## IMPORTANT QUESTIONS FOR CLASS 10 SCIENCE - ELECTRICITY

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**1 mark Questions**

**1.**How is ammeter connected in a circuit to measure current flowing through it?

**2.**How is voltmeter connected in a circuit?

**3.**Name a device which helps to maintain a potential difference across a conductor?

**4.**What happens to resistance of a conductor when its area of cross section is increased?

**5.**Write the S.I. unit of Resistivity?

**6.**Mention two reasons why tungsten is used for making filaments of electric lamps?

**7.**Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference, the ratio of heat produced in series and parallel combination would be

I) 1:2 ii)
2:1
iii)
1:4 iv) 4:1

**8.**Which uses more energy a 250 watt TV set in one hour or a 1200 watt toaster in 10 minutes?

**9.**Name the type of current used in household supply?

**10.**Name the type of current supplied by cell or battery.

**11.**What is the function of Rheostat?

**12.**Calculate the number of joules in 1 kilowatt hour?

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**2 or 3 marks Questions**

**1.**Should the resistance of ammeter be low or high? Give reason.

**2.**A current of 0.5 ampere is drawn by a filament of an electric bulb for 10 minutes. find the amount of charge that flows through the circuit?

**3.**How much work is done in moving a charge of 2 coulombs across two points having a potential difference of 12 volt?

**4.**How much energy is given to each coulomb of charge passing through a 6 volt battery?

**5.**Will current flow more easily through a thick wire or a thin wire of the same material when connected to the same source? Why?

**6.**Why are coils of electric toaster and electric iron made of an alloy rather than pure metal?

**7.**How much current will be an electric bulb draw from a 220 volt source if the resistance of the bulb filament is 1200 Ohm?

**8.**A wire of given material having length L and area of cross - section A has a resistance of 4 ohm. what would be the resistance of another wire of the same material having length L/ 2 and area of cross section 2A?

**9.**State the difference between the wire used in the elements of an electric heater and in fuse wire?

**10.**Calculate the potential difference between two terminals of battery, if 100 joule of work is required to transfer 20 coulomb of charge from one terminal of battery to another?

**11.**Calculate the charge passing through an electric bulb in 20 minutes if the value of current is 200 mA.

**12.**A piece of wire of resistance 20 ohm is drawn out so that its length is increased to twice its original length calculate the resistance in new situation?

**13.**Draw a closed circuit diagram consisting of 0.5 m long nichrome wire xy, an ammeter, a voltmeter, 4 cells of 1.5 volt each and a plug key.

**14.**What would be the value of V/I ratio when the potential difference is 0.8 volt ,1.2 volt and 1.6 volt respectively? What conclusion do you draw from these values?

**15.**Calculate the resistance of 1 km long wire of copper of radius 1 mm. Resistivity of copper is 1.72 x 10

^{-8}?

**16.**The resistance of a wire of 0.01 cm radius is 10 ohm, if the resistivity of the material of wire is 50 x 10

^{-8}

_{.}Find the length of the wire?

**17.**The resistance of a wire of length 250 m is 1 Ohm. If the resistivity of the material of wire is 1.6 x 10

^{-8}, find the area of cross section of the wire. How much does the resistance change if the diameter is doubled?

**18.**Calculate -

**i)**total resistance of circuit

**ii)**total current

**Iii)**amount of charge passing through the battery in 10 seconds

**19.**An electric heater of resistance 8 ohm draws 15 ampere from the service mains for 2 hours. Calculate the rate at which heat is developed in the heater.

**20.**What is cost of running an A.C. with average power of 1000 watt for 8 hours for 30 days. The cost of electric energy is 4.7 per kilowatt hour.

**21.**How many 176 ohm resistors are required to carry 5 ampere on a 220 volt line.

**22.**Find the minimum rating of fuse that can be safely used on a line on which two 1.1 kilowatt, electric geysers are to run simultaneously. The supply voltage is 220 volt.

**23.**Explain what is the difference between a direct current and alternating current ? write one advantage of using alternating current.

**24.**An air conditioner of 2 kilowatt is used in an electric circuit having a fuse of 10 ampere rating if the potential difference of the supply is 220 volt, will the fuse be able to withstand when the air conditioner is switched on? Justify your answer.

**5 Marks Questions**

**1.**In a conductor, electrons are flowing from B to A. What is the direction of conventional current? A steady current of 1 A flows through a conductor. Calculate the number of Electrons that flow through any section of the conductor for 1 second.

**2.**List two distinguishing features between the Resistance and Resistivity of a conductor. A wire is stretched so that its length becomes 6/5 times of its original length. If its original resistance is 25 â„¦, Find the new resistance and resistivity.

**3.**How many 40 W, 220 V lamps can be safely connected to a 220 V, 5 A line? Justify your answer.

**4.**A 3 â„¦ resistor and a 6 â„¦ resistor are connected in parallel combination across a 1.5 V cell. Calculate the current in –

**(i)**3 â„¦ resistance

**(ii)**6 â„¦ resistance

**(iii)**The cell

**(iv)**Calculate the Resistance of parallel combination.

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