How to make the motor turn the other way
If you have a motor spinning (as shown below) in an anti-clockwise direction, how would you make the motor turn in the other direction?
Reverse the current
One way to change the direction of the motor is to reverse the battery. In reversing the battery you also reverse the current supply. See below:
If you compare drawing A with the drawing above and use Fleming's left hand rule, you will find that the forces on the coil of wire have reversed and therefore the motor spins in the other direction.
Reverse the magnetic fields
Another way to change the direction of the motor is to reverse the positions of the magnetic fields (N and S) . See below:
If you compare drawing A with the drawing above and use Fleming's left hand rule, you will find that the forces on the coil of wire have reversed and therefore the motor spins in the other direction.
Reverse the current and the magnetic field
You can take the arrangement of the magnet, battery and wire coil in drawing A and reverse the positions of the magnetic fields (N and S) and also reverse the battery. See below:
What is interesting is that if you use Fleming's left hand rule to now work out the forces on the wire coil you will find there is NO CHANGE in the direction the shaft spins. This is because the reversal of the battery in effect cancels out the reversal of the magnetic fields, so we are left with the same direction of rotation.
