Question

ii) In a purely resistive ac circuit, the current ......
A) leads the emf by ft rad
B) leads the emf by rad
C) and emfare in phase
D) lags the emf by "rad
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Answer 1

Answer:

In purely resistive circuit , the current is in phase with emf option ( C)

Explanation:

Given as :

The condition for a purely resistive AC circuit :

When current flowing through pure resistance circuit , no back emf is set up . Applied voltage has to overcome the i.R drop only .

i.e i.R = v

or, i = $\dfrac{v}{R}$

Or, i = $\dfrac{v_m_a_x sinwt}{R}$

Current will be maximum for wt = 90°

So, i = $\dfrac{v_m_a_x}{R}$

instantaneous current can be expressed as

i = $I_m_a_x$ sin wt

From the expression of instantaneous applied voltage and instantaneous current, it is clear that in a pure resistive circuit , the applied voltage and current are in phase with each other .

Hence, In purely resistive circuit , the current is in phase with emf ( C) . Answer