Circuits

Question 1

How is static electricity achieved?

Answer 1

By rubbing certain insulating materials together, transferring electrons from one to the other, which leaves a positive static charge on one and a negative static charge on the other
-e.g. polythene rod and duster, balloon and jumper

Question 2

Which charges repel and which attract?

Answer 2

• Like charges repel

- Opposite charges attract

Question 3

What can charges move easily through?

Answer 3

Conductors

Question 4

What is current?

Answer 4

Flow of electrical charge around a circuit

Question 5

When does current only flow?

Answer 5

When there is potential difference

Question 6

What is potential difference?

Answer 6

Driving force that pushes current round the circuit (work done per unit of charge)

Question 7

What is resistance?

Answer 7

Anything in the circuit which slows the flow down

Question 8

What effect does temperature have on resistance?

Answer 8

It increases with temperature as heat causes ions to vibrate more so they get in the way of the electrons more making it harder for current to flow

Question 9

Why do resistors have a limit of current that can flow through?

Answer 9

Becasuse an increase in current increases temperature, which increases resistance, so current decreases again

Question 10

How must an ammeter and voltmeter be connected to a circuit?

Answer 10

• Ammeter must be connected in series

- Voltmeter must be connected in parallel

Question 11

What is a diode, what is it made from, and what is it used for?

Answer 11

• Only allows current to flow in one direction
• Made from a semiconductor such as silicon
• Used to regulate potential difference

Question 12

What is a light-emitting diode and what is it used for?

Answer 12

• Emits light when current flows through in the forward direction
• Used to show an appliance is switched on

Question 13

Why is a light-emitting diode (LED) better than other forms of lighting and where is it being used?

Answer 13

-Uses smaller current so is being used more in traffic lights, remote controls and digital clocks

Question 14

What is a light-dependent resistor and where is it used?

Answer 14

• Resistor dependent on intensity of light
• As light intensity increases, resistance decreases
• Used in streetlights and burglar detectors

Question 15

What is a thermistor and where is it used?

Answer 15

• Resistor dependent on temperature
• As temperature increases, resistance decreases
• Used in temperature detectors e.g. thermostats

Question 16

What is a series circuit and where are they used?

Answer 16

• Components connected in a line (except voltmeter)

- e.g. fairy lights

Question 17

What happens if one component is removed from a series circuit?

Answer 17

The circuit is broken and all components stop

Question 18

What happens to potential difference in a series circuit?

Answer 18

Potential difference is shared and equals source voltage

Question 19

What happens to current in a series circuit?

Answer 19

Current is the same everywhere in the circuit

Question 20

What happens to resistance in a series circuit?

Answer 20

Total resistance is the sum of all resistance in the circuit

Question 21

What is a parallel circuit and where are they used?

Answer 21

• Each component is separately connected to the supply

- e.g. everything electrical in a car

Question 22

What happens if one component is removed from a parallel circuit?

Answer 22

Removing one component hardly affects the others

Question 23

What happens to potential difference in a parallel circuit?

Answer 23

Potential difference is the same across all branches; they all get the full source voltage

Question 24

What happens to current in a parallel circuit?

Answer 24

Current is shared between the branches and equals total current. It splits and rejoins at junctions

Question 25

What is shown on a potential difference-current graph for resistors?

Answer 25

Current is directly proportional to potential difference, but different resistors have different resistances, so they will have different slopes

Question 26

What is shown on a potential difference-current graph for filament bulbs?

Answer 26

As the temperature of the filament increases, resistance increases, so the graph curves more as it moves away from the origin in both directions

Question 27

What is shown on a potential difference-current graph for diodes

Answer 27

Current will only flow in one direction so the line is only in the positive current section of the graph