Question

The telegraph was one of the first machines that could send a message almost instantly to someone hundreds of miles away. The telegraph used a current to turn an electromagnet on and off. When the electromagnet was on it was attracted to a metal plate and it would tap. A series of taps was used to send a message.

How can a current in a wire be used to make an electromagnet?
A.
wrap the wire around a magnet
B.
hold a magnet just touching the wire
C.
add a stronger battery to the wire
D.
wrap the wire around a piece of iron

Answer 1

D. wrap the wire around a piece of iron

When current flows in the wire it creates a magnetic field; winding the wire into a coil around an iron core concentrates and strengthens that field, making an electromagnet.