Which action is the best way to turn an electromagnet off?

1) The strength of the electromagnet increases   →   Place a magnetic core inside the coil of wire

2) The electromagnet turns off    →    Turn off the battery supply

3) The poles of the electromagnet reverse     →    Change the direction in which the current flows

Explanation:

when current passes through a coil it behaves a an electromagnet.

Magnetic field strength is given by

B = μ N I  

N is no of turns and

I is the current through coil

μ is permeability of the medium or core in the coil.

1). Magnetic core increase permeability μ so it will strengthen magnetic field:

B = μ N I

2). When the battery turns off current becomes zeroi.e I=0

So B = μ N * 0

⇒ B = 0

so electromagnet turns off

3). Direction of magnetic field can be determine by right hand rule, i.e curl the fingers in the direction of current, thumb will point in the direction of north pole.

so changing current direction will change direction of magnetic field.

add a switch to the electrical circuit

Explanation:

A P E X

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