The coil magnet
A coil with current acts like a magnet.
A nail that lifts clips
An iron nail is wrapped with wire. The wire is joined to a battery. When the circuit is closed, the nail picks up iron paper clips. When it is opened, the clips fall off.
What do you think makes the nail pick up the clips?
What this lesson covers
The idea
A current-carrying coil that behaves as a magnet is called an electromagnet; it loses its magnetic effect when the current is stopped, and an iron core inside the coil makes it a much stronger magnet.
A nail that lifts clips
An iron nail is wrapped with wire. The wire is joined to a battery. When the circuit is closed, the nail picks up iron paper clips. When it is opened, the clips fall off.
What do you think makes the nail pick up the clips?
- The electric current in the coil
- A hidden magnet inside the wire
- Pure luck
Switch on the coil
Press the switch to turn the current ON. Then put the iron nail inside the coil.
A magnet that switches off
The coil turned the compass needle and picked up clips. With the nail inside it did this much more strongly. Switch the current off and it lost its effect.
A current carrying coil that behaves as a magnet is called an electromagnet. It loses its magnetic effect when the current stops. An iron core inside the coil makes it a stronger magnet.
Notes
A current carrying coil that behaves as a magnet is an electromagnet. It loses its effect when the current stops. An iron core makes it stronger.
Check yourself
A current carrying coil that behaves as a magnet is called …
The current through an electromagnet is stopped. The coil …
Why do most electromagnets used in practice have an iron core?
Iron clips cling to a coil only when …
- an electromagnet — correct. Yes!
- a battery. A battery supplies current. It is not the coil that acts as a magnet.
- a compass. A compass is a tiny magnet used to detect a magnetic field.
- keeps all its pull. It loses its magnetic effect when the current stops.
- loses its magnetic effect — correct. Yes!
- gets stronger. Stopping the current removes the effect. It does not add to it.
- It makes them lighter. The core is there to make the magnet stronger, not lighter.
- It stops the current. The current still flows. The iron core only makes the magnet stronger.
- The iron core makes them stronger — correct. Yes!
- current flows through the coil — correct. Yes!
- the coil is switched off. With the current off, the coil loses its magnetic effect.
- the coil is far away from the clips. What makes the coil a magnet is the current, not the distance.