Section 6 Magnetism And Electromagnetism

Question 1

What is solenoid

Answer 1

Current carrying wire wrapped into a coil

Question 2

How a relay makes use of an electromagnet

Answer 2

When the electromagnet is switched on it attracts an iron contact attached to a rocker the rocker pivots pushing contacts together which completes a second circuit abs switches it on

Question 3

Name some magnetic materials

Answer 3

Iron steel nickel or cobalt

Question 4

Name non magnetic material

Answer 4

Rubber glass wood and plastic

Question 5

Non magnetic material

Answer 5

Rubber glass wood platic

Question 6

What creates a magnetic field

Answer 6

A moving charge
When a current flows through a conductor

Question 7

Advantage of electromagnets

Answer 7

Turns on and off quickly
A lot stronger than permanent magnets

Question 8

How are permanent and electromagnets used differently

Answer 8

Permanent magnets always produce a magnetic so they don’t need a current
They generate electricity and put information in the magnetic strip of a credit card

Question 9

What is an electromagnet

Answer 9

Is a solenoid with a soft iron core

Question 10

What are iron fillings

Answer 10

They show magnetic fields
Very small pieces of iron

Question 11

What does reversing the direction of the current do

Answer 11

Reverses the direction of the force

Question 12

What does reversing the direction of the Magnetic field do

Answer 12

Reverses the direction of force

Question 13

Flemings left hand rule tells you what

Answer 13

The way force acts
Thumb - motion
First finger - field
Second finger - current

Question 14

How do loud speakers work

Answer 14

Motor effect
The alternating current produces a changing magnetic field around the coil

Question 15

How is the turning effect on a Coil increased

Answer 15

Increasing the current in the coil
Increasing the number of turns on the coil
Increasing the strength of the magnetic field

Question 16

What is a fc motor

Answer 16

Made from A coil of wire in a magnetic field

Question 17

What does a ac generator do

Answer 17

Turn a coil when there’s a current

Question 18

What is a direct current

Answer 18

A current that always flows in the same direction

Question 19

What is a alternating current

Answer 19

A current that constantly changes direction

Question 20

Why are skip rings used

Answer 20

So that contacts don’t swap every half turn of the coil

Question 21

What do transformers do

Answer 21

Change the voltage of alternating currents

Question 22

Transformer equation

Answer 22

Number of turns in primary coil/number of turns on secondary coil

Question 23

How is electricity transmitted

Answer 23

At a high voltage from power stations to consumers

Question 24

Potential difference across the transformers primary coil

Answer 24

Primary current x voltage = secondary current x secondary voltage

Question 25

What is meant by electromagnetic induction

Answer 25

The creation of an emf in a conductor which is experiencing a change in a magnetic field

Question 26

Do step up transformers have more turns on their primary or secondary coil

Answer 26

The secondary coil

Question 27

Explain how step up and step down transformers are used in the transmission of electricity from power stations to consumers

Answer 27

A step up transformer is used to increase the voltage of electricity supplied by the power stations for transmission through cables

Step down transformers are then used to bring the voltage of the supply back down to a safe level to be supplied to a consumer

Question 28

Why transmitting electricity is more efficient when it is transmitted at a high voltage

Answer 28

Transmitting electricity at a high voltage means transmitting at a low current because p= IV
The power loss in a wire due to heating

The equation Shows that the power loss is lower when the current is lower so transmisssers no is more efficient when the wire has a lower current and therefore a higher voltage