PHYSICS · Multi-part · CBSE · Physics · Current Electricity · Current Electricity
Problem
A grain-drying electric heater is rated at 5.0 kW. It is switched on for 6 h every day for one complete week.
(i) Find the total electrical energy supplied to the heater during the week, expressing your answer first in kilowatt-hours.
(ii) Convert the result of part (i) into joules.
(iii) Laboratory measurements show that only 3.0×108J of the energy supplied is actually used to evaporate water from the grain. Calculate the percentage of the input energy that is effectively utilised for drying.
(iv) The mains voltage is 230V (assumed steady). Determine the total charge that flows through the heater in the week.