Inductive Circuit and AC Mains

An inductive circuit is a type of electrical circuit that contains an inductor, which is a passive electronic component that stores energy in the form of a magnetic field. When an alternating current (AC) is applied to an inductive circuit, the inductor resists changes in current flow, causing a phase shift between the voltage and current waveforms.

The AC mains, also known as the power mains or the electrical grid, is the system of power generation, transmission, and distribution that supplies electricity to homes, businesses, and industries. The AC mains typically provide a sinusoidal voltage waveform with a fixed frequency.

Power in an Inductive Circuit

The power in an electrical circuit can be calculated using the formula:

P = VIcos(θ)

where P is the power, V is the voltage, I is the current, and θ is the phase angle between the voltage and current waveforms.

In an inductive circuit, the phase angle θ is positive, indicating that the current lags behind the voltage. This means that the current waveform reaches its peak value after the voltage waveform. As a result, the power factor (cos(θ)) in an inductive circuit is less than 1, leading to a power dissipation that is lower than the product of the voltage and current magnitudes.

Power Consumption in the Inductive Circuit

In order for a circuit to consume power from the AC mains, the power factor must be positive. This means that there must be a phase angle θ between the voltage and current waveforms such that cos(θ) > 0.

Explanation of the Correct Answer

The correct answer to the given question is option 'C' - "applied voltage decreases but current increases".

When the applied voltage decreases in an inductive circuit, it results in a decrease in the magnitude of the voltage waveform. However, the inductor resists changes in current flow, so the current waveform takes some time to decrease. As a result, the phase angle between the voltage and current waveforms increases, leading to a positive power factor and power consumption from the AC mains.

In other words, when the applied voltage decreases, the inductive circuit still maintains a significant current flow, resulting in power being drawn from the AC mains.

Conclusion

In summary, a purely inductive circuit takes power from the AC mains when the applied voltage decreases but the current increases. This is because the inductor resists changes in current flow, causing the current waveform to lag behind the voltage waveform and leading to a positive power factor.