A magnet relay is a device used for?

Analyze the question

The question asks about the purpose of a magnetic relay, a common topic under electromagnetism and its applications.

Explain the concept

A relay is an electromagnetic switch. It has these main parts:

• A coil (electromagnet) wound on a soft iron core
• An armature (a movable piece of iron)
• Contacts, which open or close the second circuit

Show the solution

1. A small current in the control circuit flows through the coil.
2. The coil becomes an electromagnet and attracts the soft iron armature.
3. The armature movement closes (or opens) the contacts of a second circuit.
4. This second circuit can carry a much larger current, such as a motor, a car starter, or a heavy-duty lamp.

So a relay lets a weak current switch on a circuit carrying a large current. It also keeps the two circuits electrically separate, which is safer.

Checking the options

• A. Reading the magnitude of magnetic flux: this describes a fluxmeter, not a relay.
• B. Controlling another circuit carrying larger current: correct.
• C. Turning in sports: not related to physics.
• D. Storing magnetic field: this is closer to what an inductor does.

Answer: Option B.

Exam tip

Remember: Relay = Remote switch. A small current in one circuit controls a big current in another. Examples are the car starter motor and the electric bell or buzzer circuits.