English Medium कक्षा १० - CBSE Question Bank Solutions for Science

Which quantity has the unit of watt?

What is the meaning of the symbol kWh? Which quantity does it represent?

An electric lamp is labelled 12 V, 36 W. This indicates that it should be used with a 1 V supply. What other information does the label provide?

Define watt. Write down an equation linking watts, volts and amperes.

Define watt-hour. How many joules are equal to 1 watt-hour?

An electric bulb is connected to a 220 V power supply line. If the bulb draws a current of 0.5 A, calculate the power of the bulb.

In a house two 60 W electric bulbs are lighted for 4 hours, and three 100 W bulbs for 5 hours everyday. Calculate the electric consumed in 30 days.

A bulb is rated as 250 V; 0.4 A. Find its : (i) power, and (ii) resistance.

An electric motor takes 5 amperes current form a 220 volt supply line. Calculate the power of the motor and electric energy consumed by it in 2 hours.

Which uses more energy: a 250 W TV set in 1 hour or a 1200 W toaster in 10 minutes?

An electric kettle connected to the 230 V mains supply draws a current of 10 A. Calculate:

(a) the power of the kettle.
(b) the energy transferred in 1 minute.

A 2 kWh heater, a 200 W TV and three 100 W lamps are all switched on from 6 p.m. to 10 p.m. What is the total cost at Rs 5.50 per kWh?

What is the maximum power in kilowatts of the appliance that can be connected safely to a 13 A ; 230 V mains socket?

An electric fan runs from the 230 V mains. The current flowing through it is 0.4 A. At what rate is electrical energy transferred by the fan?

What is meant by "electric power"?

Write the formula for electric power in terms of potential difference and current.

The diagram below shows a circuit containing a lamp L, a voltmeter and an ammeter,. The voltmeter reading 3 V and the ammeter reading is 0.5 A. 

 What is the resistance of the lamp?
 What is the power of the lamp?

Define kilowatt-hour. 

 How many joules are there in one kilowatt-hour?

Calculate the cost of operating a heater of 500 W for 20 hours at the rate of Rs 3.90 per unit.