Physics calculations question?

Question

(1) A kettle was rated at 3000 W and works from a 240 V mains electricity.Calculate the cost of using the kettle for 10 minutes if 1 kWh of electricity costs 14 cents.

(2) The cost of one unit of electricity is 14 cents. Calculate how much will it cost to use a hair dryer of 810 W of power rating for 15 minutes.

Answer 1

(1) P = 3000 W = 3 KW

t = 10 min = 1/6 h

Energy consumed = P x t = 3 x1/6 = 0.5 KWh

Cost = 0.5 x 14 = 7 cents

(2) P = 810 W = 0.81 KW

t = 15 min = 1/4 h = 0.25 h

Energy consumed = P x t = 0.81 x 0.25= 0.2025 KWh

Cost = 0.2025  x 14 = 2.84 cents

Answer 2

your data is missing a unit.  Electricity cost us a rate, that means money DIVIDED by a unit of time, minute or hour.  When you know the time factor.  simply Multiply the time of use by the Number of watts, to determine the watts per time and convert to kilowats and the correct time frame and and voila.