Physics Electricity

Question 1

What is the unit of electric current?

Answer 1

Ampere (A)

Question 2

What is the unit of electric charge?

Answer 2

Coulomb (C)

Question 3

What is the unit of energy transferred?

Answer 3

Joule (J)

Question 4

What is the unit of resistance?

Answer 4

Ohm (Ω)

Question 5

What is the unit of time?

Answer 5

Second (s)

Question 6

What is the unit of potential difference?

Answer 6

Volt (V)

Question 7

What is the unit of power?

Answer 7

Watt (W)

Question 8

What is mains electricity?

Answer 8

Electricity supplied to homes as alternating current (a.c.)

Question 9

What type of current is supplied by a battery?

Answer 9

Direct current (d.c.)

Question 10

Why is insulation used on wires?

Answer 10

To prevent electric shocks by stopping current leaving the wire

Question 11

What is double insulation?

Answer 11

Two layers of insulation so no metal parts can become live

Question 12

Why is earthing used?

Answer 12

To provide a safe path for current if a fault occurs

Question 13

What does a fuse do?

Answer 13

Melts and breaks the circuit if current is too large

Question 14

What does a circuit breaker do?

Answer 14

Automatically switches off if current becomes too large

Question 15

Why does a current in a resistor increase temperature?

Answer 15

Electrical energy is transferred to thermal energy

Question 16

Give a domestic use of heating by resistance.

Answer 16

Kettles toasters heaters irons

Question 17

State the equation linking power current and voltage

Answer 17

P = I × V

Question 18

How is the power equation used to choose a fuse?

Answer 18

Fuse rating should be just above normal operating current

Question 19

State the equation for energy transferred by a current

Answer 19

E = I × V × t

Question 20

Why are parallel circuits used in homes?

Answer 20

Each appliance gets the same voltage and works independently

Question 21

Why are series circuits unsuitable for homes?

Answer 21

If one component fails all stop working

Question 22

How does current behave in a series circuit?

Answer 22

The current is the same everywhere

Question 23

How does voltage behave in a series circuit?

Answer 23

Voltage is shared between components

Question 24

How does voltage behave in a parallel circuit?

Answer 24

Voltage across each branch is the same

Question 25

Describe current voltage behaviour in a resistor

Answer 25

Current is proportional to voltage

Question 26

Describe current voltage behaviour in a filament lamp

Answer 26

Resistance increases as temperature increases

Question 27

Describe current voltage behaviour in a diode

Answer 27

Current flows in one direction only after threshold voltage

Question 28

How can current voltage relationships be investigated?

Answer 28

By measuring current and voltage and plotting a graph

Question 29

What happens to current if resistance increases?

Answer 29

Current decreases

Question 30

How does resistance of an LDR change with light?

Answer 30

Resistance decreases as light increases

Question 31

How does resistance of a thermistor change with temperature?

Answer 31

Resistance decreases as temperature increases

Question 32

How can lamps or LEDs be used in circuits?

Answer 32

To indicate the presence of current

Question 33

State the equation linking voltage current and resistance

Answer 33

V = I × R

Question 34

What is electric current?

Answer 34

The rate of flow of charge

Question 35

State the equation linking charge current and time

Answer 35

Q = I × t

Question 36

What charge carriers move in metals?

Answer 36

Negatively charged electrons

Question 37

Why is current conserved at a junction?

Answer 37

Charge cannot be lost

Question 38

What happens to current at a junction?

Answer 38

It splits between branches

Question 39

How do you calculate total resistance in series?

Answer 39

Add the resistances

Question 40

What does voltage measure?

Answer 40

Energy transferred per unit charge

Question 41

What is one volt equal to?

Answer 41

One joule per coulomb

Question 42

State the equation linking energy charge and voltage

Answer 42

E = Q × V