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There are six 40 W and two 100 W lamps ,...

There are six 40 W and two 100 W lamps , four 40 W fans and a 1000 W electric heater in a house .If in April , each lamp runs for 5 hours a day , each fan 15 hours a day and the heater 2 hours a day , what will be the electric bill for that month ? It may be supposed that the main supply voltage is 200 V and cost of each BOT unit = Rs. 1.50.
Which one of the give three wires of rating 5 A , 10 A and 15 A will be appeopeiate for connection in the main switch ?

Text Solution

Verified by Experts

Number of days in April = 30
Electricl energy consumed by the lamps
=`((6xx40+2xx100)xx5xx30)/(1000)=66"BOT unit"`
Electrical energy consumed by the fans
= `((4xx40)xx15xx30)/(1000)=72"BOT unit"`
Electrical energy consumed by the heater
`(1000xx2xx30)/(1000)=60"BOT unit"`
`therefore` Monthly expenditure of electricity
`=(66+72+60)xx1.5 ` = R.s 297
Again , total power of the appliances
`=(6xx40)+(2xx100)+(4xx40)+1000=1600W` If all the aplliances run simultaneously , according to the relation , `P=VxxI`
we have , `I=(P)/(V)=(1600)/(200)=8A`
So , 10 A fuse will be appropriate in the main switch because 5 A fuse will melt nad there is no need of 15 A fuse .
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