Electricity And Circuits

Question 1

What does an ammeter measure

Answer 1

Current

Question 2

What does a voltmeter measure

Answer 2

Potential difference (voltage)

Question 3

What is electric current (I)

Answer 3

The amount of electricity flowing through a circuit per second

Question 4

What is electric current measured in

Answer 4

Amps (A)

Question 5

What is potential difference/voltage

Answer 5

Energy per unit of charge that is transferred by a component

Question 6

Must ammeters be wired in series or in parallel

Answer 6

Series

Question 7

What is the current rule

Answer 7

The total current into a junction must equal the total current out of the junction

Question 8

Must voltmeters be wired in series or in parallel

Answer 8

In parallel

Question 9

What is the Volt rule

Answer 9

Total potential difference over everything in each loop equals the potential difference over the supply

Question 10

Current =

Answer 10

Charge divided by time

Question 11

Energy transferred =

Answer 11

Charge x potential difference

Question 12

Charge =

Answer 12

Current x time

Question 13

Potential difference =

Answer 13

Current x resistance

Question 14

What is resistance measured in

Answer 14

Ohms Ω

Question 15

Why do resistors transfer heat

Answer 15

Because the electrons collide with the ions in the lattice of the material

Question 16

How do you reduce the energy transfer coming out of a wire

Answer 16

Cool the wire
use low resistance wire
make the wires thicker
make the wires as short as possible

Question 17

Energy transferred =

Answer 17

Current x potential difference x time

Question 18

What is power measured in

Answer 18

Watts W

Question 19

Electrical power =

Answer 19

Current (squared) x resistance

Question 20

What happens in a direct current

Answer 20

Voltage is always constant and electricity flows in a certain direction

Question 21

What happens in an alternating current

Answer 21

Voltage changes from neg to pos and pos to neg.
Direction also changes 

Question 22

Do cells and batteries supply direct or alternating current

Answer 22

Direct

Question 23

Describe the UK domestic supply

Answer 23

Alternating current
Frequency of 50 Hz
Voltage of 230V

Question 24

What does the live wire do

Answer 24

Carries the current which enters the device

Question 25

What does the neutral wire do

Answer 25

Connects to the cable in the wall and completes the circuit

Question 26

What colour is the neutral wire

Answer 26

Blue

Question 27

What colour is the live wire

Answer 27

Brown

Question 28

What is the function of the Earth wire

Answer 28

Provides a path for current to flow from the case of the device to the ground if there is a fault

Question 29

What colour is the Earth wire

Answer 29

Striped

Question 30

What does the circuit breaker do and how do they work

Answer 30

Detect and stops excess current.
designed to ‘trip’ or shut itself off at predetermined amperage prevents the flow of current to that particular circuit

Question 31

Circuit breakers vs fuses

Answer 31

Circuit breakers respond quicker
more reliable
more sensitive
and unlike fuses they can be reset rather than replaced

Question 32

What voltages does each wire carry

Answer 32

Brown (live) - 230V
Blue (neutral) - 0V
Striped (earth) - 0V

Question 33

explain why heating occurs in wires as a result of electrical resistance ( discuss flow and collisions of electrons )

Answer 33

Electrons pushed through the wire will collide with the lattice.
When they do, energy is transferred from the electrons to the lattice, which causes the ions to vibrate more.
This is a heating effect: the wire gets hot.

Question 34

Why does the resistance across a filament lamp change as voltage increases

Answer 34

Filament lamp increases in temp due to more collisions of electrons when voltage is increased