Magnetic field around a current carrying loop
So far we have only looked at straight wires carrying a current and the magnetic fields around them. We are going to study the magnetic field set up by circular loops of wire carrying a current because the field has very useful properties, for example you will see that we can set up a uniform magnetic field.
Optional Activity: Magnetic field around a loop of conductor
Imagine two loops made from wire which carry currents (in opposite directions) and are parallel to the page of your book. By using the Right Hand Rule, draw what you think the magnetic field would look like at different points around each of the two loops. Loop 1 has the current flowing in a counter-clockwise direction, while loop 2 has the current flowing in a clockwise direction.
If you make a loop of current carrying conductor, then the direction of the magnetic field is obtained by applying the Right Hand Rule to different points in the loop.
Notice that there is a variation on the Right Hand Rule. If you make the fingers of your right hand follow the direction of the current in the loop, your thumb will point in the direction where the field lines emerge. This is similar to the north pole (where the field lines emerge from a bar magnet) and shows you which side of the loop would attract a bar magnet’s north pole.