Introduction:
A single phase half wave rectifier circuit is used to convert an alternating current (AC) input into a pulsating direct current (DC) output. It consists of a diode and a load connected in series. The diode allows current to flow in only one direction, resulting in the rectification of the AC signal. However, when the AC input voltage is negative, the diode blocks the current flow, causing a high voltage spike. This can damage the diode and the circuit. To protect the diode and prevent the voltage spike, a freewheeling diode is used.

The Function of a Freewheeling Diode:
The freewheeling diode, also known as a flyback diode or a snubber diode, is connected in parallel to the load in a half wave rectifier circuit. Its main purpose is to provide a low impedance path for the current when the diode is reverse biased, allowing the energy stored in the inductive load to dissipate safely. It acts as a "freewheel" for the current to flow through in the reverse direction, preventing voltage spikes and protecting the circuit.

Explanation of Options:
a) If the load is purely resistive, it does not contain any inductance. In this case, there is no energy stored in the load that needs to be dissipated. Therefore, the freewheeling diode does not conduct.

b) If the load is purely inductive, such as an electromagnet or a motor, it stores energy in its magnetic field when current flows through it. When the AC voltage becomes negative and the diode blocks the current, the energy stored in the inductive load would create a high voltage spike. The freewheeling diode conducts in this case to provide a path for the current to flow and dissipate the stored energy safely.

c) If the load is a combination of resistance and inductance, the freewheeling diode will conduct when the AC voltage becomes negative. It allows the current to flow through the diode and dissipate the energy stored in the inductive load. This protects the circuit and prevents voltage spikes.

Conclusion:
In a single phase half wave rectifier circuit, the freewheeling diode conducts when the load is purely inductive or a combination of resistance and inductance. This is because inductive loads store energy that needs to be dissipated safely when the diode blocks the current. By providing a low impedance path for the current, the freewheeling diode protects the circuit from damage and prevents voltage spikes.

Explanation:

A single-phase half-wave rectifier circuit is used to convert an alternating current (AC) input voltage to a pulsating direct current (DC) output voltage. In this circuit, a diode is used to rectify the AC voltage by allowing current to flow in one direction only.

Free wheeling diode:

A free-wheeling diode, also known as a flyback diode or a snubber diode, is connected in parallel with the load in a rectifier circuit. Its purpose is to provide a path for the current when the AC supply voltage is negative or when the diode is reverse-biased.

Conduction of the free-wheeling diode:

The free-wheeling diode will conduct only under specific conditions. Let's consider the different load scenarios:

a) Load is purely resistive:
In this case, the load is purely resistive, meaning it does not have any inductance. When the AC supply voltage is positive, the diode in the rectifier circuit conducts and the load receives the current. When the AC supply voltage is negative, the diode is reverse-biased and the load does not receive any current. Therefore, the free-wheeling diode does not conduct in this case.

b) Load is purely inductive:
In this case, the load is purely inductive, meaning it consists of an inductor. When the AC supply voltage is positive, the diode in the rectifier circuit conducts and the load receives the current. When the AC supply voltage is negative, the inductor tries to maintain the current flow, creating a back EMF (electromotive force) that opposes the change in current. This back EMF can cause a voltage spike, which can damage the circuit or the diode. To protect the circuit, the free-wheeling diode conducts and provides a path for the current, allowing the inductor to discharge safely. Therefore, the free-wheeling diode conducts in this case.

c) Load is a combination of resistance and inductance:
In this case, the load consists of both resistance and inductance. The behavior of the free-wheeling diode will depend on the relative values of resistance and inductance. If the inductance is dominant, the behavior will be similar to case b) and the free-wheeling diode will conduct. If the resistance is dominant, the behavior will be similar to case a) and the free-wheeling diode will not conduct.

Conclusion:

The free-wheeling diode in a single-phase half-wave rectifier circuit will conduct only if the load is purely inductive or a combination of resistance and inductance. This is because inductive loads can create back EMF when the current changes, and the free-wheeling diode provides a path for the current to discharge safely.