Selina solutions concise physics class 7 icse Solutions for Chapter 7 electricity and magnetism

Q1) True or false

1. A current-carrying coil, when suspended freely, can rest in any direction :

2. A coil carrying current behaves like a magnet :

3. In an electromagnet, the core is made up of copper :

4. An electric bell uses an electromagnet :

5. An electromagnet with the soft iron core is a temporary magnet :

6. We use cells as the source of electricity to run an electric immersion rod. :

7. A torch bulb glows if the terminals of the bulb are connected to the terminals of a cell by the metallic wire. :

8. Wool is a conductor of electricity :

9. Silver is an insulator of electricity :

10. Our body is a conductor of electricity :

11. For a circuit to be complete, every part of it must be made up of conductors :

12. All metals are conductors of electricity :

13. The switch should not to be touched with wet hands :

14. A switch is an on-off device in an electric circuit. :

Q2) Fill in the blanks

1. A magnet has ___ poles.
2. Like poles ______ each other and unlike poles _____
3. An electromagnet is used to separate large masses of ____ scrap.
4. The strength of the magnetic field of an electromagnet is increased by inserting a core of soft ___.
5. In a torch we use a _____ as the source of electricity.
6. To light a table lamp and to run a refrigerator, we use ____ as the source of electricity.
7. A group of two or more cells is called a _____.
8. _ pass electricity through them.
9. __ do not pass electricity through them.

Q3) Match the following.

Q4)

a) A freely suspended magnet rests in

1. East-west direction
2. North-south direction
3. North-east direction
4. North-west direction

b) Electromagnets are made up of

1. Steel

2. Copper

3. Brass

4. Soft iron

c) An electromagnet is used in

1. Electric oven

2. Ammeter

3. Electric bell

4. Radio set

d) The purpose of armature in an electric bell is

1. To make and break the circuit

2. To produce sound

3. To produce magnetic field

4. To provide spring action

e) In a torch, the source of electricity is

1. The bulb

2. The switch

3. The cell

4. The mains

f) Electricity can flow through

1. Wood

2. Rubber

3. Plastic

4. Copper wire

g) Electricity does not flow through

1. Human body

2. Animal body

3. Rubber

4. Silver

h) We should not touch the switch with wet hands otherwise

1. Electricity may pass through our body

2. Electricity may not pass through the appliance

3. Circuit may break

4. The switch may get off

Q1) State two properties of a bar magnet.

Q2) How to test whether a given rod is a magnet or not?

Q3) How will you test whether a given rod is made of iron or not?

Q4) YOu are given two similar bars. One is a magnet and the other is of soft iron. How will you distinguish and identify them?

Q5) You are given a magnet. How will you use it to find north-south direction at a place?

Q6) Describe a simple experiment to illustrate that like poles of two magnets repel each other while the, unlike poles, attract.

Q7) ‘Poles exist in pair” Comment on this statement.

Q8) What is a magnetic compass? State its use

Q9) Explain the meaning of the term magnetic field.

Q10) What is an electromagnet?

Q11) NAme the material of an electromagnet.

Q12) Draw a labelled diagram to make a soft iron bar as an electromagnet. Describe in steps the procedure.

Q13) You are given a U shaped soft iron piece, insulated copper wire and a battery. Draw a circuit diagram to make a horseshoe electromagnet.

Q14) Name two factors on which the strength of magnetic of an electromagnet depends.

Q15) Name two factors on which the strength of the magnetic field of an electromagnet depends.

Q16) State two common uses of electromagnets.

Q17) NAme a domestic device in which an electromagnet is used.

Q18) Draw a neat and labelled diagram of an electric bell and describe its working.

Q19) THe incomplete diagram of an electric bell is given in the figure. Complete the diagram and the label it’s different parts

Q20) What is a declination? Draw a diagram to show the angle between the declination and true direction of geographic north/

Q21) Define the term current.

Q22) Name four appliances which work using electricity

Q23) Name two sources of electricity.

Q24) What is a battery?

Q25) What is an electric circuit?

Q26) Describe an experiment to show that electricity flows only if the circuit is complete and it does not flow if the circuit is incomplete.

Q27) You are provided with a torch bulb, a cell and two plastic-coated f metal wires. Draw a diagram to show a complete circuit to light the bulb.

Q28) In which of the following case the bulb will glow:

1. Only one terminal of a cell is joined with a metal wire to one terminal of the bulb.

2. Both terminal of the bulb is joined with two metal wires to one terminal of the cell.

3. One terminal of the cell is joined to one terminal of the bulb and other terminal of the cell to the other terminal of the bulb.

Q29) Distinguish between conductors and insulators of electricity. Give reasons

Q30) Select conductors and insulators from the following:

Glass, silver, copper, wood, paper, pure water, impure water, aluminium, iron, leather, plastic, steel, human body and ebonite.

Q31) The following diagram shows four circuits A, B, C and D. Each circuit has a cell and a torch bulb. Name the circuits in which the bulb will glow? Give reason to your answer.

Q32) The diagram given below shows a bulb connected with a cell having terminals A and B. Mark the direction of current in the bulb.

Q33) State the function of each of the following in an electric circuit and draw its symbolic representation: Switch and Cell

Q34) Draw a circuit diagram for a bulb connected to a cell with a switch. Mark arrow in the diagram to indicate the direction of flow of current.

Q35) In which arrangement are the appliances connected in the electric circuit of out homes, Series or parallel? Give reasons

Q36) State two precautions that you must take when switching on an electric circuit.