The motor effect

What happens when a current flows through a conducting wire?

A magnetic field is produced around the wire. The strength of the magnetic field depends on the current through the wire and the distance from the wire.

How can the strength of the magnetic field created by a current through the wire be increased?

Shaping a wire to form a solenoid. Adding an iron core increases the strength of the magnetic field of a solenoid.

Why does a solenoid increase the strength of the magnetic field?

The field lines around each loop of wire line up with each other.

What is an electromagnet?

A solenoid with an iron core.

What is the motor effect?

When a conductor carrying a current is placed in a magnetic field the magnet producing the field and the conductor exert a force on each other

What are the factors that affect the size of the force on the conductor?

• Current: The larger the current, the larger the force.

• Length: The longer the length of the conductor, the larger the force.

• Magnetic Flux Density: The higher the density, the more magnetic field lines and the larger the force on the conductor.

What does a coil of wire carrying a current in a magnetic field tend to do?

Rotate; this is the basis of an electric motor.

How does the force on a conductor in a magnetic field cause the rotation of the coil in an electric motor?

The current creates a magnetic field around the wires of the coil. The field from the coil interacts with the field of the permanent magnet. That makes each of the sides of the coil parallel to the magnet experience a force. This force pair acts in opposite directions making the coil rotate.