## Electricity test paper

MARKS-30

Instructions:

Questions : 1 to 5 – 1 Mark each

Questions : 6 to 9 – 2 Marks each

Questions : 10 to 13 – 3 Marks each

Question 14 – 5 Marks

1. Name the instrument used to measure electric current.

2. What is the mathematical form of Ohm‘s law?

3. Name a metal which is the best conductor electricity.

4. Why resistance become more in series combination?

5. What is electrical power? Write its unit.

6. Why does resistance of a conductor increase with increase in temperature?

7. Current in a circuit is doubles by changing resistance. What will be the change in power loss?

8. Why are the conductors of electric heating devices such as bread toaster and electric iron made of alloy rather than pure metal?

9. Draw the following symbols

i) Electric cell ii) Switch open iii) Electric bulb iv)Ammeter

10. A 100 watt electric bulb is lighted for 2 hours daily and four 40 watt bulbs are lighted for 4 hours daily. Calculate the energy consumed (in kWh) in 30 days.

11. Resistance of a conductor depends on which three factors. Explain with mathematical expression.

12. What is the effect of temperature on resistance of – pure metals, insulators and semi – conductors.

13. Write 3 points of difference between direct and alternate current.

14. a) Draw diagram showing three resistors R1, R2 and R3 in parallel.

b) Two identical resistors, each of resistance 2 ohms, are connected in turn

i) In series and

ii) In parallel

To a battery of 12 volts. Calculate the ratio of power consumed in two cases.

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