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Chapter 1: Nutrition in Plants

Chapter 2: Nutrition in Animals

Chapter 3: Fibre to Fabric

Chapter 4:Heat

Chapter 5: Acids, Bases and Salts

Chapter 6: Physical and Chemical Changes

Chapter 7: Weather, Climate and Adaptations of Animals to Climate

Chapter 8: Winds, Storms and Cyclones

Chapter 9:Soil

Chapter 10: Respiration in Organisms

Chapter 11:Transportation in Animals and Plants

Chapter 12:Reproduction in Plants

Chapter 13:Motion and Timers

Chapter 14: Electric Current and Its Effects

Chapter 15:Light

Chapter 16:Water: A Precious Resource

Chapter 17: Forests: Our Lifeline

Chapter 18: Wastewater Story

NCERT Solutions for class 7 science Chapter 13

Motion and Timers

NCERT Solutions for Class 7 Science chapter 14 Exercise Question

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

Answer
   

Question 2
Draw the circuit diagram to represent the circuit shown in Fig.14.21.

Answer

Question 3
Fig.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.

Answer

Question 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.

Answer

Question 5
Name any two effects of electric current.

Answer

i) Magnetic effect

ii)Heating effect

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

Answer

When ever current flow in wire it produce magnetic field around it So when we place compass near it needle get deflect due that field.

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

Answer

No , As circuit is not compelet so there in no flow of current it mean no magnetic field produce . If there is no magnetic field then compass needle do not show deflection

Question 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 .

Answer

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

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

(c) When current is switched ‘on’ in a room heater, it produces heat .

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

Question 9
Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) To make a battery 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 breaks. (T/F)

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

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

Answer

a) False

b) True

c) False

d) True

Question 10
Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.

Answer

No, because plastic bags are not magnetic materials.It can not be attracted by magnet so magnet cannot be used to separate plastic bags from a garbage heap.

Question 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.

Answer

No ,It is not a good idea to replace fuse by a piece of wire because fuse has very low melting point compare to wire.Whenever current get overload fuse melt and break the circuit to prevent short circuits.

Question 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.

Answer

the possible defects in the circuit may be bulb fused , may be wire should not connect properly, switch not work properly etc If Zubeda will check these then may be bulb will glow.

Question 13
In the circuit shown in Fig. 14.25

(i) Would any of the bulb glow when the switch is in the ‘OFF’ position?

(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?

Answer

i) No, the bulb will not glow

ii)All the bulbs glow simultaneously.