如图5－30所示,AB为一根长为2L的带电细棒,左半部均匀带有负电荷一q,右半部均匀带有正电荷q.

A . A B . B C . C D . D

A . A B . B C . C D . D

A . （1／12）ml ω B . （7／24）ml ω C . （7／48）ml ω D . （7／96）ml ω

A .https://assets.asklib.com/psource/2015103013245572474.jpg B .https://assets.asklib.com/psource/2015103013251189703.jpg C .https://assets.asklib.com/psource/201510301325278240.jpg D .https://assets.asklib.com/psource/2015103013253943153.jpg

A . A B . B C . C D . D

A .https://assets.asklib.com/psource/2015103014503984624.jpg B .https://assets.asklib.com/psource/2015103014505084240.jpg C .https://assets.asklib.com/psource/2015103014510485319.jpg D .https://assets.asklib.com/psource/2015103014512148828.jpg

A . ['['0B .https://assets.asklib.com/psource/201510301459596729.jpg C .https://assets.asklib.com/psource/2015103015000973770.jpg D .https://assets.asklib.com/psource/2015103015001942512.jpg

<img src='https://img2.soutiyun.com/ask/uploadfile/5088001-5091000/0a17aa9b2811a784c73e007ea80e7b60.jpg' /> A．<img src='https://img2.soutiyun.com/shangxueba/ask/5088001-5091000/5089780/onerrorimg.jpg' /> B．<img src='https://img2.soutiyun.com/shangxueba/ask/5088001-5091000/5089780/onerrorimg.jpg' /> C．<img src='https://img2.soutiyun.com/shangxueba/ask/5088001-5091000/5089780/onerrorimg.jpg' /> D．<img src='https://img2.soutiyun.com/shangxueba/ask/5088001-5091000/5089780/onerrorimg.jpg' />

<img src='https://img2.soutiyun.com/ask/uploadfile/9663001-9666000/40ddb3c2258dc66deb5161b613ce1e75.png' />

<img src='https://img2.soutiyun.com/shangxueba/ask/18627001-18630000/18627235/2016071917373619874.jpg' /><img src='https://img2.soutiyun.com/shangxueba/ask/18627001-18630000/18627235/201607191737384184.jpg' /> A．A B． B C． C D． D

<img src='https://img2.soutiyun.com/ask/2020-07-08/963065823078817.png' />

A.0 B.39／(4L) C.39／(2L) D.69／L

(1)0点的磁感应强度; (2)转动导线的磁矩 <img src='https://img2.soutiyun.com/ask/2020-07-09/963136781771038.png' />

如题4-37图所示，一长为<img src='https://img2.soutiyun.com/ask/2020-11-19/974670601200382.png' />、质量为m的均匀细棒，在光滑的平面上绕质心作无滑动的转动，其角速度为ω。若棒突然改绕其一端转动，求：(1)以端点为转轴的角速度ω';(2)在此过程中转动动能的改变。 <img src='https://img2.soutiyun.com/ask/2020-11-19/974670608244785.png' />

<img src='https://img2.soutiyun.com/shangxueba/ask/50259001-50262000/50261019/963137010554123.png' />

如图所示，一直流电源(电压为U0，内阻为零)经一集中参数电阻R合闸于AB长线上。AB长为l，波阻抗为Z，波在其上传播速度为υ。B点开路，C为AB上一点，且以K合闸时刻为τ=0，试绘出R=Z时，uc(t)的波形。 <img src='https://img2.soutiyun.com/ask/2019-10-24/940761872902012.png' />

A．0 B．3g/4L C．3g/2L D．6g/L

如图2-4所示的电缆<img src='https://img2.soutiyun.com/ask/2020-08-06/965554530907066.png' />的长为s，跨度为2l，电缆的最低点0与杆顶连线AB的距离为f，则电缆长可按下面公式计算： <img src='https://img2.soutiyun.com/ask/2020-08-06/96555455143324.png' /> <img src='https://img2.soutiyun.com/ask/2020-08-06/965554618117054.png' /> 当f变化了Δf时，电缆长的变化约为多少？

A．合外力矩从大到小，角速度从小到大，角加速度从大到小 B．合外力矩从大到小，角速度从小到大，角加速度从小到大 C．合外力矩从大到小，角速度从大到小，角加速度从大到小 D．合外力矩从大到小，角速度从大到小，角加速度从小到大

A．<img src='https://img2.soutiyun.com/shangxueba/ask/17043001-17046000/17045377/92c5108-chaoxing2016-752539.jpeg' /> B．<img src='https://img2.soutiyun.com/shangxueba/ask/17043001-17046000/17045377/ad76744-chaoxing2016-752540.jpeg' /> C．<img src='https://img2.soutiyun.com/shangxueba/ask/17043001-17046000/17045377/f296834-chaoxing2016-752541.jpeg' /> D．<img src='https://img2.soutiyun.com/shangxueba/ask/17043001-17046000/17045377/0b30476-chaoxing2016-752542.jpeg' />