Year 7 Megnetism and Electricity

Question 1

What metals are magnetic?

Answer 1

Iron, nickel, cobalt and alloys containing the three

Question 2

Where is the magnetic field of an object strongest?

Answer 2

At the poles

Question 3

How do compasses work?

Answer 3

The Earth has an outer core of liquid iron an nickel which is magnetic, and a compass is a magnet in a liquid so it can rotate towards a pole

Question 4

What is the electric current?

Answer 4

The flow of electrons going round

Question 5

What is needed to form an electrical circuit?

Answer 5

A complete circuit and a voltage

Question 6

List the similarities and differences between magnetic force and electric charge

Answer 6

Similarities: same poles repel, different poles attract, both have poles, field is strongest at poles
Differences: you can have just a north or south pole in electric charge, but in magnets you have to have both poles

Question 7

What is charging by induction?

Answer 7

E.g. A negatively charged rod is placed near a neutral object. The excess electrons in the rod repel the electrons in the object making them move as far away from the rod as possible. This shifting of electrons makes one side of the object positive and the other side negative. However, the object is still neutral

Question 8

Why does your hair stick to balloons?

Answer 8

When you rub a balloon against your hair some of the electrons get transferred from your hair to the balloon. This makes the balloon negatively charged and leaves your hair positively charged. Since opposite poles attract, your hair will be attracted to the balloon

Question 9

What are the three things needed to make an electromagnet work?

Answer 9

Coils, a core and a current

Question 10

Why do Van Der Graaf generators cause aluminium cases to fly off?

Answer 10

The belt turns and electrons rub off onto the dome. Some of these electrons go onto the cases, so both the dome and the cases are positively charged. Since similar charges repel, the cases fly off

Question 11

How is electricity generated in a coal power plant?

Answer 11

1. The coal is burned to boil water to make steam
2. The steam makes a turbine spin
3. The spinning turbine turns a generator which produces power
4. The energy goes through a translator to be used by people