A bulb is rated at 200V -40W. What is its resistantt ? 5 such bulbs are lighted for 5 hours. Calculate the electrical energy consumed ? Find the cost if the rate is 5.10 per KWh.

Explanation

V = 200 V,P = 40 W
P =VI
`I=(P)/(V) =(40)/(200) = (1)/(5)` A
`R= (V)/(I) = (20)/((1)/(5))`
`=200xx5=1000 Omega`
Total power `=40Wxx5=200W`
Time =5 hrs
Electrical energy `= 200 Wxx5 hrs`
=1000 Wh
= 1 KWh.
Cost of 1 Kwh = 5.10 Rs.