P4 - Magnetism and magnetic fields

what is the difference between a permanent magnet and an induced magnet?

Induced magnets will (usually) lose their magnetism once the magnet has moved away

What shape is the magnetic field around a straight current carrying wire?

Concentric circles in an anticlockwise motion

What is a solenoid?

Coils/ loops of wire

How can the magnetic effect of a solenoid be increased?

• increase current

• Increase number of coils/turns

• Add an iron core inside the solenoid

• Decrease the cross - section of the solenoid

• Decrease the length of the solenoid

What happens when a current carrying wire is placed between magnetic poles?

There is a force on the wire

How is the force on the wire increased?

If the current or the magnetic field is made stronger

What happens to the direction of the force if the magnetic field or current change direction?

The force changes direction

What does flemming’s left hand rule show?

• First finger is the direction of the magnetic Field

• SeCond finger is the direction of the Current

• Thumb is the direction of Motion (force)

Force on a conductor carrying a current (N) = magnetic flux density (T) x current (A) x length (m)

How can the speed of a motor be increased?

• increase current

• Add more turns to the coil

• Increase the magnetic flux density