1. For an inductor, should the voltage be out of phase with the current? By how

Question

1. For an inductor, should the voltage be out of phase with the current? By how much? Why?

2. For a capacitor, should the voltage be out of the phase with the current? By how much? Why?

3.How did the phase constant change as the frequency increases in a RL circuit? Why?

4. How did the phase constant as the frequency increase in a RC circuit? Why?

5. How did the phase constant change as the ferquency increases in a RLC ciurcut? Why?

6. What is the phase constant when the RLC circuit is at resonance? why?

Explanation / Answer

1. For an inductor, should the voltage be out of phase with the current? By how much? Why?

The voltage must be 90 degree out of phase for inductor .It is explained as follows

XL=jwL

V=I*XL=jwLI=>V/I=jwL so seen clearly j means 90 degree out of phase

The reason is that current across inductor is not changed instantaneously so it lags behind voltage by 90 degree.

2. For a capacitor, should the voltage be out of the phase with the current? By how much? Why?

Answer->

The voltage must be 90 degree out of phase for capacitor.It is explained as follows

XC=1/jwC

V=I*XL=1/jwCI=>V/I=1/jwC so seen clearly j means 90 degree out of phase

The reason is that voltage across capacitor is not changed instantaneously so it lags behind current by 90 degree.

.3.How did the phase constant change as the frequency increases in a RL circuit? Why?

for RL

phase angle=tan^(-)(wL/R) so as frequency increases ,the phase angle increases

4. How did the phase constant as the frequency increase in a RC circuit? Why?

answer=>phase angle=tan^(-)(1/wCR) so as frequency increases ,the phase angle decreases

5.How did the phase constant change as the ferquency increases in a RLC ciurcut? Why?

ANswer=>phase angle=tan^(-1)((wL-1/wC)/R)

At higher frequency the circuit will be inductive while at lower frequency circuit will be capacitive magnitude of phase angle increases sometimes and decreases sometime with increase in frequency but considering signed value of phase angle it increases with increase in frequency

6.What is the phase constant when the RLC circuit is at resonance? why?

answer => 0 because phase angle=tan^(-1)((wL-1/wC)/R) and at resonance wL=1/wC so phase angle is 0.

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