Class 10 Science Chapter 11 Practice Question Answers - Electricity

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Numericals

2. A particle with a charge of 1.5 coulombs is taken from point A at a potential of 50V to another point B at a potential of 120V. Calculate the work done.

3. How many electrons are required to get 1C of negative charge?

4. Calculate the current in a wire if 900C of charge passes through it in 10 minutes.

5. How much current will flow through a resistor of resistance 12W if a battery of 18V is connected across it?

6. Calculate the resistance of a copper wire of length 1m and the area of cross-section 2 mm². The resistivity of copper is 1.7 × 10 ^-8 W m.
7. A copper wire has a resistance of 0.5 W. Another copper wire of the same mass as the first one is double in length of the first. Find the resistance of the second wire.

8. Find the current supplied by the cell in the circuit shown in fig.

9. When a potential difference of 20 V is applied across a resistor, it draws a current of 3A. If 30V is applied across the same resistor, what will be the current?

10. How will the resistance of a wire change if its diameter (d) is doubled, its length remains the same?

11. Calculate the potential difference across each resistor in the circuit shown in the figure.

12. Three identical bulbs are connected in parallel with a battery. The current drawn from the battery is 6A. If one of the bulb gets fused, what will be the total current drawn from the battery?

13. A uniform wire of resistance R is cut into three equal pieces, and these pieces are joined in parallel. What is the resistance of the combination?

14. Consider the circuit shown in the figure. The voltmeter on the left reads 10V and that on the right reads 8V. Find (a) The current through the resistance R, (b) the value of R, and (c) the potential difference across the battery.

15. Three resistors of reistances 10W, 20W and 30 are connected in parallel with a 6V cell. Find (a) The current through each resistor, (b) the current supplied by the cell, and (c) the equivalent resistance of the circuit.

16. Consider the circuit shown in Fig. Calculate the current through the 3W resistor.

17. When two resistors are joined in series, the equivalent resistance is 90W. When the same resistors are joined in parallel, the equivalent resistance is 20W. Calculate the resistance of the two resistors.

18. (a) How will you join three resistors of resistance 4W, 6W and 12W to get an equivalent resistance of 8W.

(b) What would be the highest and the lowest equivalent resistances possible by joining these resistors?
19. How many bulbs of resistance 6 ohms should be joined in parallel to draw a current of 2 amperes from a battery of 3 volts?

20. A current of 4A passes through a resistance of 100W for 15 minutes. Calculate the heat produced in calories.

21. A 12V battery is connected to a bulb. The battery sends a current of 2.5A through it. Calculate

(a) the power delivered to the bulb, and (b) the energy transferred to the bulb in 5 minutes.

22. A current is passed through a resistor for some time. It produces 400 cal of heat in this period. If the current is doubled, how much heat will be produced for the same duration?

23. Calculate the wattage of an electric heater that draws 5A current when connected to a 220V power supply.

24. A bulb draws 24W when connected to a 12V supply. Find the power if it is connected to a 6V supply.
 (Neglect resistance change due to unequal heating in the two cases.)

25. Two identical resistance R are connected in series with a battery of potential difference V for time t. The resistor are later connected in parallel and the same battery is connected across the combination for time t. Compare the heat produced in the two cases.

26. A bulb is rated 40W, 220V. Find the current drawn by it when connected to a 220V supply.

27. A bulb is rated 60W, 240V. Calculate its resistance when it is on. If the voltage drops to 192V, what will be the power consumed and the current drawn?

28. A room has two tube lights, a fan and a TV. Each tube light draws 40W, the fan draws 80W, and the TV draws 60W. On average, the tube lights are kept on for five hours, the fan for twelve hours, and the TV for eight hours every day. The rate for electrical energy is Rs. 3.10 per kWh. Calculate the cost of electricity used in this room in a 30-day month.

29. When a particle of charge 10mC is brought from infinity to a point P, 2.0 mJ of work is done by the external forces. What is the potential at P?

30. Calculate the work done in taking a charge of 0.02C from A to B if the potential at A is 20V, and that at B is 30 V.

Answers of the Numericals

1. 0.06 J   2. 105 J   3. 6.25 × 10¹⁸ electrons   4. 1.5 A   5. 1.5 A 6. 8.5 × 10⁻³ Ω   7. 2.0 Ω   8. 1.5 A   9. 4.5 A   10. Resistance becomes 1/4th   11. 1 V, 1.5 V, 2.5 V   12. 4 A   13. R/9   14. 2 A, 5 W, 18 V   15. 5.5 W   16. 1.33 A   17. 30 Ω, 60 Ω   18. (a) Combination of 4 Ω and (6 || 12), (b) Highest: 22 Ω, Lowest: 2 Ω   19. 4 bulbs   20. 3.4 × 10⁵ cal   21. 30 W, 9000 J   22. 1600 cal   23. 1100 W   24. 6 W   25. Heat ratio: 2:1   26. 2/11 A   27. 38.4 W, 0.2 A   28. Rs. 171.12   29. 200 V   30. 0.2 J