Electricity
ASSIGNMENT
1. Fill in the blank spaces, by choosing the correct words from the list given below :
List : electric current, conducting material, conductor, cell, dynamo, power house,
hands, closed, button cell, closing, bare.
(i) The source of electric current for hand held transistor is .............................
(ii) Electricity used in homes is generated in .............................
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(iii) An electricity generating machine consists of a turbine and a .............................
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(iv) The substance which allows ...........................
.............................
to flow through it is called
(v) A closed circuit has its every part made of .............................
(vi) ............................. is the source of electricity for pocket calculator.
(vii) A bulb placed in ............................. electric circuit glows.
(viii) An electric circuit is made by ............................. switch.
(ix) We should not touch .......................... live electric wires with our ..........................
2. Write ‘T’ for true and ‘F’ for false in front of the following statements :
(i) Copper is a conductor, but plastic coating is insulator.
(ii) Switches are placed in metal casing to prevent them from breaking.
(iii) Silk thread is a good conductor of electricity.
(iv) A bulb is the source of electricity in a torch.
(v) We can light a house by using electric cells.
(vi) Electricity can kill a person.
(vii) Earth connection protects user from receiving shocks.
(viii) We should not touch switches with bare hands.
(ix) Metals are good conductors of electricity.
(x) A bulb lights up only when current flows through it.
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3. Statements given below are incorrect. Write the correct statements :
(i) Ordinary tap water does not conduct electric current.
(ii) Ebonite is good conductor of electricity.
(iii) Electricity used in homes is generated from storage cells.
(iv) Earth connection allows the excess electricity to flow into earth.
(v) The source of electricity in a flash torch is its blub.
(vi) When the path of electric current starting from one terminal to other terminal is
broken, then the electric circuit is known as closed circuit.
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(vii) In an open electric circuit, the electricity flows through all its constituting
elements.
(viii) Fuse wire is an alloy of 60% copper and 40% lead.
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(ix) In series circuit, all appliances work independently.
4. Tick (
) the most appropriate answer.
(i) In an open electric circuit :
(a) the path of electric current is completely broken.
(b) the path of electric current is not broken.
(c) the path of electric current is partially broken
(d) none of these
(ii) The path along which electric current flows, is called :
(a) electric circuit
(b) insulator
(c) conductor
(d) resistor
(iii) A fuse wire is an alloy of :
(a) lead and copper
(b) tin and aluminium
(c) lead and tin
(d) tin and copper
(iv) A fuse wire has a :
(a) very low melting point
(b) low melting point
(c) high melting point
(d) very high melting point
(v) Electric energy supplied to homes is measured by :
(a) voltmeter
(b) ammeter
(c) galvanometer
(d) kilowatt-hour meter
(vi) One unit of electric energy is equal to :
(a) one kilowatt hour
(b) one watt hour
(c) 1000 joules
(d) none of these
(vii) The device used to generate large amount of electricity, is :
(a) electric cell
(b) storage battery
(c) solar cell
(d) electric generator
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(viii) The cartridge in dry cell contains :
(a) manganese dioxide and ammonium chloride
(b) manganese dioxide and zinc dust
(c) ammonium chloride and zinc dust
(d) manganese dioxide and activated carbon
5. Find the odd one out. Give a reason for your choice.
(i) ebonite, alcohol, plastic, mercury.
(ii) copper, salt water, cotton, human body.
(iii) electric cell, storage cell, electric geyser, electric generator.
(iv) water heater, electric iron, electric toaster, tube light.
6. (i)
(ii)
(iii)
(iv)
(v)
(vi)
Name
Name
Name
Name
Name
Name
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two household electric appliances, which produce light.
four household electric appliances, which produce heat.
two office appliances, which use electricity.
two household appliances, which cause cooling effect.
two industrial appliances, which use electricity.
four appliances, which do not work with electricity.
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7. (i) Name the source of electricity for a pocket calculator.
(ii) Name four more devices which work with the source mentioned in 7(i).
8. (i) How is the electricity for household use produced on large scale?
(ii) How does the above electricity reach our homes?
9. Draw a neat and labelled diagram of simple dry cell (Leclanche cell).
10. (i)
(ii)
(iii)
(iv)
What is an electric circuit?
What do you understand by the term closed electric circuit?
What do you understand by the term open electric circuit?
An electric fan is placed in an open electric circuit. Will the fan work or not? Give
a reason for your answer.
11. (i) What is an electric socket? Draw a neat diagram of a three-pin electric socket.
(ii) What is the function of earth-pin in the socket?
12. What do you understand by the following terms? Give four examples in each case.
(i) Conductors
(ii) Insulators
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13.
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Figures (A) to (H), show an electric circuit through a cell and an electric bulb. State your
observations in each case and give one reason.
14. Pick out the conductors and insulators from the following list :
List : (i) glass, (ii) brass, (iii) ebonite, (iv) silver, (v) aluminium, (vi) syrup, (vii) gold,
(viii) steel, (ix) salt solution, (x) wool, (xi) wood, (xii) rubber, (xiii) plastic, (xiv) copper,
(xv) a rupee coin, (xvi) mica, (xvii) sulphur, (xviii) paper, (xix) air, (xx) human body.
15. A bulb is placed in an electric circuit. State two conditions which must be satisfied, if
the bulb has to light up.
16. (i) What is an electric switch?
(ii) How does an electric switch help us in household wiring?
17. (i)
(ii)
(iii)
(iv)
What is an electric fuse?
Name the metals used for making fuse wire.
How does electric fuse protect an electric circuit?
Why are miniature circuit breakers preferred to electric fuse?
18. State the advantages of household circuit in parallel.
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19. State any two ways of conserving electric energy in :
(i) Homes
(ii) Offices
(iii) Factories
20. State four precautions while using electrical appliances.
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