Bulb is rated at 200 V, 100 W. Calculate its resistance. Five such bulbs are lighted for 4 hours daily. Calculate the units of electrical energy consumed per day. What would be the cost of using these bulbs per day at the rate of Rs. 4.00 per unit?

Question

Philoid · Accepted Answer

We know that for an electric appliance

Resistance will be given as

Now, here

P = 100 W

V = 200 volts

So, R =

R =

Thus, resistance of the bulb is R = 400 Ω

Now, electric energy consumed will be

E = power of each unit × time.

⇒ E = p × t.

Here

P = 100 W

t = 4 hours

So,

E = 100 x 4 = 400 Watt per hour

Dividing by 1000 to convert into Kilo Watt per hour

E = kWh

Electrical energy consumed is kWh

The total cost of electricity = total unit of energy consumed x cost per unit =

Cost = 0.4kWh x 4 Rs/kWh = Rs1.6

Thus, total cost (daily) = Rs. 1.6