如图7－9所示，一正圆台形导体,两个端面的半径分别为a和b,长度为L。恒定电流I均匀地流过导体的任

A .https://assets.asklib.com/psource/2015110110082091205.jpg B .https://assets.asklib.com/psource/2015110110083756430.jpg C .https://assets.asklib.com/psource/2015110110085337283.jpg D .https://assets.asklib.com/psource/201511011009061961.jpg

A . 2.5A和1.5A B . 1A和0A C . 2.5A和0A D . 1A和1.5A

A .https://assets.asklib.com/psource/52051448008013347.png B .https://assets.asklib.com/psource/18601448008023203.png C .https://assets.asklib.com/psource/31541448008033900.png D .https://assets.asklib.com/psource/40921448008043530.png

A . Q=-F，M=-Fl B . Q=F，M=Fl C . Q=-F，M=Fl D . Q=F，M=-Fl

A . 4R，2πR B . 4R，-2πR C . -4R，2πR D . -4R，-2πR

<img src='https://img2.soutiyun.com/ask/uploadfile/9090001-9093000/ba8bf5913a6bf998.jpg' /> A．σ1=-σ， σ2=+σ B．<img src='https://img2.soutiyun.com/ask/uploadfile/9090001-9093000/3cc7b22c06f96c98.jpg' /> C．σ1=-σ，σ2=0 D．<img src='https://img2.soutiyun.com/ask/uploadfile/9090001-9093000/fb7873e64af98a98.jpg' />

如图7-52所示,两个半径为R的相同的金属环在a 、b两点接触(ab连线为环直径)，并相互垂直故置。电流I沿ab连线方向由a端流入,b端流出,则环中心O点的磁感应强度大小为()。 <img src='https://img2.soutiyun.com/ask/2020-05-09/95788388343784.png' /> A.0 <img src='https://img2.soutiyun.com/ask/2020-05-09/957883663105296.png' />

<img src='https://img2.soutiyun.com/ask/2020-06-04/960130303965218.jpg' />

因柱形电容器内、外导体截面半径分别为R₁和R₂(R₁＜R₂),中间充满介电常数为ε的电介质.当两极板间的电压随时间的变化<img src='https://img2.soutiyun.com/ask/2020-12-29/978082344279563.png' />时(k为常数)，求介质内距圆柱轴线为r处的位移电流密度.

<img src='https://img2.soutiyun.com/ask/2020-07-20/964084761145914.png' />

如图4-18所示，两物体质量分别为m1和m2,定滑轮的质量为m,半径为r,可视作均匀圆盘。已知m2与桌面间的滑动摩擦系数为μk,试求m1下落的加速度和两段绳子中的张力各是多少。设绳子和滑轮间无相对滑动,滑轮轴受到的摩擦力可忽略不计。 <img src='https://img2.soutiyun.com/ask/2020-04-30/957088583674837.png' />

<img src='https://img2.soutiyun.com/ask/2020-04-07/955116604116982.jpg' />

<img src='https://img2.soutiyun.com/ask/2020-07-01/962459710924663.png' />

由下式给出：<img src='https://img2.soutiyun.com/ask/2020-07-14/963589443855635.png' />。 分析:应用安培环路定理求解。注意环路中电流的计算，应该是先求出载流导体内电流密度，再求出穿过环路的电流。 <img src='https://img2.soutiyun.com/ask/2020-07-14/963589465464871.png' />

<img src='https://img2.soutiyun.com/ask/uploadfile/10797001-10800000/624b09436cf223071c776c62ac71eec9.png' /> A.RA=tan30°P，RB=1/tan30°P B.RA=1/tan30°P，RB=tan30°P C.RA=sin30°P，RB=cos30°P D.RA=cos30°P，RB=sin30°P

A．若仅把Frame1的Enabled属性设为False，则op1、op2仍可用 B．对于上图，op1.Value自值为True C．对于上图，执行op1.Value＝False命令，则“往返”单选按钮被选中 D．对于上图，执行op1.Value＝0命令，程序出错

<img src='https://img2.soutiyun.com/ask/2020-07-16/963764961197678.png' />

<img src='https://img2.soutiyun.com/ask/2020-04-21/956307090164021.png' />

如图5-38所示，一锥顶角为<img src='https://img2.soutiyun.com/ask/2020-04-30/957108379267003.png' />的圆台,上下底面半径分别为r和R ,在它的侧面上均匀带电，电荷面密度为σ,求顶点O的电势。(以无穷远处为电势零点) <img src='https://img2.soutiyun.com/ask/2020-04-30/95710839144979.png' />

某二进制数字基带传输系统如图9-26所示。图中(an)与an'分别为发送的数字序列和恢复的数字序列，已知发送滤波器的传输函数为 <img src='https://img2.soutiyun.com/ask/2020-08-31/967753022168753.png' /> 信道传输函数C(w)=1, n(t)是双边功率谱密度为m/2(W/Hz)的高斯白噪声。 <img src='https://img2.soutiyun.com/ask/2020-08-31/967753044076006.png' /> (1)若要使该系统最佳化,试问G_r(w)应如何选择？ (2)该系统无码间干扰的最高码元传输速率为多少？ (3)若发送的二进制基带信号为双极性信号，接收信号码元能量为E.并且P(0) = P(1) .试推导该系统的最佳判决限和最小误码率。

<img src='https://img2.soutiyun.com/ask/2020-07-22/964281249714169.png' /> A、<img src='https://img2.soutiyun.com/ask/2020-07-22/96428126108882.png' /> B、<img src='https://img2.soutiyun.com/ask/2020-07-22/96428127157442.png' /> C、<img src='https://img2.soutiyun.com/ask/2020-07-22/964281285841236.png' /> D、<img src='https://img2.soutiyun.com/ask/2020-07-22/964281300748088.png' />

<img src='https://img2.soutiyun.com/ask/2021-02-09/981718618897701.png' />