Electric Current and its Effects

Q1. Fill in the blanks.

                          i.        Longer line in the symbol for a cell represents its positive terminal.

                         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.

Q2. 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

Q3. What is electric current?

Ans. Electric current is flow of electrons.

Q4. Why does light bulb get hot?

Ans. Light bulb gets hot due to heating effect of the electric current.

Q5. Who discovered magnetic effect of current?

Ans. Hans Christian Oersted discovered magnetic effect of current.

Q6. How does a bulb glow?

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

Q7. Write some uses of battery.

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

Q8. Which wire used in electric heater and why?

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

Q9. What is filament?

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

Q10. Is it possible for a wire to melt and break? Why?

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

Q11. What is the heating effect of the electric current?

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

Q12. Who invented electric bulb?

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

Q13. What are the uses of heating effect of electric current?

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

Q14. Explain the symbol of electric cell.

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

Q15. Name any two effects of electric current.

Ans. The two effects of electric current are:

                           i.        Heating effect of electric current

                         ii.        Magnetic effect of the electric current

Q16. Why are fuse wires not used in circuit containing electric cell?

Ans. 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.

Q17. What is an electric circuit?

Ans. 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.