# CBSE – 7th Standard Science

## CBSE – 7th Standard Science

### Question Bank – Chapter 14 – Electric Current & Its Effects

CHAPTER 14

ELECTRIC CURRENT AND ITS EFFECTS

Q1. What does an electric circuit mean? What is the easy way to represent them?

Ans. A continuous and closed path of an electric current is called an electric circuit, an electric circuit can be represented by a circuit diagram.

Q.2 What is the heating Effect of electricity? What is its use in daily life?

Ans. When an electric current flows through a wire, the wire gets heated. It is the heating effect of current. This effect is used in heaters, elec. iron and room heaters.

Q.3 What is fuse? State its importance in a circuit?

Ans. Wires made from some special materials melt quickly and break when large electric currents are passed through them, electric fuses which prevent fires and damage to electric appliances.

Q.4  What materials are used to make fuse wire?

Ans. Very thin stee lwool and nichrome  are used to make a fuse. (The steel wool is commonly used for cleaning utensils and is available in grocery shops.). Wires made from some special materials melt quickly and break when large electric currents are passed through them. These wires are used for making electric fuses.

Q.5 Explain that fuses are safety device?

Ans.  In all buildings fuses are inserted in al electrical circuits. There is a maximum limit on the current which can safely flow through a circuit. If current exceeds safe limit, the wires may become overheated and may cause fire. If a proper fuse is there in the circuit, it will blow off and break the circuit. A fuse is thus a safety device to prevent damages to electrical circuits and possible fires

Q.6  What could be done to prevent loss by heating effect in bulbs?

Ans. Heating of bulb results in the wastage of electricity this wastage can be reduced by using fluorescent tube lights in place of the bulbs. Compact fluorescent lamps (CFLs) reduce wastage.

Q.7  What are the reason for short circuits?

Ans.  One reason for excessive currents in electrical circuits is the direct touching wires. This may happen if the insulation on the wires has come off and another reason for excessive current is connection of many devices to a single socket, these may cause overload and short circuit in the circuit.

Q.8  What happens when an electric current flows through a wire or near compass?

Ans. When an electric current flows through a wire, it behaves like a magnet and compass gets deflected .

Q.9  What is an electromagnet?

Ans. A current carrying coil of an insulated wire wrapped around a piece of iron is called an electromagnet.The electromagnets can be made very strong and can lift very heavy loads . The end of such a crane has a strong electromagnet attached to it.

The electromagnets are also used to separate magnetic material from the junk. Doctors use tiny electromagnets to take out small pieces of magnetic material that have accidentally fallen in the eye. Many toys also have electromagnets inside them.

Q.10 What are uses of electromagnets?
Ans. Strong electromagnets are used to make heavy cranes, electric bell and they are also used to separate magnetic material from the junk. Doctors use tiny electromagnets to take out small pieces of magnetic.

Q.11 What is a battery?

Ans. A combination of two or more cells is called a battery. Many devices such as torches, transistors, toys, TV remote controls, use batteries. However, in some of these devices the electric cells are not always placed one after the other Sometimes the cells are placed side by side.. There is usually a thick wire or a metal strip connecting the positive terminal of one cell to the negative terminal of the next cell. In order to help you to place the cells correctly in the battery compartment, ‘+’ and ‘–’ symbols are usually printed there.