P3

Question 1

What does neutral matter contain?

Answer 1

The same amount positive and negative particles

Question 2

What is static electricity?

Answer 2

The build-up of charge on objects

Question 3

When certain materials are rubbed together, what happens?

Answer 3

Negatively charged electrons will be taken from one object and given to the other
This will leave one object negatively charged, and the other positively charged

Question 4

What is the electric field?

Answer 4

The space surrounding any electric charge, in which its effects can be felt

Question 5

What happens when a charge is placed into the electric field of another charge?

Answer 5

The two electric fields interact, causing a force to be exerted on both charges

Question 6

Current can only flow round a closed circuit (True or False)

Answer 6

True

Question 7

What is the electrical current?

Answer 7

The rate of flow of electrical charge

Question 8

In a single, closed circuit, where is the current different at different point?

Answer 8

Nowhere, the current is the same all around the circuit

Question 9

What is the voltage?

Answer 9

The driving force that drives the current

Question 10

What is the resistance?

Answer 10

Anything that resists (slows) the flow of charge

Question 11

What does the term I-V characteristics refer to?

Answer 11

A graph that shows how the current flowing through a component changes as voltage changes
You can also use these graphs to work out the resistance at any point, using the equation V=IxR

Question 12

What happens in filament lamps?

Answer 12

As temperature increases due to more current flowing, resistance increases

Question 13

What happens in diodes?

Answer 13

Current can only flow in one direction (there is a very high resistance in one way)

Question 14

What is an LDR?

Answer 14

As light increases, resistance decreases and current increases

Question 15

What is a thermistor?

Answer 15

As temperature increases, resistance decreases and current increases

Question 16

In series circuits, what is the distribution of voltage?

Answer 16

Voltage is shared

Question 17

In series circuits, what is the distribution of current?

Answer 17

Current is the same everywhere

Question 18

In series circuits, what is the distribution of resistance?

Answer 18

Resistance adds up

Question 19

In parallel circuits, what is the distribution of voltage?

Answer 19

Voltage is the same on each branch, but then splits between each component on the branch

Question 20

In parallel circuits, what is the distribution of current?

Answer 20

Current is shared, but then stays the same for each component on the branch

Question 21

In parallel circuits, what is the distribution of resistance?

Answer 21

As more resistors are added, resistance decreases

Question 22

What does linear resistance mean?

Answer 22

The components have a constant resistance.

Question 23

What does non-linear mean?

Answer 23

The components have a changing resistance based on the current.

Question 24

What are magnetic fields?

Answer 24

Areas around a magnet in which other magnets or magnetic materials experience a force

Question 25

What does the closeness of the lines together in a magnetic field show?

Answer 25

How strong it is- the closer together the lines, the stronger the field

Question 26

How do compasses work?

Answer 26

They have a magnet within them, which always points north- this is because the Earth generates its own magnetic field

Question 27

What are permanent magnets?

Answer 27

Magnets that produce their own magnetic field

Question 28

What are induced magnets?

Answer 28

Magnetic materials that turn into magnets when placed in a magnetic field

Question 29

How can a magnetic field be induced, not using magnets?

Answer 29

When a current flows through a wire, a magnetic field is created around the wire

Question 30

What is a solenoid?

Answer 30

A coil of wire

Question 31

How can you increase the strength of the magnetic field produced by a current through a coil of wire?

Answer 31

You can increase the current or increase the number of turns in the coil while keeping the total length the same
You can also add a block of iron to the center of the coil, which will then become induced, increasing the magnetic field strength

Question 32

What is the motor effect?

Answer 32

When a current carrying wire is placed in a magnetic field of a magnet, causing a force to be exerted on the wire and the magnet

Question 33

How can you experience the full force of the motor effect?

Answer 33

The wire must be at 90 degrees to the magnetic field

Question 34

How can you change the direction of the force in the motor effect?

Answer 34

By changing the direction of the magnetic field or the current

Question 35

What is Fleming’s left hand rule?

Answer 35

Using your left hand:

• Point your first finger in the direction of the magnetic field
• With your second finger, point it in the direction of the current
• Your thumb will then point in the direction of the force

Question 36

What is electro-magnetic induction?

Answer 36

The induction of a voltage across a conductor which is experiencing a change in magnetic field

Question 37

What are the two situations where you get electro-magnetic induction?

Answer 37

1) If the magnetic field of an electrical conductor changes (size or reverses)
2) If an electrical conductor and a magnetic field move relative to each other (moving a magnet in a conductor or moving a conductor in a magnetic field

Question 38

How does a speaker work?

Answer 38

A loudspeaker contains a coil of wire which surrounds one pole of a permanent magnet
An current flows through the coil
Interactions between magnet cause movement which makes vibrations which creates sound
To sum up, electrical impulses are transformed into sound

Question 39

How does a microphone work?

Answer 39

The opposite of a speaker
A microphone contains a coil of wire which surrounds one pole of a permanent magnet
Sound waves hit diaphragm
Diaphragm vibrates causing movement
Movement of the coil creates current
To sum up, sound is transformed into electrical impulses

Question 40

What are transformers?

Answer 40

Devices that change the size of the potential difference in an alternating current
They contain a primary and secondary coil

Question 41

How can transformers make electricity transfer over distances more efficient (less energy dissapated as heat)?

Answer 41

As Power = Voltage x Current, to transmit huge amounts of power, you either need a large current or a large voltage- a large current will cause the wires to heat up, meaning more energy is lost. Therefore we must get a large voltage; by boosting the voltage very high, the current gets very low as the power must remain constant, so less energy is lost as the current is low.

Question 42

How do electric motors work?

Answer 42

• They convert electrical energy into mechanical energy using induction
• A simple electric motor can be built using a coil of wire that is free to rotate between two opposite magnetic poles. When an electric current flows through the coil, the coil experiences a force and moves
• The direction of the current must be reversed every half turn, otherwise the coil comes to a halt again. This is achieved using a conducting split ring commutator

Question 43

How do generators work?

Answer 43

• They convert mechanical energy into electrical
  energy
• They work by rotating a coil of wire in a magnetic field (between two magnets) or by rotating a magnet in a coil of wire. As the magnet or coil spins, an current is induced
• Slip rings at the end of the coil remain in contact with brushes that are connected to the rest of the circuit
• Alternating current

Question 44

What are dynamos?

Answer 44

Same as generators but have a split-ring commutator which swaps the connection every half turn to keep the current flowing in the same direction
- Direct current