17th of March 2017

In a class there are four ceiling fans of power 60W and six tube lights of power 40W. These are operated from 9 AM to 3 PM daily.

(i) Calculate the units of energy consumed in one day by one class.

(ii) If two block periods of 30 minutes duration are there for class for games and the fans and lights are switched off, how much money can be saved by one class in one day.(cost of one unit is Rs.4.00)

Please answer quickly 2morrow is my exam....

Shyam Soman.s - CBSE - Class IX

Thursday, March 16, 2017 at 17:32:PM


Hi Shyam,

Providing an entire solution on the Live chat platform is not feasible. You can post this query on the ask the expert section for a detailed solution.

However, the following steps will help in solving the question:

Part (a)

1) Calculate total power for all the four fans and six lights. Convert that into kilowatts.

2) calculate total time of operation in hours.

3) Total energy consumed is Power into time. You will get this in kilowatt hours. So, that many units have been consumed.

Part (b)

1) Two block periods means one hour. So, electricity is saved for one hour.

2) Calculate units saved for this one hour.

3) Multiply the units by cost per unit and you will get the total cost saved.

Friday, March 17, 2017 at 18:14:PM