P2- Electricity

Question 1

Define current

Answer 1

the rate at which electrons flow past a point in a complete electrical circuit

Question 2

Whats meant by resistance in a circuit

Answer 2

Resistance is a measure of the opposition to the flow of current in an electrical circuit.

Unit: ohms

Question 3

What is meant by the potential difference of a circuit

Answer 3

Potential difference (or voltage) is a measure of energy, per unit of charge, transferred between two points in a circuit.

Question 4

What’s the equation for charge flow?

Answer 4

Q = It

Q- charge flow (coulombs, C)
I- current (A)
t- time (s)

Question 5

Cell diagram

Answer 5

Question 6

Battery circuit diagram

Answer 6

Question 7

Switch open and closed circuit symbol

Answer 7

Question 8

Bulb circuit symbol

Answer 8

Question 9

Fuse circuit symbol

Answer 9

Question 10

LED circuit symbol

Answer 10

Question 11

Resistor circuit symbol

Answer 11

Question 12

Variable resistor circuit symbol

Answer 12

Question 13

Ammeter circuit symbol

Answer 13

Question 14

Voltmeter circuit symbols

Answer 14

Question 15

Diode circuit symbol

Answer 15

Question 16

Ldr circuit symbol

Answer 16

Question 17

Thermistor circuit symbol

Answer 17

Question 18

What happens to the resistance of a thermistor ad it gets hotter?

Answer 18

Their resistance decreases as the temperature increases.

Question 19

Series circuits:
Potential difference is _______
Current is _________

Answer 19

Shared
The same everywhere

-resistance adds up
-cell potential difference adds up

Question 20

Parallel circuits:
Potential difference is_______
Current is________

Answer 20

the same across all components
shared between branches

Question 21

Graph for resistors in a series circuit

Answer 21

Question 22

Graph for the number of resistors in a series circuit

Answer 22

Question 23

Describe an experiment to investigate how adding resistors in series and parallel affects the total resistance of the circuit

Answer 23

Question 24

What colour is the neutral wire

Answer 24

Blue
The neutral wire completes the circuit

Question 25

What colour is the live wire ?

Answer 25

Brown The live wire provides the alternating potential difference between

Question 26

What colour is the earth wire?

Answer 26

Green and yellow It is for protecting the wiring and for safety- it stops the appliance casing from becoming live.

Question 27

What colour is the earth wire?

Answer 27

Green and yellow It is for protecting the wiring and for safety- it stops the appliance casing from becoming live.

Question 28

Why can the live wire give you an electric shock?

Answer 28

Since the live wire has a very large potential difference compared to the human body (0V) the live wire can cause shocks. When you touch a live wire, a large potential difference is produced across your body and a current flows through you

Question 29

The UK mains supply is an ac supply at around _____.

Answer 29

230V

Question 30

What’s the frequency of the ac mains supply?

Answer 30

50 Hz

Question 31

What are the functions of step-up and step-down transformers?

Answer 31

A “step-down transformer” is used to step voltage(p.d) down, while a “step-up transformer” is used to step voltage(p.d) up. Transformers all have two coils , primary, secondary joined with an iron core

Question 32

What is the national grid?

Answer 32

The National Grid is the system operator of Great Britain's electricity and gas supply. This includes England, Scotland and Wales. It is the company that manages the network and distribution of electricity and gas that powers all our homes and businesses.

Question 33

Explain why electricity is transferred by the national grid at a height p.d but low current

Answer 33

The transfer of electrical energy via the grid is very efficient. When currents in a cable are higher, more energy is dissipated to the surroundings through heating. As high currents waste more energy than low currents, electrical power is transported around the grid at a high voltage and a low current.

Question 34

What is the power rating of an appliance?

Answer 34

defines how much energy is being transferred from the mains to power the device

Question 35

Power=

Answer 35

Potential difference (V) x current (A)

Question 36

Energy transferred=

Answer 36

Power x time