Generating electricity

Question 1

What is a magnetic field?

Answer 1

A region where magnetic materials and also wires carrying currents experience a force acting on them

Question 2

Where do the arrows go from in a magnet diagram?

Answer 2

From the North Pole to the South Pole

Question 3

What is the shape of the magnetic field of a straight current-carrying wire?

Answer 3

The field is made up of concentric circles with the wire in the centre

Question 4

Why are wire coils more reinforced in magnetic fields?

Answer 4

Because the two magnetic fields of the wires meet in the middle, reinforcing both fields

If there were many coils many fields would meet and reinforce, making it more sturdy

Question 5

Is the magnetic field strong or weak in a coil of wire?

Answer 5

Strong and uniform, running the length of the coil

Question 6

What is the magnetic field like outside a coil?

Answer 6

Like a bar magnet

Question 7

What happens to the magnetic field if the current is reversed in a coil?

Answer 7

The north and south swap ends

Question 8

How can you increase the strength of the magnetic field around a coil (solenoid)?

Answer 8

Adding a magnetically ‘soft’ iron core though the middle of the coil

This turns it into an electromagnet

Question 9

What is a magnetically soft material?

Answer 9

A material that magnetised and demagnetises easily so as soon as you turn off the current through the solenoid (coil) the magnetic field disappears

Question 10

What happens when you put a current carrying wire between magnetic poles?

Answer 10

The two magnetic fields affect one another and a force on the wire is made

Question 11

What is the force if a current carrying wire runs along the magnetic field lines?

Answer 11

Nothing, as it does not break any magnetic field lines.

Question 12

Is the force strong or weak when a current carrying wire is 90 degrees to a magnetic field?

Answer 12

It is at its fullest

Question 13

What direction does the force travel on a current carrying wire in a magnetic field?

Answer 13

The same direction relative to the magnetic field of the magnets and the direction of the current in the wire (Left hand rule)

Question 14

How do you find the way the force acts on a current carrying wire in a magnetic field?

Answer 14

Using the left hand rule

thuMb - Motion
First finger - Force of magnet
seCond finger - Direction of conventional current

Question 15

What speeds up an electric motor?

Answer 15

More current
More turns on the coil
Stronger magnetic field
A soft iron core in the coil

Question 16

How does an electric motor work?

Answer 16

A coil is on a spindle and has a current running through it with a magnetic field

One force goes up and one goes down, making the coil spin

The coil swaps the contacts every half a turn to keep the motor rotating in the same direction

Question 17

How can the direction of a motor be reversed?

Answer 17

By swapping the polarity of the electricity supply or swapping the magnetic poles

Question 18

What do practical motors (Eg a drill) have instead of simple electrical motors to generate electricity?

Answer 18

They have pole pieces which are so curved they form a hollow cylinder. The coil spins inside the cylinder.

They stick anything to the end of the pole and it spins

Question 19

How do AC generators work?

Answer 19

Use a turbine to rotate a coil in a magnetic field (like a motor)

As the coil spins a current is induced in the coil. This current changes direction every half turn

Instead of a split-ring communicator, they have slip rings and brushes so the contacts don’t spin every half turn

This means they produce AC voltage

Question 20

How do Dynamo generators work?

Answer 20

They rotate the magnet instead of the coil

This causes the field through the coil to swap every half turn also, so the output is the same as a normal generator

Question 21

Why do you need transformers in power lines?

Answer 21

Without them, the current in the wire would be high and energy would be lost through heat.
However, large voltage means small current, so it’s boosted up to 400,000V to prevent energy loss

Question 22

What is an isolating transformer?

Answer 22

A transformer that is equal on both sides, and reduces mains electricity for safety

Question 23

How does an isolating transformer protect you?

Answer 23

It makes it so you’re not directly touching the mains so there’s no way current can flow through you

Question 24

How do nuclear power stations work?

Answer 24

Uranium atoms are split, generating loads of heat which power a turbine

Question 25

What is nuclear fusion?

Answer 25

Two nuclei combine to create a larger nucleus

Question 26

Why are people trying to create fusion reactors?

Answer 26

Fusion creates the most energy

Question 27

What are the challenges for fusion reactors?

Answer 27

It needs to be really hot and nearly no material can withstand the heat