CP10 - Magnetism and the motor effect

Effect of two like poles on each other, and two unlike poles on each other.

Repel, attract

Permanent magnet

An object that always has a magnetic field around it.

Three magnetic materials

Iron, cobalt, nickel

Induced magnet

A magnetic material that becomes a magnet when inside another magnetic field.

Electromagnet

A magnet produced when current flows through a coil of wire.

What happens when current stops flowing through a coil of wire?

Magnetic field disappears

Where is a magnetic field strongest?

Where the field lines are closest together.

What does the needle of a compass show?

The needle points in the direction of the North Pole.

What does the strength of a magnetic field around a current depend on?

Size of current and distance from the wire.

How can you make an electromagnet stronger?

More coils or more current.

Why is field strongest inside and weakest outside a solenoid?

Magnetic fields from the individual coils add together to make the overall field stronger.

Magnetic fields from the individual coils cancel making the overall field weaker.

How can we determine the direction of the magnetic force on a current carrying wire?

Fleming’s left hand rule

Equation for the force on a current carrying wire

F (magnetic force) = B (magnetic field strength) x I (current) x L (length of conductor)

How does a magnetic force cause rotation in an electric motor?

The forces produce moments on a wire.

What causes magnetic forces?

The interaction of magnetic fields.

What happens if a current carrying wire is placed in a magnetic field?

The wire experiences a force (and the magnet experiences an equal and opposite force).

Shape of magnetic field around the solenoid?

Same as a bar magnet.

Shape of magnetic field around a current carrying wire

Ring around wire (if you grabbed wire with right hand, thumb in direction of conventional current, your fingers will go the same direction as the the magnetic field).

Uniform magnetic field

Between two magnets, straight lines between north and south poles of the two different magnets.

Shape of magnetic field around a bar magnet.

Curved lines from North Pole to South Pole with increasing radius, one field line going straight away from the North Pole and straight to the South Pole.