Class 7 Science NCERT Chap 14 Solution

 Chapter 14

ELECTRIC CURRENT AND ITS EFFECTS

Here is answer of chapter 14 ELECTRIC CURRENT AND ITS EFFECTS NCERT science of class 7 which helps students to better understand topics of chapter 14 ELECTRIC CURRENT AND ITS EFFECTS.

Exercise Questions-

Ques 1.Draw in your notebook the symbols to represent the following components of electrical  circuits: connecting wires switch wires, switch in the OFF position, bulb, cell, switch in the ON position and battery.

Ans.

Ques 2. Draw the circuit diagram to represent the circuit shown in figure.

Ans.

Ques 3. Figure 14.22 shows four cells fixed on a board. Draw  lines to indicate how you will connect their terminals with wires to make a battery of four cells.

Ans. To construct a battery, the negative terminal of one cell should be connected to the positive terminal of the other cell. Therefore the cells should be connected as shown in figure.

Ques 4. The bulb in the circuit shown in Fig 14.23 does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.

Ans. Terminals of the battery should be connected properly. Positive terminal of one battery should be connected to the negative terminal of another battery.

Ques 5. Name any two effect of electric current.

Ans. A current carrying conductor can show a heat effect and a electron magnetic effect  which can be considered as the two effects of electric current.

Ques 6. When the current is switched on through a wire, a compass needle kept nearby gets deflected from the north south position. Explain.

Ans.  A current carrying wire creates a magnetic field around it. The needle of  a compass is a tiny  magnet which points in a north south direction with a compass  needle nearby and current is allowed to pass through it, the magnetic  field of the compass  needle, hence it shows a deflection.

Ques 7. Will the compass needle show deflection   when the switch in the circuit shown by Fig 14.24 is closed?

Ans. From the given circuit we observe that there is neither a cell nor a battery. Hence, there  is no source of electricity. Through the switch in the circuit is closed,there is no passage of current. Hence, it does not show any effect on the magnetic needle kept close by the circuit. 

Ques 8. Fill in the blanks:-

a)Longer line in the symbol for a cell represents its _______ terminal.

b) The combination of two or more cells is called a _______.

c) When current is switched 'on' in a room heater,it__________.

d)The safety device based  on the heating effect of electric current is called a _______.

Ans. a) positive

b)battery

c)produces heat

d) fuse 

Ques 9. Mark 'T' if the statement is True and 'F' if is False:-

a)To make a bsttery of two cells,the negative terminal of one cell is connected to the negative terminal of the other cell.(T/F)

b)When the electric current through the fuse exceeds a certain limit,the fuse wire melts and break.

c)An electromagnet does not attract a piece of iron(T/F)

d)An electric bell has an electromagnet.(T/F)

Ans. a)false

b)True

c)false

d)True

Ques 10. Do you think an electro magnet can be 

used for seperating plastic bags from a garbage heap? Explain.

Ans. No, an electro magnet cannot be used for seperating plastic bags from garbage heap. Electromagnets are used to seperate magnetic materials from the junk. As, plastic is a non magnetic  materials it cannot be seperated  from the junk using electromagnets.

Ques 11. An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire.Would you agree? Give reasons for your response.

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

Therefore, I would not agree to replace a fuse by  a piece of wire has particular properties. Any wire has particular properties. Any wire cannot  act as fuse wire. We should always use proper uses which have been specified for particular applications, carrying the ISI mark which indicates that the advice is manufactured according  to standard.

Ques 12.Zubeda made an electric circuit using a cell  holder shown in Fig.14.4 a switch and a bulb. When she put the switch in the  'ON'position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.

Ans. Possible defects can be as follows:-

a)The two cells may not be connected properly.

b)The rubber band used in the cell holder is unable to hold the cells in contacts with each other and the circuit is incomplete  and current is not following in the circuit.

The following conditions are to be satisfied for the  bulb to glow:-

a)The positive terminal  of the cell should be connected to the negative terminal of another cells.

b) Check the wire connections properly.

c) Check the condition of the bulb whether it is working or fused.

Ques 13. In the circuit shown in Fig.14.25.

I)Would any of the bulb glow  when the switch is in the Off  position?

Ans. No bulb will glow when the switch is in the Off position are there is no current in the circuit 

Unless and untill the switch is in the ON position  no bulb will glow.

ii) What will be the order in which the  bulbs A, B and C will glow. When the switch is moved to the ON position?

Ans. When the switch is in the ON all the bulbs will glow at the same time as they are connected to the same battery and switch.

This is the complete solution and explaination of Chapter 14 ELECTRIC CURRENT AND ITS EFFECT of Class 7 Science NCERT.

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