question_answer

       (a) Define SI unit of energy. How it is related to kilowatt-hour? (b) Find the cost of using three bulbs each of 60 W in 30 days if each bulb is used 5 h daily, rate per unit is given as Rs. 3.    

Answer:

   (a) 1 J is the amount of work done on an object when a force of IN displaces it by 1m along the line of action of the force.                     1 J = 1 Ws  (b) Energy consumed by 3 bulbs in one day Energy consumed by bulbs in 30 days = 0.9 x 30 =27 kWh           Cost of 1 kWh= ` 3 Cost of 27 kWh = 3 x 27 = ` 81