20 September 2011


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. Define resistivity of material.
2. What is the power of torch bulb rated at 2.5V and 500mA?
3. Why series arrangement not used for connecting domestic electrical appliances in a circuit?
4. Which has higher resistance – a 50W bulb or a 2.5W bulb and how many times?
5. What is the direction of flow of conventional current?
6. Why is it not advisable to handle electrical appliances with wet hands?
7. Two electric bulbs marked 100W 220V and 200W 200V have tungsten filament of same length. Which of the two bulbs will have thicker filament?
8. How does the resistance of a wire vary with its area of cross section?
9. D raw the following symbols
(i) Battery (ii) Switch closed (iii) Resistor of resistance R  (iv) Voltmeter
10A. geyser is rated 1500W, 250V. This geyser is connected to 250V mains. Calculate –
i. The current drawn      ii. The energy consumed in 50hrs.
iii. The cost of energy consumed at Rs. 2.20 per kWh.
11W. hat is the function of an electric fuse? Name the material used for making fuse. In household circuit where is fuse connected?
12 Write one important advantage of using alternative current. How alternating current differ from direct current?
13What is the difference between short circuiting and overloading?
a. ) Draw diagram showing three resistors R1, R2 and R3 in series.
b) Two resistors of resistance 4W and 12W
i) In parallel  ii) In series    Calculate the values of effective resistance in each case.
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

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