Topic 7; Magenetism And Electromagnetism

Question 1

What type of force is exerted when two like poles of a magnet are bought near each other?

Answer 1

Repulsive, non-contact

Question 2

What force is exerted when two unlike poles of a magnet are bought close together?

Answer 2

Attractive, non contact force

Question 3

What is the difference between a permanent and an induced magnet?

Answer 3

Permanent; produces own magnetic field

Induced; becomes magnetic when placed in magnetic field

Question 4

What type of force does induced magnetism always cause?

Answer 4

Force of attraction

Question 5

What happens when an induced magnet is moved away from the field?

Answer 5

It loses some/all of the magnetism

Question 6

What are 4 magnetic materials?

Answer 6

Cobalt
Nickel
Steel iron

Question 7

In what direction does a magnetic field point?

Answer 7

From the north seeking pole to the south seeking pole

In the direction a North Pole would experience if placed in the field

Question 8

What does a magnetic compass contain?

Answer 8

Small bar magnet pointing in the direction of the earth’s magnetic field

Question 9

What is produced when a current flows through a conducting wire?

Answer 9

Magnetic produced around wire

Question 10

What determines the strength of the magnetic field around the wire? (2)

Answer 10

1. Magnitude of the current flowing through

2. Distance from wire

Question 11

What is a solenoid?

Answer 11

Coil of wire creating a strong magnetic field when current passes thorugh

Question 12

Describe the magnetic field inside a solenoid

Answer 12

Strong and uniform

Question 13

What is an electromagnet?

Answer 13

Solenoid with an added iron core

-> adding iron core increases strength of magnetic field

Question 14

What is the motor effect?

Answer 14

When a force is exerted between a magnetic field and a current-carrying conductor in that field

Question 15

What rule is used to determine the force experienced due to the motor effect?

Answer 15

Fleming’s left hand rule

Question 16

What does the forefinger represent?

Answer 16

Direction of magnetic field

Question 17

What does the middle finger represent?

Answer 17

Points in direction of current flow in conductor

Question 18

What factors affect the size of the force on a current carrying wire in a magnetic field? (2)

Answer 18

1. Magnitude of current flowing through conductor

2. Strength of magnetic field the conductor is in

Question 19

If direction of current in current carrying wire placed in a uniform magnetic field is reversed, what happens to force?

Answer 19

Direction of force also reverses

Question 20

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

Answer 20

Strength of force is increased

Question 21

What is the criteria for the equation linking force, magnetic flux density, current and length to hold?

Answer 21

Conductor must be at right angles to field its placed in

Question 22

What is the unit for magnetic flux density?

Answer 22

Tesla, T

Question 23

How does an electric motor work?

Answer 23

• coil of wire with current placed in magnetic field
• forces on perpendicular sides to field experience forces in opposite directions
• causes rotational effect

Question 24

How do loudspeakers use the motor effect?

Answer 24

Converts variations in current of circuit into pressure variations- produce sound