T2- electricity

Question 1

what is electric current

Answer 1

the flow of charge

Question 2

equatin for charge

Answer 2

Q=IT

Question 3

what 2 factors does the current in a circuit depend on

Answer 3

PD
resistance

Question 4

equations for PD

Answer 4

V=IR
V=E/Q

Question 5

what is an ohmic conductor
what condition is required for it

Answer 5

conductor for which current and PD are directly proportional
temperature must be constant

Question 6

4 components for which resistance is not constant as current changes

Answer 6

lamps
diodes
thermistors
LDRs

Question 7

describe PD in series

Answer 7

shared across all components

Question 8

describe PD in parallel

Answer 8

same across all components

Question 9

if 2 resistors are connected in parallel, what is said about their total resistance

Answer 9

their total resistance is less than the smallest of the 2 individual resistances

Question 10

if 2 resistors are connected in series, what is said about their total resistance

Answer 10

their total resistance is equal to the sum of the 2 individual resistances

Question 11

describe current in series

Answer 11

current is the same everywhere- charge only has one path to flow through

Question 12

describe current in parallel

Answer 12

current is shared between loops- when the charge reaches a junction, it splits

Question 13

how should you connect an ammeter in a circuit to measure current

Answer 13

connect in series with the component they’re measuring current through

Question 14

how should you connect a voltmeter in a circuit to measure PD

Answer 14

connect in parallel with the component they’re measuring the PD of

Question 15

advantage of using lamps in parallel

Answer 15

if one blows, the rest will still receive current (if the circuit is complete)

Question 16

what is alternating current

Answer 16

current that continuously changes direction

Question 17

what is direct current

Answer 17

current flows in one direction

Question 18

what is the frequency and voltage of UK mains electricity supply

Answer 18

frequency- 50Hz
voltage- 230V

Question 19

what colour is earth wire

Answer 19

green and yellow stripe

Question 20

what colour is neutral wire

Answer 20

blue

Question 21

what colour is live wire

Answer 21

brown

Question 22

why does earth wire does and doesn’t carry current

Answer 22

normally doesn’t carry current
if appliance becomes live, current will flow into the ground

Question 23

what potential is neutral wire at

Answer 23

0V

Question 24

what is the PD between earth and live wires

Answer 24

230V

Question 25

what is the purpose of neutral wire

Answer 25

completes circuit by connecting appliance back to mains supply

Question 26

where is earth wire connected to on metal appliances?

Answer 26

connected to the metal casing of the appliance
if live wire becomes loose and touches the casing, current will flow through earth wire, preventing electrocution

Question 27

equations for power in a circuit

Answer 27

P=IV
P=I²R

Question 28

what do step-up transformers do

Answer 28

increase PD
connect power stations to transmission cables

Question 29

what do step-down transformers do

Answer 29

decrease PD
connect transmission cables to domestic buildings

Question 30

why do transmission cables transfer electricity at high potentials

Answer 30

high potential=low current
low current= less energy wasted as heat
so it’s more efficient

Question 31

why does potential need to be decreased

Answer 31

lower potentials are safer for domestic use and reduces chance of electrocution
appliances are designed for 230V