English Medium कक्षा १० - CBSE Question Bank Solutions for Science

An electric bulb is connected to a 220 V generator. The current is 0.50 A. What is the power of the bulb?

Which of the following gases are filled in electric bulbs?

Assertion: Bending of wire decreases the resistance of the electric wire.

Reason: The resistance of a conductor depends on length, thickness, nature of material and temperature of the conductor.

An electric kettle consumes 1 kW of electric power when operated at 220 V. A fuse wire of what rating must be used for it?

B₁, B₂ and B₃ are three identical bulbs connected as shown in Figure. When all the three bulbs glow, a current of 3A is recorded by the ammeter A.

1.  What happens to the glow of the other two bulbs when the bulb B₁ gets fused?
2. What happens to the reading of A₁, A₂, A₃ and A when the bulb B₂ gets fused?
3. How much power is dissipated in the circuit when all the three bulbs glow together?

Three incandescent bulbs of 100 W each are connected in series in an electric circuit. In another circuit another set of three bulbs of the same wattage are connected in parallel to the same source.

1. Will the bulb in the two circuits glow with the same brightness? Justify your answer.
2. Now let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.

It would cost a man Rs. 3.50 to buy 1.0 kW h of electrical energy from the Main Electricity Board. His generator has a maximum power of 2.0 kW. The generator produces energy at this maximum power for 3 hours. Calculate how much it would cost to buy the same amount of energy from the Main Electricity Board.

A student boils water in an electric kettle for 20 minutes. Using the same mains supply he wants to reduce the boiling time of water. To do so should he increase or decrease the length of the heating element? Justify your answer.

Two students decided to investigate the effect of water and air on iron object under identical experimental conditions. They measured the mass of each object before placing it partially immersed in 10 ml of water. After a few days, the object were removed, dried and their masses were measured. The table shows their results.

What might be the reason for the varied observations of the two students?

In which of the following applications of Iron, rusting will occur most? Support your answer with valid reason.

A	B	C	D

In a set up the students coated iron nails with zinc metal and noted that, iron nails coated with zinc prevents rusting. They also observed that zinc initially acts as a physical barrier, but an extra advantage of using zinc is that it continues to prevent rusting even if the layer of zinc is damaged. Name this process of rust prevention and give any two other methods to prevent rusting.

An electric kettle consumes 1 kW of electric power when operated at 220 V. A fuse wire of what rating must be used for it?

An electric kettle of 2 kW is used for 2h. Calculate the energy consumed in 

1. kilowatt hour and
2. joules.

What is the heating effect of electric current?

Write an expression for the amount of heat produced in a resistor when an electric current is passed through it stating the meanings of the symbols used.

State the law that explains the heating effect of current with respect to the measurable properties in an electrical circuit.

Anannya responded to the question: Why do electrical appliances with metallic bodies are connected to the mains through a three-pin plug, whereas an electric bulb can be connected with a two-pin plug?

She wrote: Three-pin connections reduce heating of connecting wires.

1. Is her answer correct or incorrect? Justify.
2. What is the function of a fuse in a domestic circuit?