Question 247: AC fundamentals

Question

The phase difference between the alternating current and $$emf$$ is $${\pi  \over 2}.$$ Which of the following cannot be the constituent of the circuit?

Accepted Answer

The phase difference between the alternating current and emf in an AC circuit depends on the components in the circuit:
In a purely resistive ($R$) circuit, the current and emf are in phase, meaning the phase difference is $0$.
In a purely inductive ($L$) circuit, the current lags behind the emf by $\frac{\pi}{2}$, meaning the phase difference is $\frac{\pi}{2}$.
In a purely capacitive ($C$) circuit, the current leads the emf by $\frac{\pi}{2}$, again meaning the phase difference is $\frac{\pi}{2}$.
In an $L$-$R$ or $L$-$C$ circuit, the phase difference depends on the relative values of $L$, $R$, and $C$ and can be anywhere between $0$ and $\frac{\pi}{2}$.
Therefore, if the phase difference between the alternating current and emf is $\frac{\pi}{2}$, then the circuit cannot contain only a resistor ($R$) since that would give a phase difference of $0$. So, the answer is Option A: $R,L$. The phase difference would not be $\frac{\pi}{2}$ if the circuit contains both a resistor and an inductor.

Answer

$$R,L$$

Answer

$$C$$ alone

Answer

$$L$$ alone

Answer

$$L, C$$

AC fundamentals

The phase difference between the alternating current and $emf is {\pi \over 2}.$ Which of the following cannot be the constituent of the circuit?

Choose the correct answer: