domestic electricity

Question 1

kwh equation

Answer 1

units of energy= power (kw) x time (hours)
cost= units of energy x cost per unit

Question 2

direct current

Answer 2

comes from batteries and cells
only flows in one direction at a steady size
dc is not efficient over long distances

Question 3

Alternating current

Answer 3

comes from the ring mains
it’s constantly changing direction and size
it’s efficient over large distances

Question 4

what is a fuse

Answer 4

a fuse is a safety device in an electric plug or circuit
it consists of a piece of wire that melts when there is a fault so electricity stops

Question 5

what colour is each wire in the plug

Answer 5

live wire = brown
neutral= blue
earth= green/yellow

Question 6

live wire

Answer 6

carries the current from the mains supply to the switch or appliance at a high voltage (230)

Question 7

neutral wire

Answer 7

blue
completes circuit by carrying away the current

Question 8

earth wire

Answer 8

stops the appliance from becoming dangerous
send the unwanted electricity to the ground

Question 9

miniature circuit breaker

Answer 9

mcb can be reset and uses an electromagnet to open a switch if the current gets too high
they are faster than fuses

Question 10

residual current circuit breakers

Answer 10

rccb switches off the current when there is a difference between the current in the lives and neutral wires
rccbs are more sensitive than mcbs

Question 11

advantages of ring mains

Answer 11

there are two paths for cutrent so if one thing breaks or stops working the rest still work
sockets can be placed anywhere on the ring

Question 12

what is the ring mains

Answer 12

the ring mains forms a circuit where the live neutral and earth wire form a loop of cable going from the consumer unit to all of the sockets and then back to the consumer unit

Question 13

wave amplitude

Answer 13

the maximum displacement

Question 14

crest and trough

Answer 14

crest- highest part of the wave
trough- lowest part of the wave

Question 15

wave frequency

Answer 15

number of waves every second (Hertz)

Question 16

wave speeds

Answer 16

how many waves per second
speed = distance divided by time

Question 17

what is the wave equation

Answer 17

wave speed (v) equals frequency (Hz) multiplied by wavelength (m)

Question 18

what is the relationship between frequency and wavelength

Answer 18

as frequency increases wavelength decreases
frequency doubles wavelength halves

Question 19

what is a transverse wave

Answer 19

oscillations are perpendicular to the direction of energy transfer
)electromagnetic waves) )water waves)

Question 20

longitudinal waves

Answer 20

oscillations that are parallel to direction of energy transfer (some regions are more spread out )

( sound waves shock waves )