Electricity

Question 1

What is charge flow and how do you calculate it + unites

Answer 1

the rate of flow of electrical charge
charge flow = current x time
coulombs

Question 2

what is resistance and what happens if it is high

Answer 2

Resistance is the measure of how it resists the flow of charge
The higher the resistance:
the more difficult it is for the charge to flow
the lower the current

Question 3

what is potential difference and how is it calculated + units

Answer 3

potential difference tells us the difference in electrical potential from one point in a circuit to another (an electrical push) - (the opposite of resistance)
potential difference = current x resistance
volts

Question 4

what does a straight line, steep gradient, and shallow gradient represent through a potential difference graph

Answer 4

A straight line = the voltage and current are directly proportional
A steep gradient = low resitance
A shallow gradient = high resistance

Question 5

How are resistors, filament lamps and diodes represented on graphs

Answer 5

resistors = straight line graph (linear)
Filament Lamp= curved graph
Diodes = horizontal line along the x-axis

Question 6

Four features of a parallel circuit (current , PD, total resistance)

Answer 6

• The PD across all components is the same (v)
• The total current drawn from the power supply is the sum of the current through separate components
• The total resistance of two resistors is less than the resistance of the smallest individual resistors
• Adding resistors in parallel reduces total resistance

Question 7

Four features in a series circuit (current, PD, total resistance)

Answer 7

• There is the same current through each component
• The total PD across of the power supply is shared through components
• The total resistance of the components is the sum of resistance through each component
• Adding resistors in parallel increases the total resistance

Question 8

How is power in circuits calculated

Answer 8

power = potential difference x current
power = (current)’2 x resistance
watts

Question 9

features of a direct current and where is it used

Answer 9

• has a potential difference that is always positive or negative
• is the type of current used by cells and batteries

Question 10

features of an alternating current and use

Answer 10

• has a potential difference that alternated form positive to negative
• is the type of current used in main electricity

Question 11

What is the current and function of each wire in a plug

Answer 11

Earth 
- green/yellow 
-safety wire to stop the appliance becoming live
Neutral
-blue
-completes the circuit and carries current away from appliance
Live 
-brown
-carries current to the appliance

Question 12

Why can someone still get electrocuted when touching a live wire even when off

Answer 12

they will make a pathway for the current to flow by creating a potential difference from the live wire to the earth.

Question 13

What is power and how can it be calculated

Answer 13

Power is the rate at which energy is transferred and work is done
power = energy transferred / time
power = work done / time

Question 14

What is efficiency and how is it calculated

Answer 14

Efficiency is the rate of useful energy out to total energy in
efficiency = useful energy / total energy transfer

Question 15

what is work done and how is it calculated

Answer 15

work is done when charge flows
energy transferred = power x time
energy transferred = charge flow x potential difference

Question 16

How is the national grid efficient

Answer 16

-Power station
using a small number of large power stations as most use steam turbines which are more efficient at higher temperatures
-Step-up transformers
reduces the heating effect caused by current flowing through transmission cables

Question 17

What happens during friction

Answer 17

• friction moves negatively charged electrons from one material to another
• the object that gains electrons becomes negatively charged
• the object that looses electrons becomes positively charged

Question 18

Why is friction not seen with conductors

Answer 18

as they conduct the charge to earth so it cannot build up

Question 19

Why is an electrical spark caused

Answer 19

as the charge on an isolated object increases the potential difference between the objects and earth increases
- when the potential difference becomes high enough, the spark may jump across the gap form any conductor near it