Science Previous year Question Electricity Class 10

1. Write S.I. unit of resistivity.

 2. What is meant by electric current? Name and define its SI unit. In a conductor electrons are flowing from B to A. What is the direction of conventional current? Give justification for your answer. 

3. What is meant by electrical resistivity of a material? Derive its S.I. unit. Describe an experiment to study the factor on which the resistance of a conducting wire depends. 

4. (a) Write two points of difference between electric energy and electric power. (b) Out of 60 W and 40 W lamps, which one has higher electrical resistance when in use. (c) What is the commercial unit of electric energy? Convert it into joules. 

5. State Ohm’s law. Write the necessary conditions for its validity. How is this law verified experimentally? What will be the nature of graph between potential difference and current for a conductor? Name the physical quantity that can be obtained from this graph. 

6. Name a device that helps to maintain a potential difference across a conductor. 

7. Define 1 volt. Express it in terms of SI unit of work and charge calculate the amount of energy consumed in carrying a charge of 1 coulomb through a battery of 3 V. 

8. Two wires A and B are of equal length and have equal resistance. If the resistivity of A is more than that of B which wire is thicker and why? 

9. (a) Define electric power. Express it in terms of potential difference V and resistance R. (b) An electrical fuse is rated at 2 A. What is meant by this statement? (c) An electric iron of 1 kW is operated at 220 V. Find which of the following fuses that respectively rated at 1 A, 3 A and 5 A can be used in it.

 10. Write relation between heat energy produced in a conductor when a potential difference V is applied across its terminals and a current I flows through for ‘t’ 

11. State difference between the wire used in the element of an electric heater and in a fuse wire. 

12. An electric bulb of resistance 200Ω draws a current of 1 Ampere. Calculate the power of the bulb the potential difference at its ends and the energy in kWh consumed burning it for 5h. 

13. (a) Calculate the resistance of 1 km long copper wire of radius 1 mm. Resistivity of the copper is 1.72 x 10-8 Ω m. (b) Draw a schematic diagram of a circuit consisting of a battery of 4 cells of 2V each connected to a key, an ammeter and two resistors of 2 Ω and 3 Ω respectively in series and a voltmeter to measure potential difference across 3 Ω. 

14. How much current will an electric bulb draw from 220 V source if the resistance of the bulb is 1200Ω? If in place of bulb, a heater of resistance 100 Ω is connected to the sources, calculate the current drawn by it. 

15. Two identical wires one of nichrome and other of copper are connected in series and a current (I) is passed through them. State the change observed in the temperatures of the two wires. Justify your answer. State the law which explains the above observation. 

16. How is an ammeter connected in a circuit to measure current flowing through it? 

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

18. A given length of a wire is doubled on itself and this process is repeated once again. By what factor does the resistance of the wire change? 

19. A 9Ω resistance is cut into three equal parts and connected in parallel. Find the equivalent resistance of the combination. 

20. An electric iron has a rating of 750 W, 220 V. Calculate the (i) current flowing through it, and (ii) its resistance when in use. 

21. The charge possessed by an electron is 1.6 X 10-19 coulombs. Find the number of electrons that will flow per second to constitute a current of 1 ampere. 

22. Explain the role of fuse in series with any electrical appliance in an electric circuit. Why should a fuse with defined rating for an electric circuit not be replaced by one with a larger rating?

23. A torch bulb is rated 2.5 V and 750 mA. Calculate (i) its power, (ii) its resistance and (iii) the energy consumed, if this bulb is lighted for four hours. 

24. Series arrangements are not used for domestic circuits. List any three reasons. 

25. Two devices of rating 44 W, 220 V and 11 W, 220 V are connected in series. The combination is connected across a 440 V mains. The fuse of which of the two devices is likely to burn when the switch is ON? Justify your answer. 

26. Two resistors of 10 Ω and 15 Ω are connected in series to a battery of 6 V. How can the values of current passing through them be compared? 

27. What is an electric circuit? Distinguish between an open and a closed circuit.

28. Two resistors with resistances 5Ω and 10 Ω are to be connected to a battery of emf 6 V so as to obtain: (i) minimum current (ii) maximum current (a) How will you connect the resistances in each case ? (b) Calculate the strength of the total current in the circuit in the two cases. 

29. Two resistors of 10 Ω and 15 Ω are connected in series to a battery of 6 V. How can the values of current passing through them be compared? 

30. A wire of resistance 20 Ω is bent to form a closed square. What is the resistance across a diagonal of the square? 

31. A piece of wire of resistance 20 Ω is drawn out so that its length is increased to twice its original length. Calculate the resistance of the wire in the new Situation. 

32. (a) Define the term ‘coulomb’. (b) State the relationship between the electric current, the charge moving through a conductor and the time of flow. Calculate the charge passing through an electric bulb in 20 minutes if the value of current is 200 mA. 

33. Show how would you join three resistors, each of resistance 9  so that the equivalent resistance of the combination is (i) 13.5 Ω (ii) 6 Ω? 

34. (a) List the factors on which the resistance of a conductor in the shape of a wire depends. (b) Why are metals good conductors of electricity whereas glass is a bad conductor of electricity ? Give reason. (c) Why are alloys commonly used in electrical heating devices ? Give reason. 

35. If the potential difference across the two ends of a conductor is 5 V and the current through it is 0·2 A, then what is the resistance of the conductor ? 

36. `Define the following and Write It’s SI unit? (a) Electric current (b)Electric potential difference (c)Resistance (d) Electric power (e) Electric energy 

37. Two resistances of 4 Ω and 8 Ω are connected in parallel. What would be the combined resistance of the system? 

38. How much work is done in moving a charge of 3 coulumb from a point at the volts 115 to a point at 125 volts? 

39. Derive the formula of resistance connected in Series Connection. 

40. Derive the formula of resistance connected in parallel Connection.