Which of the following best describes a physiological difference between the contraction of smooth muscle compared with the contraction of cardiac muscle and skeletal muscle?( )
A. Ca++ independent
B. Does not require an action potential
C. Requires more energy
D. Shorter in duration
E. None of the above
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在直流电路中,电感相当于______ ,电容相当于______ 。 ______
一个6条支路4个节点的电路,可列写的相互独立的KVL方程个数是______ ______ ______ 。
两正弦信号i1=200cos(100t+30○)和i2=200cos(100t-15○)的相位差是( )。
A. i1超前i245○
B. i1滞后i245○
C. i1超前i2135○
D. 无法判断
电源的内阻抗1+j3Ω,若所接负载可变,则负载阻抗应取( )时,可获得最大功率。
A. 1+j3Ω
B. –1–j3Ω
C. –1+j3Ω
D. 1–j3Ω
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