Domestic Electricity Answers
1) Voltage 1V, period of 6s so a frequency of 0.15Hz
Voltage 2V, period of 6s so a frequency of 0.15Hz
Voltage 2V, perod of 6s so a frequency of 0.15Hz
Voltage 2V, period 3.5s so a frequency of 0.3Hz
3a) If too much current flowed through the device, it could heat up and cause a fire.
b) If charge built up on the device, without an Earth wire, it could cause a spark and electrocute someone.
4) 13A because all the others are too low: they will blow as soon as the device is turned on.
5) Power = voltage x current, so current = power/voltage=2400/240 = 10A
6a) Power =voltage x current = 3 x 10= 30W
b) Energy = power x time (seconds) =30 x 4 x 60 x 60= 432 000J or 432kJ
c) Energy (kWh) = power (kW) x time (hours) = 0.03 x 4 =0.12kWh
d) Cost = 9p x 0.12 = 1.08p
7) Having a high voltage means that the same amount of power can be transported at a low current. If the current was too high, energy would be lost due to an increased resistance from the wire heating up.
Voltage 2V, period of 6s so a frequency of 0.15Hz
Voltage 2V, perod of 6s so a frequency of 0.15Hz
Voltage 2V, period 3.5s so a frequency of 0.3Hz
3a) If too much current flowed through the device, it could heat up and cause a fire.
b) If charge built up on the device, without an Earth wire, it could cause a spark and electrocute someone.
4) 13A because all the others are too low: they will blow as soon as the device is turned on.
5) Power = voltage x current, so current = power/voltage=2400/240 = 10A
6a) Power =voltage x current = 3 x 10= 30W
b) Energy = power x time (seconds) =30 x 4 x 60 x 60= 432 000J or 432kJ
c) Energy (kWh) = power (kW) x time (hours) = 0.03 x 4 =0.12kWh
d) Cost = 9p x 0.12 = 1.08p
7) Having a high voltage means that the same amount of power can be transported at a low current. If the current was too high, energy would be lost due to an increased resistance from the wire heating up.