Q 7.13 (b) A coil of inductance 0.50Hand resistance 100\Omega is connected to a 200V50Hz  ac supply. What is the time lag between the voltage maximum and the current maximum?

Answers (1)
P Pankaj Sanodiya

Let the voltage  in the circuit be 

V = V_0coswt and 

Current in the circuit be 

I = I_0cos(wt-\phi )

Where \phi is the phase difference between voltage and current.

 V is maximum At

t = 0

I is maximum At 

  t=\frac{w}{\phi } 

Hence, the time lag between voltage maximum and the current maximum is

 \frac{w}{\phi }.

For phase difference \phi  we have 

tan\phi =\frac{wL}{R}=\frac{2\pi *50*0.5}{100}=1.57

\phi =57.5^0

t=\frac{\phi}{w}=\frac{57.5*\pi}{180*2\pi *50}=3.2ms

Hence time lag between the maximum voltage and the maximum current is 3.2ms