Electric Current and Its effects Class 7 Worksheet Science Chapter 10

Q.1. True/False
(i) To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell.

False

(ii) When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks.

True

(iii) An electromagnet does not attract a piece of iron.

False

(iv) An electric bell has an electromagnet.

True

Q.2. Fill in the blanks.
(i) Longer line in the symbol for a cell represents its ____ terminal.

positive

(ii) The combination of two or more cells is called a ____.

battery

(iii) When current is switched ‘on’ in a room heater, it ____.

produces heat

(iv) The safety device based on the heating effect of electric current is called a ____.

fuse

Q.3. What is electric current?

Electric current is flow of electrons.

Q.4. Who discovered magnetic effect of current?

Hans Christian Oersted discovered magnetic effect of current.

Q.5. Which wire used in electric heater and why?

Nichrome wire is used in electric heater because it has a high melting temperature.

Q.6.  Is it possible for a wire to melt and break? Why?

Yes, if a large current passes through a wire, the wire may become so hot that it may even melt and break.

Q.7. Who invented electric bulb?

The credit for the invention of the electric bulb is usually given to Thomas Alva Edison, though others before him had worked on it.

Q.8. Write some uses of battery.

Many devices such as torches, transistors, toys, TV remote controls, use batteries.

Q.9. What is filament?

In the bulb there is a thin wire, called the filament, which glows when an electric current passes through it.

Q.10. What is the heating effect of the electric current?

The wire gets hot when an electric current passes through it. This is the heating effect of the electric current.

Q.11. What are the uses of heating effect of electric current?

Electrical appliances, such as immersion heaters, hotplates, irons, geysers, electric kettles, hair dryers uses of heating effect of electric current.

Q.12. Name any two effects of electric current.

The two effects of electric current are:
(i) Heating effect of electric current
(ii) Magnetic effect of the electric current

Q.13. What is an electric circuit?

The electric circuit provides a closed path for electricity to pass between the two terminals of the electric cell. The bulb glows only when current flows through the circuit.

Q.14. Explain the symbol of electric cell.

In the symbol of the electric cell, the longer line represents the positive terminal and the thicker, shorter line represents the negative terminal.

Q.15. Why are fuse wires not used in circuit containing electric cell?

Fuse wires are not used in circuit containing electric cell because the amount of current follow is low and if the circuit breaks there is no risk of fire.

Q.16. Why a fused bulb does not glow?

A break in the filament of an electric bulb means a break in the path of the current between the terminals of the electric cell. Therefore, a fused bulb will not glow as current does not passes through its filament.

Q.17. Why should we look for ISI mark on electrical appliances?

Before buying any electrical appliance we should look for ISI mark because this mark ensures that the appliance is safe and wastage of energy is the minimum.

Q.18. We could not see element in electrical appliances. Give reason.

We could not see element in electrical appliances because electrical appliances, such as immersion heaters, hotplates, irons, geysers, electric kettles, hair dryers, have elements inside them.

Q.19. Sometimes the cells are placed side by side. Then how are the terminals of the cells connected?

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.

Q.20. On what factors does the heat produced in a wire depend?

The amount of heat produced in a wire depends on its material, length and thickness. Thus, for different requirements, the wires of different materials and different lengths and thicknesses are used.