Physics - MAGNETISM AND ELECTROMAGNETISM (P7)

Permanent & Induced Magnetism, Magnetic Fields -

What are the only three magnetic elements?

Iron, cobalt, + nickel.

Permanent & Induced Magnetism, Magnetic Fields -

What is a permanent magnet?

A magnet that produces its own magnetic field + retians its magnetism.

Permanent & Induced Magnetism, Magnetic Fields -

What is an induced magnet?

A material that becomes magnetic only when placed in a magnetic field.

Permanent & Induced Magnetism, Magnetic Fields -

What is the direction of magnetic field lines?

Form north to south outside the magnet.

Permanent & Induced Magnetism, Magnetic Fields -

How can you detect a magnetic field?

Using a compass.

Permanent & Induced Magnetism, Magnetic Fields -

What happens to an induced magnet when the magnetic field is removed?

It loses its magnetism.

Permanent & Induced Magnetism, Magnetic Fields -

Where is the magnetic field strongest?

At the poles of a magnet.

Magnetic Fields + Electric Currents -

What is created around a wire when current flows through it?

A circular magnetic field.

Magnetic Fields + Electric Currents -

How can you increase the strength of the magnetic field around a wire?

Increase the current / wrap the wire into a coil (solenoid).

Magnetic Fields + Electric Currents -

What’s a solenoid?

A coil of wire that produce a strong magnetic field when current flow through it.

Magnetic Fields + Electric Currents -

How can you increase the strength of a solenoid’s magnetic field?

Add an iron core, increase current, / increase number of turns.

Magnetic Fields + Electric Currents -

What type of magnet is an electromagnet?

An induced magnet that can be turned on + off w/ current.

Uses of Electromagnets -

Name three uses of electromagnets.

Electric bells, scrap yard cranes, magnetic clocks, relays.

Uses of Electromagnets -

Why are electromagnets useful in cranes?

Because they can be swicthed on + off to pick up + drop metal objects.

Uses of Electromagnets -

What happens in an electric bell when the circuit is completed?

The electromagnet attracts a striker that hits the bell + breaks the circuit, which then reforms repeatedly.

The Motor Effect -

What is the motor effect?

A force exerted on a current-carrying wire in a magnetic field, causing motion.

The Motor Effect -

What factors affect the size of the motor effect force?

Size of current, strength of magnetic field, + length of wire in the field.

The Motor Effect -

What is the equation for the force on a conductor in a magnetic field?

F = BIL

Force = magnetic flux density x current x length

The Motor Effect -

What are the units for the quantities in F = BIL ?

F: Newtons (N)

B: Tesla (T)

I: Amperes (A)

L: Metres (m)

The Motor Effect -

How can you reverse the direction of the force in the motor effect?

Reverse the current / the magnetic field direction.

Electric Motors -

What basic principle is used in an electric motor?

The motor effect.

Electric Motors -

How does a simple DC motor work?

A coil of wire rotates in a magnetic field due to forces on the two sides of the coil, w/ a split-ring commutator reversing the current every half-turn to maintain rotation.