magnetism

At which parts of a magnet is the magnetic forces most strongest

At the poles

What happens when two magnets are brung close to each other

They exert a force on each other

What force is exerted when two like poles are brought close

They repel

What force is exerted if two opposite poles are brought Close together

They attract

What is attraction and repulsion between 2 magnetic poles an example of

Non-contact force as magnets dont have to touch to experience a force

What is a permanent magnet

A magnet that produces its own magnetic field

What is an induced magnet

A magnet that has to be put inside a magnetic field to become magnetic

What type of force does induced magnets always cause

Force of attraction

What happens when an induced magnets is removed from magnetic field

Looses all/most of its magnetism

What is an magnetic field

The space around a magnetic field where there eis a non-contact force on a magnetic material

Give 4 examples of magnetic materials

1. Cobalt

2. Nickel

3. Steel

4. Iron

What is always said about a force between a magnet and a magnetic material

It is always attractive

What does the strength of a magnetic field depend on

How close the field lines are

If the field lines are closer, what does that tell you

The magnetic field is stronger

If the magnetic field is weaker, how can we tell

If the field lines are further apart

How does strength of a magnetic field change as you move further away from the magnet producing it

Decreases as you move further away

What direction do magnetic field point

North to south poles

What does a magnetic compass have

A small bar magnet that points in the direction of the earths magnetic field

What direction does compass point when not near a magnetic material and why

North as earth has an iron core which is magnetic

What is produced when current flows through a conducting wire?

A magnetic field is produced around the wire

What happens if you change direction of current

change the direction of the magnetic field

What does strength of a magnetic field depend on, name 3

1. Size of current

2. Distance of magnetic field from wire

3. How close the field lines are

How to increase strength o magnetic field

1. Increase current

2. Move magnetic field closer to wire

What is a solenoid

A coil of wire which when current flows through, it creates a strong magnetic field

Describe the magnetic field found inside a solenoid

Strong and uniform

What is an electro-magnet

A solenoid with an added iron core

How to increase strength of magnetic field in a solenoid (Name three)

1. Increase turns in the wire

2. Add iron core

3. Increase current flowing through wire

Why are electro-magnets useful?

• Magnetism able to be turned on and off

• Can increase strength of magnetic field easily by increasing current so strength easily controlled

• Can be made very strong

Give 3 examples where electro magnets are used

1. Electric motors like fans and hairdryers

2. MRI scanners in hospitals

3. Cranes

4. Electric bell

What is the RIGHT hand thumb rule

• point thumb in direction of current

• Curl fingers in direction of magnetic field

How could u also increase strength of a magnetic field that a wire produces

Wrap a wire in a coil (make it a solenoid)

Why dos adding a solenoid increase magnetic field around wire

Field lines around loop of wire line up with each other so they are brung closer together

What is the motor effect?

When a force is exerted between a magnetic field and a current carrying wire or any conductor which causes the wire to move by being placed in a magnetic field

What happens in motor effect

• current carrying wire or any conductor is put inside a magnetic field

• Magnetic field around the wire interacts with magnetic field

• Which causes wire and magnet to exert a force on each other

• Which causes wire too move

When is force maximum and why

When wire is perpendicular (90 degrees) to magnetic field because wire is crossing maximum amount of field lines

When is force at zero and why

When wire is parallel to magnetic field as its not crossing field lines

What role is used to determine the force exerted due to motor effect

Flemmings LEFT hand rule

Explain Flemmings left hand rule- what does thuMb represent

MOTION- direction of force

Flemmings left hand rule- what does second finger represent

Direction current is flowing

Flemmings left hand rule- what does First Finger represent

Direction of Field

What do dots represent in diagrams

Current is coming out so point finger out

What do crosses represent in a diagram

Current going in so point fingers into page

Which way do fingers have to point?

North to south

What is the equation and what does each part stand for

F= BIL

What does the F stand for in the equation

Force on the wire, measured in newtons

What does B stand for in equation

Magnetic flux density, measured in tesla

What does I stand for in equation

Amount of current flowing in wire, measured in AMPS

WHAT DOES L STAND FOR EQUATION

Length of wire, measured in metres

Which way does current always flow

From positive (+) to negative (-)

What factors affect size of force on a current carrying wire in a magnetic field

• magnitude of current flowing through conductor

• The strength of magnetic field that conductor or current carrying wire is placed in

What affects size of force on a current carrying wire in a magnetic field

• magnitude of current flowing through wire

• Strength of magnetic field the wire is placed in

If the strength of current carrying wire placed in a uniform magnetic field is increased, what happens to force

Strength of force increases

What do electric motors do

Convert electric energy into mechanical energy to produce momentum

What is momentum

A turning effect

What are electric motors powered by

DC- direct current

What is direct current produced by

Batteries and cells

What does basic dc motor do

Allows force to act on two arms of coil of wire that carry current

Explain the process of electric motors

1. When electric current flows through coil, the coil experiences a force and moves

2. The opposite forces on each side attract and causes coil of wire to rotate (creating momentum)

3. A split ring commutator is needed to keep coil spinning

4. When commutator revered, direction of current is reversed in each side

5. This means force on left side is always upwards due to its own momentum

6. When coil is vertical there is no current as no connection to battery so no force on coil

7. But coil continues to turn as force on right is always downwards

What does split ring commutator do

Reverses current in coil for every half turn to keep coil spinning

When coil has spun quarter turn from horizontal, there is no force why

Split ring commutator has no connection to battery so there will be no current flowing through wire so no force