Question

When a solenoid is activated, the force that moves the plunger is
A. an electromagnetic field
B. a permanent magnetic field
C. varying voltage
D. steady current

Answer 1

Hint: In this question we are asked to find the force that moves the plunger, when the solenoid is activated. Therefore, to answer the question we shall discuss what is the solenoid and its construction. While discussing that we shall also discuss how the plunger is moved. We know that a solenoid can be used as an electromagnet.

Complete answer:
A solenoid is a coil of wire used as an electromagnet. The purpose of solenoid is to generate a controlled magnetic field through a coil wound into tightly packed helix. Solenoid is made of many turns of wire wrapped around a magnetic assembly. When an electric current is passed through the coil, an electromagnetic field is produced, this causes the armature to be pulled towards the coil. The magnetic field of the solenoid is as shown in the figure below.

         

Therefore, from above facts we can say that, when solenoid is supplied with current, the plunger moves towards the coil due to electromagnetic force.

So, the correct answer is “Option A”.

Note:
 The name solenoid was termed by a French physicist, Andre-Marie Ampere to designate a helical coil. The core material of solenoid is ferromagnetic in nature. This means that there is concentration of magnetic flux lines. The coil whose length is greater than its diameter can also be termed as a Solenoid.