>\u00a0khi c\u00f3 gi\u00e1 tr\u1ecb t\u1ee9c th\u1eddi 0,5I0<\/sub>\u00a0v\u00e0 \u0111\u0103ng gi\u1ea3m \u1ee9ng v\u1edbi chuy\u1ec3n \u0111\u1ed9ng tr\u00f2n \u0111\u1ec1u \u1edf M\u00a0 B\u1eb1ng c\u00f4ng th\u1ee9c l\u01b0\u1ee3ng gi\u00e1c \u1edf ch\u01b0\u01a1ng dd c\u01a1 , ta c\u00f3 :\u00a0suy ra 2 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n t\u1ee9c th\u1eddi i1<\/sub>\u00a0v\u00e0 i2<\/sub>\u00a0l\u1ec7ch pha nhau\u00a0<\/strong><\/p>\n}

C: B\u00c0I T\u1eacP<\/strong><\/p>\n

B\u00e0i 1<\/strong>\u00a0D\u00f2ng \u0111i\u1ec7n xoay chi\u1ec1u qua m\u1ed9t \u0111o\u1ea1n m\u1ea1ch c\u00f3 bi\u1ec3u th\u1ee9c\u00a0. Th\u1eddi \u0111i\u1ec3m th\u1ee9 2009 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n t\u1ee9c th\u1eddi b\u1eb1ng c\u01b0\u1eddng \u0111\u1ed9 hi\u1ec7u d\u1ee5ng l\u00e0:<\/p>\n

A.\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0B.\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 C.\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0D. \u0110\u00e1p \u00e1n kh\u00e1c<\/p>\n

B\u00e0i 2<\/strong>\u00a0(\u0110\u1ec1 23 c\u1ee5c kh\u1ea3o th\u00ed ) \u0110i\u1ec7n \u00e1p t\u1ee9c th\u1eddi gi\u1eefa hai \u0111\u1ea7u \u0111o\u1ea1n m\u1ea1ch\u00a0\u00a0. Th\u1eddi \u0111i\u1ec3m g\u1ea7n nh\u1ea5t sau \u0111\u00f3 \u0111\u1ec3 \u0111i\u1ec7n \u00e1p t\u1ee9c th\u1eddi \u0111\u1ea1t gi\u00e1 tr\u1ecb 120V l\u00e0 :<\/p>\n

A.1\/600s \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0B.1\/100s \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 C.0,02s \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0D.1\/300s<\/p>\n

B\u00e0i 3:<\/strong>\u00a0D\u00f2ng \u0111i\u1ec7n xoay chi\u1ec1u ch\u1ea1y qua m\u1ed9t \u0111o\u1ea1n m\u1ea1ch c\u00f3 bi\u1ec3u th\u1ee9c\u00a0, \u00a0t\u00ednh b\u1eb1ng gi\u00e2y (s). D\u00f2ng \u0111i\u1ec7n c\u00f3 c\u01b0\u1eddng \u0111\u1ed9 t\u1ee9c th\u1eddi b\u1eb1ng kh\u00f4ng l\u1ea7n th\u1ee9 ba v\u00e0o th\u1eddi \u0111i\u1ec3m<\/p>\n

A.. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0B.. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0C.. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 D..<\/p>\n

C\u00e2u4.<\/strong>\u00a0M\u1ed9t chi\u1ebfc \u0111\u00e8n n\u00ea\u00f4n \u0111\u1eb7t d\u01b0\u1edbi m\u1ed9t \u0111i\u1ec7n \u00e1p xoay chi\u1ec1u 119V \u2013 50Hz. N\u00f3 ch\u1ec9 s\u00e1ng l\u00ean khi \u0111i\u1ec7n \u00e1p t\u1ee9c th\u1eddi gi\u1eefa hai \u0111\u1ea7u b\u00f3ng \u0111\u00e8n l\u1edbn h\u01a1n 84V. Th\u1eddi gian b\u00f3ng \u0111\u00e8n s\u00e1ng trong m\u1ed9t chu k\u1ef3 l\u00e0 bao nhi\u00eau?<\/p>\n

A. \u2206t = 0,0100s. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0B. \u2206t = 0,0133s. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0C. \u2206t = 0,0200s. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0D. \u2206t = 0,0233s.<\/p>\n

B\u00e0i 5<\/strong>\u00a0(\u0110H2007)D\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua m\u1ed9t \u0111o\u1ea1n m\u1ea1ch c\u00f3 bi\u1ec3u th\u1ee9c i = I_{0<\/sub>cos100\u03c0t. Trong kho\u1ea3ng th\u1eddi gian t\u1eeb 0 \u0111\u1ebfn 0,01s c\u01b0\u1eddng \u0111\u1ed9 d\u0111 t\u1ee9c th\u1eddi c\u00f3 gi\u00e1 tr\u1ecb b\u1eb1ng 0,5I0<\/sub>\u00a0v\u00e0o nh\u1eefng th\u1eddi \u0111i\u1ec3m<\/p>\n}

A.\u00a0\u00a0s\u00a0 v\u00e0\u00a0s\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0B.\u00a0s\u00a0 v\u00e0 \u00a0\u00a0s<\/p>\n

C.\u00a0s\u00a0 v\u00e0\u00a0s\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0D.\u00a0s\u00a0 v\u00e0\u00a0s.<\/p>\n

B\u00e0i 6<\/strong>\u00a0D\u00f2ng \u0111i\u1ec7n xoay chi\u1ec1u qua m\u1ed9t \u0111o\u1ea1n m\u1ea1ch c\u00f3 bi\u1ec3u th\u1ee9c\u00a0\u00a0. Th\u1eddi \u0111i\u1ec3m th\u1ee9 2009 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n t\u1ee9c th\u1eddi b\u1eb1ng c\u01b0\u1eddng \u0111\u1ed9 hi\u1ec7u d\u1ee5ng l\u00e0:<\/p>\n

A.\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 B.\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 C.\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 D. \u0110\u00e1p \u00e1n kh\u00e1c<\/p>\n

B\u00e0i 7<\/strong>\u00a0\u0110\u1eb7t \u0111i\u1ec7n \u00e1p xoay chi\u1ec1u c\u00f3 tr\u1ecb hi\u1ec7u d\u1ee5ng U=120V t\u1ea7n s\u1ed1 f=60Hz v\u00e0o hai \u0111\u1ea7u m\u1ed9t b\u00f3ng \u0111\u00e8n hu\u1ef3nh quang. Bi\u1ebft \u0111\u00e8n ch\u1ec9 s\u00e1ng l\u00ean khi \u0111i\u1ec7n \u00e1p \u0111\u1eb7t v\u00e0o \u0111\u00e8n kh\u00f4ng nh\u1ecf h\u01a1n 60V. Th\u1eddi gian \u0111\u00e8n s\u00e1ng trong m\u1ed7i gi\u00e2y l\u00e0:<\/p>\n

A.\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0B. \u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0C .\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0D.<\/p>\n

B\u00e0i 8<\/strong>\u00a0\u0110i\u1ec7n \u00e1p gi\u1eefa hai \u0111\u1ea7u m\u1ed9t \u0111o\u1ea1n m\u1ea1ch c\u00f3 bi\u1ec3u th\u1ee9c \u00a0. Nh\u1eefng th\u1eddi \u0111i\u1ec3m t n\u00e0o sau \u0111\u00e2y \u0111i\u1ec7n \u00e1p t\u1ee9c th\u1eddi\u00a0:<\/p>\n

A.\u00a0s\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 B.\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0C.\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0D.<\/p>\n

B\u00e0i 9<\/strong>\u00a0\u0110\u1eb7t \u0111i\u1ec7n \u00e1p xoay chi\u1ec1u c\u00f3 tr\u1ecb hi\u1ec7u d\u1ee5ng U=120V t\u1ea7n s\u1ed1 f=60Hz v\u00e0o hai \u0111\u1ea7u m\u1ed9t b\u00f3ng \u0111\u00e8n hu\u1ef3nh quang. Bi\u1ebft \u0111\u00e8n ch\u1ec9 s\u00e1ng l\u00ean khi \u0111i\u1ec7n \u00e1p \u0111\u1eb7t v\u00e0o \u0111\u00e8n kh\u00f4ng nh\u1ecf h\u01a1n 60V. T\u1ec9 s\u1ed1 th\u1eddi gian \u0111\u00e8n s\u00e1ng v\u00e0 \u0111\u00e8n t\u1eaft trong 30 ph\u00fat l\u00e0:<\/p>\n

A. 2 l\u1ea7n \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 B. 0,5 l\u1ea7n \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0C. 3 l\u1ea7n \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 D. 1\/3 l\u1ea7n<\/p>\n

B\u00e0i\u00a0<\/strong>10<\/strong>\u00a0D\u00f2ng \u0111i\u1ec7n \u00a0ch\u1ea1y qua m\u1ed9t \u0111o\u1ea1n m\u1ea1ch c\u00f3 bi\u1ec3u th\u1ee9c i = I_{0<\/sub>cos100\u03c0t. Trong m\u1ed7i n\u1eeda chu k\u1ef3, khi d\u00f2ng \u0111i\u1ec7n ch\u01b0a \u0111\u1ed5i chi\u1ec1u th\u00ec\u00a0 kho\u1ea3ng th\u1eddi gian \u0111\u1ec3 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n t\u1ee9c th\u1eddi c\u00f3 gi\u00e1 tr\u1ecb\u00a0 tuy\u1ec7t \u0111\u1ed1i l\u1edbn h\u01a1n ho\u1eb7c b\u1eb1ng 0,5I0\u00a0\u00a0<\/sub>l\u00e0<\/p>\n}

A. \u00a01\/300 s \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0B. 2\/300 s \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 C. 1\/600 s \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0D 5\/600s<\/p>\n

Ph\u1ea7n 2: C\u00e1c b\u1ea1n xem ti\u1ebfp \u1edf d\u01b0\u1edbi \u0111\u00e2y:<\/strong><\/h3>\n