Physics Triple 2

Question 1

What is a transformer?

Answer 1

An electrical device used to change alternating voltage

Question 2

What is a electromagnet?

Answer 2

A magnet whose field can be turned of and on with an electric current

Question 3

What is electromagnetic induction?

Answer 3

The process of inducing a potential difference in a wire by moving the wire so it cuts across the lines of a magnetic field

Question 4

What is a magnetic field?

Answer 4

A magnetic field is a region where magnets such as iron and steel plus wires carrying current experience a force acting upon them

Question 5

How does a dynamo work?

Answer 5

Cog wheel at the top is positioned so it touches one of the wheels as wheel moves round it turns the cog which is attached to the magnet this creates an AC current to power the light

Question 6

What are the advantages of a dynamo?

Answer 6

No batteries so they wont run out

Renewable so doesn’t require electrical energy

Question 7

What are the disadvantages of a dynamo?

Answer 7

Have to pedal

Not instant

Question 8

What does flemings left hand rule tell us?

Answer 8

Which way the force acts

Question 9

How do you change the direction of a force?

Answer 9

Reverse magnetic current or change magnetic field

Question 10

How do you increase the size of a force?

Answer 10

Increase current and magnet strength
- size depends on the angle between the wire and field lines
Its at its greatest when its perpendicular to the field lines

Question 11

Why do transformers only work on AC?

Answer 11

AC changes the direction of the magnetic field consistently and to induce a secondary coil there needs to be a changing magnetic field

Question 12

How does a transformer work?

Answer 12

The current flows through the primary coil this creates a magnetic field, the current alternates so the magnetic field in the iron core is consistently changing. The rapidly changing magnetic field is felt by the secondary coil and the changing field induces an alternating PD across the secondary coil

Question 13

What is the difference between switch mode and and normal transformer?

Answer 13

Lighter
Higher frequency
More efficient as it has a lower power supply and doesn’t have a load applied

Question 14

What is a switch mode transformer used for?

Answer 14

Mobile phone chargers

Laptop chargers

Question 15

How do you speed up electric motors?

Answer 15

More current

Increase strength of magnetic field

Question 16

What does a spindle do?

Answer 16

Rotates coil

One force acts up the other acts down

Question 17

What does a split ring commutator do?

Answer 17

Swaps contact every half turn to keep motor rotating in same direction

Question 18

How can the direction of the motor be reversed?

Answer 18

Swapping polarity of DC supply

Swapping magnetic poles over

Question 19

Why is an electromagnet useful?

Answer 19

Its useful as you can switch the current off and on and therefore turn the magnet on and off

Question 20

How do you induce a magnet?

Answer 20

Moving a magnet in a coil wire

Turning a magnet end to end in a coil wire

Question 21

How do you reverse current in electromagnetic induction?

Answer 21

Move magnet in opposite direction

Question 22

What is the motor effect?

Answer 22

The force experienced by a current carrying wire in a magnetic field

Question 23

How do you increase the size of induced current?

Answer 23

Increase the speed at which the coil rotates
Increase strength of magnetic field
Increase number of turns in the coil and increase total area of the coil

Question 24

How does an electric motor work?

Answer 24

1. Electric motor is turned on
2. Current flows through the coil
3. Flowing electron create a magnetic field
4. The magnetic field of wire and magnet interact
5. Equal and opposite forces experienced on each side
6. Coil rotates half turns
7. Momentum of coil pushes beyond half turn
8. Split ring commutator ensures current remains on the same side
9. Carbon brushes stop tangling
10. Coil rotates another half turn and so on until it is switched off

Question 25

Why does it have a iron core?

Answer 25

The iron core is purely for transferring the changing magnetic field from the primary coil to the secondary coil
- no electricity flows around the coil