An electromagnet is a temporary magnet due to which of the following?

the magnet is only present when a current is present.
the magnet is only present when the domains are not aligned.
the magnet is only present when the current is turned off.
the magnet is only present when the resistance is high.

The magnet is only present when a current is present.

Explanation:

As we know that in electromagnet there is a coil of certain resistance which is connected to a energy source which will provide constant potential difference to the coil

Due to constant potential difference the coil will have a current flow in it due to which there exist a magnetic field along the axis of the coil

this magnetic field is only possible when current is flowing in the coil

So it is given as

here we know

N = number of turns

L = length of solenoid

i = current in it

So correct answer is

The magnet is only present when a current is present.

pe = weightxheight = 2000x1000=2,000,000joules