Electromagnetism

Question 1

What direction does magnetic field always travel

Answer 1

North to South

Question 2

What does the spacing between magnetic field lines show

Answer 2

The strength of the magnetic field

Question 3

What magnetic field does a wire produce

Answer 3

a circular magnetic field

Question 4

what magnetic field does a solenoid produce

Answer 4

one similar to a bar magnet. But the direction depends on the direction of current.

Question 5

what happens to magnetic field when current is decreased through a wire

Answer 5

it decreases

Question 6

What does the thumb represent in Fleming’s left hand rule

Answer 6

Motion (force)

Question 7

What does the first finger represent in Fleming’s left hand rule

Answer 7

magnetic field

Question 8

What does the second finger represent in Fleming’s left hand rule

Answer 8

current

Question 9

What is the equation for Force in a generator

Answer 9

F = IBL
force(N) = current(A) x magnetic field(T) x length of wire(m)

Question 10

What does B represent in physics

Answer 10

Magnetic flux density (Tesla)

Question 11

What does L represent in physics - magnetism

Answer 11

Length of the wire (metres)

Question 12

What is force measured in

Answer 12

Newtons

Question 13

How can force be increased in a motor(3)

Answer 13

• increase the current
• increase the length of the wire
• increase the magnetic field

Question 14

How do you increase the magnetism of a solenoid

Answer 14

Increase the number of turns/coils

Question 15

What device uses the motor effect

Answer 15

Electric motors

Question 16

What is electromagnetic induction

Answer 16

Inducing a current by cutting magnetic field lines with a wire/coil

Question 17

If you move a wire parallel through a magnetic field will a current be produced

Answer 17

No

Question 18

If you move a wire so that it cuts through a magnetic field will it produce current

Answer 18

Yes

Question 19

How can you increase size of the current produced when generating electricity with a straight wire (3)

Answer 19

• increase the strength of the magnetic field
• increase the speed of the movement
• increase the length of wire within the magnetic field

Question 20

Which hand is used for motors

Answer 20

Left

Question 21

Which hand is used for generators

Answer 21

Right

Question 22

How can induced current be increased in a generator (5)

Answer 22

• increase strength of the magnetic field
• increase the speed of rotation
• add more turns to the coil
• use a coil with a larger area
• adding an iron core to the coil

Question 23

What type of current is induced from a generator

Answer 23

A.C.

Question 24

What happens to voltage when the magnetic field is twice as strong in a generator

Answer 24

It doubles

Question 25

What happens to voltage when the coil is spun twice as fast in a generator

Answer 25

• it doubles
• each half revolution is twice as fast

Question 26

What do split rings do

Answer 26

Rotate with the coil

Question 27

What do carbon brushes do

Answer 27

Maintain constant contact with the slip rings to transfer current to the external circuit

Question 28

How is a current induced in the secondary coil of a transformer (3)

Answer 28

The alternating current in the primary coil produces an alternating magnetic field. This cuts through the secondary coil, inducing an alternating current.

Question 29

Why are soft iron cores in transformers laminated

Answer 29

The magnetic field causes them to heat. This wastes energy and is less efficient. Laminations reduce heat loss.

Question 30

What two coils are involved in a transformer

Answer 30

Primary and Secondary coils