P1.3/4/5/6 - Generating Electricity/Global Warming

Question 1

Name three devices that use a direct current

Answer 1

Mobile phones, a laptop and an MP3 player

Question 2

Direct current is usually produced by __________.

Answer 2

Batteries

Question 3

Why is direct current only in one direction?

Answer 3

This is because the voltage from the battery remains the same throughout

Question 4

What type of electricity do we get from the mains?

Answer 4

AC

Question 5

How does an alternating current (AC) occur?

Answer 5

An alternating current happens because the voltage switches smoothly between positive and negative values. This means the current reverses direction very rapidly. The mains voltage in the UK is 230 V AC. The current changes direction 50 times every second.

Question 6

When is one cycle of alternating current completed?

Answer 6

One cycle of alternating current is completed when the current changes direction and then changes back again.

Question 7

In AC, what is the number of cycles per second called?

Answer 7

Frequency (Hz/Hertz)

Question 8

What is the frequency of the electricity supplied by the mains in the UK?

Answer 8

50 Hz (so this would be 50 cycles a second)

Question 9

How does moving a piece of wire between the poles of a magnet generate electricity?

Answer 9

Doing this creates, or induces, a voltage. An electric current then passes through the wire, giving a reading on a sensitive ammeter.

Question 10

What effect is it when we generate electricity using wires and a magnet?

Answer 10

The Dynamo Effect

Question 11

In terms of the Dynamo effect, the size of the current is increased if…

Answer 11

• Stronger magnets are used
• There are more turns of wire (making a coil)
• You move the wire faster

Question 12

How does a simple AC generator work?

Answer 12

It works by inducing a voltage between two magnets by rotating a coil of wire inside a magnetic field instead of moving through it.

Question 13

If an AC generator spins at 3000 rpm, how many rotations is this per second?

Answer 13

50 (That is nearly 50 times the output from your plug socket at home)

Question 14

What does induce mean?

Answer 14

To create

Question 15

How is electricity generated in the UK?

Answer 15

Electricity is generated using sources of energy. In the UK a great deal of electricity is generated by using an energy source to heat water. The energy source can be fossil fuels, nuclear or biomass. This type of station is called a thermal power station.

Question 16

How is energy wasted in a power station?

Answer 16

A significant amount of heat energy is transferred to the environment and is wasted.

Question 17

What equation can you use to work out the efficient of a power station?

Answer 17

Efficiency = useful energy output / total energy output (x100%)

Question 18

How is electricity we use in our homes distributed from power stations around the country?

Answer 18

The electricity you use is transmitted around the country by the National Grid. This is the mains supply that is available whenever you switch on an appliance at home.

Question 19

What are the names of two different types of electricity?

Answer 19

• Alternating Current (AC)

- Direct current (DC)