Currents and magnetic fields
All currents have a magnetic field around them. All the cables connecting electrical appliances to the mains in your home will have magnetic fields around them, and so do the large electricity power lines you can see on pylons outside.
A straight wire has a circular magnetic field around it. A coil of wire has a magnetic field around it, that is the same shape as a bar magnet.
If the conventional current flows the other way, the magnetic field will be in the opposite direction. As you move further away from the wire, the magnetic field gets weaker, which is why the lines are drawn further apart.
These types of magnets are called electromagnets. They are temporary magnets as they can be turned on and off with the current. Normal bar magnets are permanent magnets because it is very difficult for them to lose their magnetism.
Electromagnets are far more useful than permanent magnets because:
- They can be switched on and off.
- The strength of the magnetic field can be changed…