Applying the motor principle to explain important applications such as electric meters or electric motors.
The motor principle states that when an wire carrying an electric current is placed in an external magnetic field it experiences a force that can cause the wire to move. The direction and strength of the force depends upon the strength of the magnetic field, the amount of current, the length of the wire, the direction of the magnetic field and of the direction of the wire.
One basic application is to make the current flow through a loop. This can cause the loop to twist or rotate. In an electric meter the loop is connected to a needle. The amount of the current in the loop determines the amount that the needle moves. This helps us measure quantities such as current.
In a motor the loop is set up so that it twists constantly if a steady current flows through the loop. Connecting the loop to an axle or drive shaft then allows the loop to drive a motor such as a fan or drill or washing machine.