Magnetism

Question 1

Where are the magnetic forces the strongest on magnets?

Answer 1

At the poles

Question 2

What do two like poles and unlike poles to do one another?

Answer 2

Two like poles repulse each other.

Two unlike poles attract each other

Question 3

Attraction and repulsion between two magnetic poles are examples of what?

Answer 3

Non-contact force.

Question 4

What is a permanent and induced magnet?

Answer 4

Permanent= produces its own magnetic field

Induced = material that becomes a magnet once placed in a magnetic field

Question 5

What does induced magnetism always cause?

Answer 5

A force of attraction

Question 6

Definition of magnetic field?

Answer 6

The region around a magnet where a force acts on another magnet

Question 7

What factor effects the strength of the magnetic field?

Answer 7

The distance from the magnet

Question 8

Why does Earth have a magnetic field?

Answer 8

Due to the moving liquid iron in the core

Question 9

What happens when a current flows through a conducting wire?

Answer 9

A magnetic field is produced around the wire

Question 10

Two factors that affect the strength of the magnetic field in terms of current?

Answer 10

Depends on the current flowing through the wire and distance from the wire

Question 11

How to work out direction of field?

Answer 11

Use the right hand grip rule

• Right hand gripping the wire with the thumb pointing in the direction of current flow. The direction of fingers show the direction of the field.

Question 12

What can a coil also be called?

Answer 12

Solenoid

Question 13

What does shaping a wire into a solenoid do and why?

Answer 13

Increases strength of magnetic field created by current through wire. The weak field of each section of the solenoid combines t create a single stronger field.

Question 14

What is an electromagnet?

Answer 14

A solenoid with an iron core

Question 15

What is the N pole and S pole connected to in a solenoid?

Answer 15

North pole is connected to negative while South pole is connected to positive

Question 16

What is the motor effect?

Answer 16

When a conducting wire carrying an electrical current is placed in a magnetic field, the magnet producing the field and the conductor exert a force on each other.

Question 17

What is Flemming’s left hand rule used to find out?

Answer 17

The direction of the motor effect force

Question 18

What does each finger represent in Flemming’s left hand rule?

Answer 18

First finger = magnetic field
Second = current (points towards negative)
Thumb= direction of force

Question 19

Three factors that affect the size of the force on the conductor are?

Answer 19

The length of the conductor within the field

Strength of the magnetic field

Amount of current flowing

Question 20

What position must the conductor be at to the magnetic and why?

Answer 20

Must be at a right angle to the magnetic field for the maximum force to be generated

Question 21

What is magnetic flux density measured in?

Answer 21

Tesla

Question 22

What does a coil of wire carrying a current tend to do?

Answer 22

Rotate within a magnetic field

Question 23

How can a simple electric motor be built?

Answer 23

1. Use a coil of wire free to rotate between two opposite magnetic poles.
2. When an electric current flows through the coil, the current is moving in opposite directions on each side on coil.
3. As a result, the coil rotates
4. Direction of current must be reversed every half turn, otherwise the coil comes to a halt
5. To avoid that, a split ring/commutator will help. That increases the effect of the magnetic field.

Question 24

How do loudspeakers and headphones work?

Answer 24

1. Use the motor effect to convert variations in current in electric circuits to the pressure variations in the sound waves.
2. When AC is applied to coil, it produces a constantly varying magnetic field.
3. The field is attracted or repulsed by the field of the fixed magnet causing vibrations in the speaker ear.
4. That transmits vibrations to the air and produces sound waves

Question 25

What is the generator effect?

Answer 25

• If an electrical conductor is moving through a magnetic field/there is a change in the magnetic field itself, a voltage s induced across the end of the conductor.
• If the conductor is connected to an electrical circuit, a current is induced in the conductor.

Question 26

When is the current reversed in induced potential topic?

Answer 26

• the magnet is moved out of the coil
• other pole of magnet is moved into the coil

Question 27

An induced voltage or current will increase if?

Answer 27

• The speed of movement is increased
• The magnetic field strength is increased
• The number of turns on the coil is increased

Question 28

What do cars use and why?

Answer 28

An alternator to keep the battery charged and to run the electric system while the engine is working.

Question 29

What happens to the voltage during the rotation?

Answer 29

The side that is moving up a voltage is induced in one direction.

The side that moves down is where the induced voltage reverses direction.

That creates an alternating current

Question 30

What happens in a dynamo?

Answer 30

-The split rings change the coil connections every half turn.
- As the induced voltage is about to change in direction, the connections are reversed.
-This means the current to the external circuit always flows in the same direction.

Question 31

What does the microphone convert?

Answer 31

Sound waves into electrical waves

Question 32

How does a moving-coil microphone work?

Answer 32

1. Pressure vibrations in sound waves cause the flexible diaphragm to vibrate
2. Vibrations of diaphragm cause vibrations of the coil
3. Voltage is induced in the coil
4. Coil is apart of a complete circuit, so induced voltage causes a current to flow around the circuit.
5. The changing size of the direction and induced current matches the vibrations of the coil
6. The electrical signals generated, match the pressure variations in the sound waves