Question

An A.C voltage $V=5 \cos (1000\, t ) V$ is applied to a L-R series circuit of inductance $3 \,mH$ and resistance $4 \,\Omega$. The value of maximum current in the circuit is _____ $A$.

• A. $0.8$
• B. $1.0$
• C. $\frac{5}{7}$
• D. $\frac{5}{\sqrt{7}}$

Answer 1

Answer: (B)

$V =5 \cos 1000 t$ volt
$V=V_{0} \cos \omega t$
$V_{0}=5\, volt $
$ \omega=1000 \,rad / s$
$L=3 \times 10^{-3} H, R=4\, \Omega$
Maximum current $10=\frac{ V _{0}}{Z}$,
$10=\frac{5}{\sqrt{\omega^{2} L^{2}+R^{2}}}=\frac{5}{5}=1 A$