Electricity

Question 1

What is current?

Answer 1

Flow of electrical charge.

Question 2

What is the unit for current?

Answer 2

Ampere, A.

Question 3

What is potential difference?

Answer 3

Driving force that pushes charge round.

Question 4

What is the unit for potential difference?

Answer 4

Volt, V.

Question 5

What is resistance?

Answer 5

Anything that slows down charge flow.

Question 6

What is the unit for resistance?

Answer 6

Ohm, Ω.

Question 7

What are the two factors that current through a component depend on?

Answer 7

> the component’s resistance.
↳ the greater the resistance, the smaller the current.
the potential difference across the component.
↳ the greater the potential difference, the larger the current (for a fixed resistance).

Question 8

What is the size of current the same as?

Answer 8

Rate of flow of charge.

Question 9

What is the formulae for charge flow?

Answer 9

Q = It
charge flow = current x time

[coulombs (C) = amps (A) x secs (S)]

Question 10

What is the formulae for potential difference?

Answer 10

V = IR
potential difference = current x resistance

[volts (V) = amps (A) x ohms (Ω)]

Question 11

Draw the circuit symbol of a cell.

Answer 11

Check your answer in your knowledge organiser (pg 83)

Question 12

Draw the circuit symbol of a battery.

Answer 12

Check your answer in your knowledge organiser (pg 83)

Question 13

Draw the circuit symbol of a open switch.

Answer 13

Check your answer in your knowledge organiser (pg 83)

Question 14

Draw the circuit symbol of a voltmeter.

Answer 14

Check your answer in your knowledge organiser (pg 83)

Question 15

Draw the circuit symbol of an ammeter.

Answer 15

Check your answer in your knowledge organiser (pg 83)

Question 16

Draw the circuit symbol of a closed switch.

Answer 16

Check your answer in your knowledge organiser (pg 83)

Question 17

Draw the circuit symbol of a resistor.

Answer 17

Check your answer in your knowledge organiser (pg 83)

Question 18

Draw the circuit symbol of a variable resistor.

Answer 18

Check your answer in your knowledge organiser (pg 83)

Question 19

Draw the circuit symbol of a filament lamp (or bulb).

Answer 19

Check your answer in your knowledge organiser (pg 83)

Question 20

Draw the circuit symbol of a diode.

Answer 20

Check your answer in your knowledge organiser (pg 83)

Question 21

Draw the circuit symbol of a LDR.

Answer 21

Check your answer in your knowledge organiser (pg 83)

Question 22

What does LDR stand for?

Answer 22

Light-dependent resistor.

Question 23

Draw the circuit symbol of a thermistor.

Answer 23

Check your answer in your knowledge organiser (pg 83)

Question 24

Draw the circuit symbol of a LED.

Answer 24

Check your answer in your knowledge organiser (pg 83)

Question 25

What does LED stand for?

Answer 25

Light-emitting diode.

Question 26

Draw the circuit symbol for fuse.

Answer 26

Check your answer in your knowledge organiser (pg 83)

Question 27

What do the straight lines connecting the components represent?

Answer 27

Wires.

Question 28

What are the three different current devices?

Answer 28

> ohmic conductor such as a resistor at constant temperature. > filament lamp. > diode.

Question 29

What happens to the resistance in a ohmic conductor?

Answer 29

It doesn't change as current is directly proportional to potential difference.

Question 30

Is a ohmic conductor's graph linear or non-linear?

Answer 30

Linear.

Question 31

What happens to the resistance in a filament lamp?

Answer 31

The resistance increases as the temperature of filament increases due to the current increasing.

Question 32

Is the filament lamp graph linear or non-linear?

Answer 32

Non-linear.

Question 33

What happens to the resistance in a diode?

Answer 33

The resistance is high in one direction so the current only flows in the other direction.

Question 34

Is the diode graph linear or non-linear?

Answer 34

Non-linear.

Question 35

Draw the graph of a ohmic conductor.

Answer 35

Check your answer in your knowledge organiser (pg 84)

Question 36

Draw the graph of a filament lamp.

Answer 36

Check your answer in your knowledge organiser (pg 84)

Question 37

Draw the graph for a diode.

Answer 37

Check your answer in your knowledge organiser (pg 84)

Question 38

What components have changing resistance (when current though them varies)?

Answer 38

> filament lamp (or bulb). > diode. > LDR. > thermistor.

Question 39

When using an LDR, what does the resistance depend on?

Answer 39

Light intensity.

Question 40

When using an LDR, there is lower resistance in...

Answer 40

...brighter light.

Question 41

What is LDR used in?

Answer 41

Automatic night lights.

Question 42

When using a thermistor, resistance depends on?

Answer 42

Temperature.

Question 43

When using a thermistor, there is lower resistance in...

Answer 43

...hotter temperatures.

Question 44

What can you find a thermistor in?

Answer 44

Thermostats.

Question 45

Explain what happens in a series circuit.

Answer 45

> current is the same everywhere. ↳ I₁ - I₂ > total source potential difference is shared between components. ↳ (total) V = V₁ + V₂ > Total resistance of components = sum of their resistances. ↳ (total) R = R₁ + R₂ > adding a resistor in a series circuit increases the total resistance of the circuit.

Question 46

Explain what happens in a parallel circuit.

Answer 46

> total current flowing around a circuit = sum of the currents through each branch. ↳ (total) I = I₁ + I₂ > potential difference across each branch in the same as the source potential difference. ↳ V₁ = V₂ = V (total) > adding a resistor in a parallel circuit decreases the total resistance of the circuit.

Question 47

What does AC stand for?

Answer 47

Alternating current.

Question 48

What is alternating current?

Answer 48

Current that constantly changes direction and is produced by an alternating voltage. [used in mains supply]

Question 49

What does DC stand for?

Answer 49

Direct current.

Question 50

What is direct current?

Answer 50

Current that always flows in the small direction and is produced by a direct voltage. [supplied by batteries]

Question 51

What are three facts about the UK mains?

Answer 51

> ac supply. > frequency of 50 Hz. > voltage around 230 V.

Question 52

What are the three wires in a three-core cable called?

Answer 52

> live wire. > neutral wire. > earth wire.

Question 53

Describe the live wire.

Answer 53

> brown. > potential difference is at 230 V. > it is used to provide alternating potential difference from mains supply.

Question 54

Describe the neutral wire.

Answer 54

> blue. > potential difference is at around 0 V. > it is used to complete the curcuit.

Question 55

Describe the earth wire.

Answer 55

> green and yellow. > potential difference is at 0 V. > it is used to stop appliance casing becoming live.

Question 56

What happens when a body is electrocuted?

Answer 56

① the body has 0V whilst a wire can hold 230V. ② ones touched, large potential difference is produced across the body. ③ Curren flows through the body.

Question 57

What are the two formulaes for energy transferred?

Answer 57

E = QV energy transferred = charge flow x potential difference [joules (J) = current (C) x voltage (V)] OR E = Pt energy transferred = power x time [joules (J) = watts (W) x secs (S)]

Question 58

What does the amount of energy an appliance transfers depend on?

Answer 58

> appliance's power. | > how long appliance is on for.

Question 59

What is power?

Answer 59

Energy transferred per second.

Question 60

What is power rating?

Answer 60

The maximum safe power an appliance can operate at.

Question 61

What are the two formulaes for power?

Answer 61

``` P = VI power = potential difference x current ``` [watts (W) = voltage (V) x amps (A)] OR ``` P = I²R power = current² x resistance ``` [watts (W) = amps (A)² x ohms (Ω)