Question

In an $AC$ series circuit, the instantaneous current is $zero$ when the instantaneous voltage is maximum. Connected to the source may be a

• A. Pure inductor
• B. Pure capacitor
• C. Pure resistor
• D. combination of an inductor and a capacitor

Answer 1

Answer: (A), (B), (D)

combination of an inductor and a capacitor

In an AC series circuit, passive components which can be connected are resistor, inductor and capacitor.

$\text{Resistors:}$ Resistors are used to reduce current flow, adjust signal level, divide voltages, etc. They don’t have any sort of storage ability. Resistors obey ohm's law. According to ohm's law voltage is directly proportional to the current flowing in the circuit when all physical conditions, like temperature, remain constant.

So, here, we can conclude that there is no phase difference in voltage and current when the resistor is connected to in an $\text{AC}$ series circuit.

$\therefore$ Phase difference, $\Delta \varphi =0$

$\text{Inductor}:$ It has an ability to store energy in a magnetic field when connected to an energy source. Inductors also oppose the flow of current.

In case of pure inductive circuit voltage leads current by $\frac{\pi }{2}$.

$\text{Capacitor:}$ Capacitor is also a two terminal passive element which can store energy.
In case of pure capacitive circuit, current lags voltage by $\frac{\pi }{2}$.

In an $AC$ series circuit, the instantaneous current is $zero$ when the instantaneous voltage is maximum, this will happen only if the phase difference between the current and the voltage is $\frac{\pi }{2}$.

The combination of inductor and capacitor also produce a phase difference of $\frac{\pi }{2}$.

Thus, we can conclude that options $\left(A\right),\left(B\right)$ and $\left(D\right)$ are the correct answers.