Electricity

Question 1

what is electric current?

Answer 1

the rate of flow of charge
or
how much charge flows per second

Question 2

what are the symbol and units for electric current?

Answer 2

I

measured in amps (A)

Question 3

what is the formula for current?

Answer 3

current = charge (c) / time (s)

charge measured in coulombs and time in seconds

Question 4

why is charge the same value anywhere around a circuit?

Answer 4

charge is not used up by the components in a circuit (because energy can only be converted) so the amount of charge is the same anywhere

Question 5

what is voltage and what is it measured in?

Answer 5

the amount of energy converted per coulomb of charge flowing

measured in joules

so 1 volt is really 1 joule per coulomb

Question 6

what is the formula for voltage?

Answer 6

voltage = energy converted / charge flowing

Question 7

what is resistance?

Answer 7

a measure of how difficult it is for electric current to flow
a property of an electrical component

Question 8

what is the formula for resistance?

Answer 8

voltage (v) = current (A) x resistance (Ω)

Question 9

what is Ohm’s law?

Answer 9

“voltage across a component is directly proportional to the current provided the temperature of the component doesn’t change”

Question 10

what is the voltage equation?

Answer 10

voltage = energy converted / charge flowing

Question 11

what is power?

Answer 11

the amount of energy converted per second

measured in Watts

Question 12

if a bulb is 36 Watts, what does this mean?

Answer 12

the bulb converts 36J of energy per second

Question 13

what is the power equation?

Answer 13

power = energy / time 
P = E/t

Question 14

what is the electrical power equation?

Answer 14

electrical power = voltage x current?

P = VI

Question 15

what is the purpose of a fuse?

Answer 15

to stop a current flowing when a fault occurs

Question 16

how does a fuse work?

Answer 16

the large current will cause the fuse wire in the fuse to melt
the circuit will be broken

Question 17

what does the earth wire do?

Answer 17

the earth wire is connected to the casing of a device (but only if the casing is metallic)

if a fault develops and the case becomes live, a huge current will flow down the earth wire into the ground

the current will flow through the fuse and melt it, thus breaking the circuit

Question 18

what devices need earth wires and what is the name and symbol of a device that doesn’t require earthing?

Answer 18

devices with metal casing need an earth wire ie a kettle

devices that don’t require an earth wire are called “double insulated” and are stamped with this symbol
[■]

Question 19

how can you identify the live wire in a plug?

Answer 19

the live wire is brown and will be attached to the fuse. it carries the current to the appliance

Question 20

how can you identify the neutral wire in a plug?

Answer 20

the neutral wire is blue and will not be attached to the fuse.
it carries the current away from the appliance and completes the circuit

Question 21

how can you identify the earth wire?

Answer 21

the earth wire is green and yellow

Question 22

what is the name of the plastic bridge that holds the wire in place in a plug

Answer 22

the cable grip