Electromagnetism

Question 1

What do unlike and like poles do?

Answer 1

Unlike attract and like repel

Question 2

Lines of magnetic field can be plotted using what?

Answer 2

A compass

Question 3

A magnet that has a N and S pole all the time is called a what magnet?

Answer 3

A permanent magnet

Question 4

What materials are magnetic?

Answer 4

Iron,steel,cobalt and nickel

Question 5

What is the magnetic field?

Answer 5

The region around a magnet where a force acts on another magnet or magnetic material.

Question 6

What does the thumb indicate on the thumb rule?

Answer 6

The direction of the current

Question 7

What do the fingers represent for the thumb rule?

Answer 7

The direction of the magnetic field.

Question 8

What is force measured in?

Answer 8

Newtons

Question 9

What does polarity mean?

Answer 9

The poles of the magnet.

Question 10

What happens to the field around a solenoid?

Answer 10

As the current increases so does the strength of the magnetic field (Paper clip experiment)

Question 11

What are the two types of magnet?

Answer 11

Permanent or induced magnets

Question 12

What do step-up transformers do?

Answer 12

Increase the potential difference

Question 13

What do step-down transformers do?

Answer 13

Decrease the potential difference

Question 14

What is different about the step-up and step-down transformers?

Answer 14

Step-up transformers have more turns on the secondary coil whereas step-down transformers have more turns on the primary coil.

Question 15

What is the Transformer equation?

Answer 15

Vp/Vs = np/ns

^input pd/output pd=no. turns on primary/no. secondary

Question 16

What can be said about the efficiency of transformers

Answer 16

They are almost 100% efficient

Question 17

Why do transformers only work for Ac?

Answer 17

Because we need a changing magnetic field to induce a potential difference.

Question 18

What is The National Grid?

Answer 18

A system of transformers and high voltage cables that distribute energy to peoples homes

Question 19

What is the main problem when getting electricity to homes?

Answer 19

Energy is always lost in the power cables due to the resistance of the wires

Question 20

What can you say about the amount of energy lost depending on the distance away from the national grid?

Answer 20

The further travelled, the more energy lost.

Question 21

What, other than using transformers, will reduce energy loss?

Answer 21

Having power stations closer to homes.

Question 22

Describe the first stage how energy gets to peoples homes.

Answer 22

First electricity from the power station passes through step up transformer which increase the potential difference to 100’s of thousands of volts.

Question 23

Describe the second stage of energy getting to homes

Answer 23

Less energy is lost through the power cables when pd is high hence the step-up transformer.

Question 24

Describe the final stage of getting energy to homes

Answer 24

Electricity then passes through the step-down transformer as the pd is far too high so it reduces it to 230V.