Magnetism - Paper 2

Question 1

What will two north poles do to each other?

Answer 1

Repel

Question 2

What will two south poles do to each other?

Answer 2

Repel

Question 3

What will a south and north pole do to each other?

Answer 3

Attract

Question 4

Is mangentism an example of a contact or non contact force?

Answer 4

Non contact

Question 5

State some differences between permanent and induced magnets

Answer 5

1. A permanent magnet always has a magnetic field.
2. An induced magnet only becomes magnetic when placed in a magnetic field.
3. Induced magnets always causes force of attraction.
4. Permanent magnets can attract or repel

Question 6

State the magnetic materials

Answer 6

1. Iron
2. steel
3. cobalt
4. nickel

Question 7

What do we call the region around a magnet where a force acts on another magnetic material?

Answer 7

Magnetic field

Question 8

Which direction do magnetic field lines point in?

Answer 8

North to South

Question 9

What do magnetic fields line show?

Answer 9

1. The closer the fields lines the stronger the field.
2. The arrows show the direction of force a north pole would feel.

Question 10

Describe the magnetic field pattern around a bar magnet

Answer 10

Field lines loop from the North pole to the south pole

Question 11

What is the relationship between the size of attraction/repulsion and distance from a magnet

Answer 11

As distance increase the force or field gets weaker

Question 12

Where is the strength of a magnetic field the strongest?

Answer 12

The poles of a magnet

Question 13

Why do magnetic field lines always need arrows on them?

Answer 13

The direction of the magnetic field at any point is given by the direction of the force that would act on another north pole placed at that point.

Question 14

Describe how a magnetic compass works

Answer 14

A magnetic compass contains a small bar magnet.

The Earth has a magnetic field. T

he compass needle points in the direction of the Earth’s magnetic field.

Question 15

Describe how a magnetic compass can be used to find the pattern around a bar magnet.

Answer 15

1. Put the magnet in the middle of the piece of paper and draw around it.
2. Draw nine dots around the north end of the magnet.
3. Put a plotting compass on the paper so that its tail is over one of the dots.
4. Draw a dot on the paper near to the point of the compass.
5. Join the two dots and mark the line with an arrow.
6. Then move the compass so that its tail is over your new dot.
7. Make another dot next to the point.
8. Repeat until you come to the edge of the paper or loop back round to the south pole.

Question 16

When a current flows what is always created?

Answer 16

A magnetic field

Question 17

Describe the magnetic field pattern around a straight wire carrying a current.

Answer 17

In circualr loops around the wire.

Question 18

Describe the right hand rule for a straight wire carrying a current

Answer 18

Thumb points in the direction of the current, fingers curl around in the direction of the magnetic field

Question 19

What factors affect the strength of the magnetic field produced by a current?

Answer 19

1. Size of the current
2. Distance from the wire

Question 20

What is a solenoid?

Answer 20

When a current carrying wire is turned into a coil. this will increase the strength of the magnetic field.

Question 21

Describe the magnetic field inside a solenoid

Answer 21

The magnetic field inside a solenoid is strong and uniform. This is shown by parallel staight lines that are close to each other.

Question 22

Describe the magnetic field around a solenoid

Answer 22

The magnetic field around a solenoid has a similar shape to that of a bar magnet. It loops from North to South

Question 23

How can a solenoid be turned into an electromagnet?

Answer 23

Adding an iron core, this again increases the strength of the magnetic field.

Question 24

Describe the magnetic field of an electromagnet

Answer 24

Its the same as a bar magnet

Question 25

How can the strength of an electromagnet be increased?

Answer 25

1. Larger current
2. More turns
3. Using an iron core

Question 26

What is the motor effect?

Answer 26

When a conductor carrying a current is placed in a permanet magnetic field. The magnet fields from the magnet and the current exert a force on each other.

Question 27

Describe Fleming’s left hand rule.

Answer 27

Thumb, first finger and second finger are put at right angles to each other.

Thumb - direction of force/motion

First Finger - direction of magnetic field (always from North to south)

seCond finger - direction of current (always from positive to negative)

Question 28

In the motor effect how can the size of the force be increased?

Answer 28

1. Larger current
2. Stronger permanent magnets
3. Longer length of wire inside the magnetic field
4. Keeping the conductor at a right angle to the magnetic field

Question 29

In the motor effect how can the direction of the force be reversed?

Answer 29

1. Reversing the direction of the current
2. Reversing the poles of the permanent magnets

Question 30

State the units for magnetic flux density.

Answer 30

Tesla (T)

Question 31

Describe how a coil of wire inside a magnetic field can cause rotation eg an electric motor

Answer 31

The current goes into the coil of wire, creating an electromagnetic field.

This interacts with a the permanent magnetic field causing a force of attraction or repulsion.

The current then comes out of the coil changing direction so the force changes direction. This causes rotation.

Question 32

How do loudspeakers/headphones use the motor effect to create sound waves.

Answer 32

A coil of wire is wrapped around a permanent magnet.

An alternating current passes through the wire creating an electromagnetic field.

The magnetic field from the current and permanent magnetic interact causing a force of attraction or repulsion.

As the current is a.c. the force changes between attraction and repulsion.

This causes the loud speaker cone to vibrate which creates sound waves.