Power Flashcards
1
Q
what is the definition of power?
A
power is the rate at which energy is transferred or the rate at which work is done
2
Q
what are the two potential formulas for power?
A
energy transferred (J) / time (s)
or
work done (J) / time (s)
3
Q
when a car stops, 40,000J of work is done by the brake in a time of 5 seconds. calculate the power of the brakes
A
E/T = 40,000/5 = 8,000W
4
Q
what is the formula for cost of electricity?
A
cost (£) = kWh x price (per kWh)
(kW x hours)
5
Q
a games console has a power of 2kW and is used for 1.5 hours. work out the cost of electricity
(tariff = 5p)
A
kWh = 2 x 1.5 = 3kWh
price = tariff = 5p
= 3kWh x 5p = 15p / £0.15
