Correct Answer - Option 1 : 300

**Concept:**

Power (P): The rate of doing work is called power and it is also known as the rate of consumption of energy.

- The SI unit of power is "watt".
- 1 Watt = 1 Joule/second.

- The commercial unit of electric energy is kilowatt or the Board of Trade (B.O.T) unit.

One kilowatt-hour: It is defined as the electric energy consumed by the appliance of 1 kilowatt in one hour.

1 kilowatt-hour = 1 kilowatt × 1 hours = 1000 watt × 3600 s

**1 kWh = 3600000 joules = 3.6 × 106 J**

__Calculation:__

__Given:__

P = 100 W, t = 10hr, D = 30 days, Cost per unit (c) = Rs 10

Energy consumed (E) in 30 days = P × t × D

= 100 × 10 × 30

E = 30000 Wh

**E = 30 kWh**

**Bill for electricity = E × c = 30 × 10 = Rs 300**