P2 Electricity

Question 1

What is electricity?

Answer 1

The flow of charge of electrons.

Question 2

How does current flow?

Answer 2

Positive to negative.

Question 3

What is the unit for charge?

Answer 3

Coulombs (C).

Question 4

What is potential difference?

Answer 4

The measure of how much energy is transferred to/by each Coulomb of charge.

Question 5

What is the unit for PD?

Answer 5

Volt (V).

Question 6

How are voltmeters placed in a circuit?

Answer 6

In parallel.

Question 7

How are ammeters placed in a circuit?

Answer 7

In series.

Question 8

What is current?

Answer 8

The rate of flow of charge.

Question 9

What is the units for current?

Answer 9

Amps/Amperes (A).

Question 10

What is resistance?

Answer 10

The measure of how much a component/object resists the flow of current.

Question 11

What are the units of resistance?

Answer 11

Ohms.

Question 12

What is the relationship between Current and PD with fixed resistors?

Answer 12

Directly proportional.

Question 13

What is the relationship between current and pd with a filament lamp?

Answer 13

larger current = increased resistance.

Question 14

What is the relationship between current and pd with a diode?

Answer 14

current flows in one direction. Low resistance in forward direction, high resistance in reverse direction.

Question 15

Characteristics for series circuits.

Answer 15

Total PD is shared between all components
current is the same for all components
total resistance = sum of resistances.

Question 16

Characteristics for parallel circuits.

Answer 16

PD for each branch = PD of cell/battery
current is split between branches
adding more resistors in parallel reduces total resistance.

Question 17

What is a thermistor?

Answer 17

A thermistor can detect changes in temperature. If the temp increases, the resistance of the thermistor decreases.

Question 18

What is a light dependent resistor?

Answer 18

An LDR can detect changes in light. If light intensity increases, resistance decreases.

Question 19

What is DC?

Answer 19

Direct current. Current that only flows in one direction.

Question 20

What is AC?

Answer 20

Alternating current. Current that flows in both directions.

Question 21

What is the UK mains voltage?

Answer 21

230V

Question 22

Which wire is the brown wire?

Answer 22

The live wire.

Question 23

Which wire is the blue wire?

Answer 23

The neutral wire.

Question 24

What is the yellow and green wire?

Answer 24

The earth wire - safety feature.

Question 25

What is a fuse?

Answer 25

A thin metal wire in a tube that is designed to melt or ‘blow’ if there is a fault that causes a high current. They are usually 3A, 5A or 13A.

Question 26

What is the national grid?

Answer 26

A mixture of power stations, cables and more which transmit power across a country.

Question 27

What is a step-up transformer?

Answer 27

Increases the voltage to around 132kV, which decreases the current, reducing the power lost due to heating the cables.

Question 28

What is a step-down transformer?

Answer 28

Reduces the voltage down to a safer and usable 230V for homes and businesses.