Question

When the switch $S$ is closed at $t=0$, identify the correct statement just after closing the switch as shown in figure :

• A. The current in the circuit is maximum
• B. Equal and opposite voltages are dropped across inductor and resistor
• C. The entire voltage is dropped across inductor
• D. All of the above

Answer 1

Answer: (C)

The entire voltage is dropped across inductor

The equation of Voltage across them is
$L\frac{di}{dt}+\frac{i}{C}dt-iR=V$ --------------(1)
$li{m}_{t\to 0}(L\frac{di}{dt}+\frac{i}{C}dt-iR)=V$
at t=0, if $i=finite$,
then $\frac{di}{dt}=\infty$
Hence $t\to 0,i\to 0$
$L\frac{di}{dt}=0$
All the voltage drop happens across the inductor