c) Electromagnetism

What does an electric current in a conductor produce?

A magnetic field around it.

Larger the current, stronger the magnetic field

Direction of magnetic field depends on direction of current.

Why is a force exerted on a current-carrying wire?

Because when the wire is placed between two magnetic poles the two magnetic fields affect each other resulting in a force on the wire causing it to move which is known as the motor effect.

At what angle will the wire have to be to feel full force, no force, some force?

90 degrees to magnetic field.

If wire is along magnetic field it wont feel any force.

Angle in between it’ll feel some force.

How is the motor effect applied in a electric motor?

1. Current flows in wire.

2. This creates a magnetic field.

3. The magnetic field interacts with the field from permenant magent.

4. This produces force on wire causing it to move.

5. The split-ring commutator changes the direction of the current as it spins.

6. This reverses the direction of force, allowing wire to continue spinning.

How is the motor effect applied in a loudspeaker?

1. A.c electrical signals from an amplifier are fed into coil of wire in the speaker which is wrapped around the base of a cone.

2. Coil is surrounded by a permanent magnet meaning a.c signals cause force on coil and makes it move back and forth.

3. These movements make cone vibrate creating sounds.

Rules Flemings left hand?

Thumb - direction of force(Motion)

First finger - direction of magnetic field

Second finger - direction of current

How does the force of a current-carrying conductor in a magnetic field change with the magnitude and direction of the field and current?

Increase magnitude of current through wire or size of magnet being used. , increases force on wire.

Change direction of current or reverse poles of magnet, changes direction of the force on wire.