Electricity class 10 (Question Bank)

Electricity (Question Bank)

1) `6 × 10^17` electrons cross through an area per minute. What is the electric current? (Ans `1.6 × 10^{-3} `A)

2) Calculate the current in a wire if 900 C of charge passes through it in 10 minutes.  (Ans 1.5 A)

3) `10^20` electrons pass from a point A towards another point B in 0.1 s. Calculate the current. (Ans 160 A). 

4) How many electrons pass through a conductor in 0.2s if the current passing through it is 0.5A? ( Ans `6.25 × 10^17`).

5) How much work will be done in bringing a charge of 5.0 millicoulombs from infinity to a point P at which the potential is 12 V? (Ans 0.06 J)

6) When a particle of charge 10 `\mu`C 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? (Ans 200 V)

7) How much charge flows through a wire in 10 minutes if the current through it is 2.5 A? (Ans 1500 C)

8) Calculate the work done in taking a charge of 0.02 C from A to B. if the potential at A is 20 V, and that at B is 30 V. (Ans 0.2 J) 

9) A negative charge released from a point `A` moves along line `AB`. The potential at `A` is 15 V, and it varies uniformly along `AB`. The potential at `B`

a)  may be 10 V

b) may be  15 V

c)  may be 20 V

d) must be 15 V

10) A charge is taken from a point `A` to a point `B`. The work done per unit charge in the process is called

a) the potential at `A`

b) the potential at `B`

c) the potential difference between `B` and `A`

d)  the current from `A` to `B`

11) Joule / Coulomb is same as

a) watt

b) volt

c) ampere

d) ohm

12) An electron released from rest at a point `A` moves towards a nearby point `B`. The potential at `A` is higher than the potential at `B`. (True / False). 

13) A 2V cell is connected to a 1 `\Omega` resistor. How many electrons come out of the negative terminal of the cell in 2minutes?

14) The amount of charge passing through a cell in 4 seconds is 12 C. What is the current supplied by the cell?

15) When a 24 V battery is connected to a resistor, the current in it is 0.4 A. What is the resistance of the resistor? What would be the current through it when it is connected to a battery of 6V?

16) A current of 1 A is drawn by a filament of an electric bulb. The number of electrons passing through a cross-section of the filament in 16 seconds would be roughly

a) `10^20`

b) `10^16`

c) `10^18`

d) `10^23`

17) Which of the following represents voltage?

a) Work done / current × time

b) Work done × Charge

c) Work done × Time / Current

d) Work done × Charge × Time

18) A student carries out an experiment and plots the V-I graph of three samples of nichrome wire with resistances `R_ 1, R _2, and R_3` respectively.  Which of the following is true?

(a) `R_1 = R_2 = R_3`

(b) `R_1 > R_2 > R_3`

(c) `R_3 > R_2 > R_1`

(d) `R_2 > R_3 > R_1`

19) Resistance of a metal wire of length 1 m is 26 `\Omega` at 20°C. If the diameter of the wire is 0.3 mm, what will be the resistivity of the metal at that temperature? 

20) A wire of given material having length `l` and area of cross-section A has a resistance of 4 `\Omega`. What would be the resistance of another wire of the same material having length `l/2` and area of cross-section `2A`?

21) A copper wire has diameter 0.5 mm and resistivity of `1.6 × 10^{–8}  \Omega m`. What will be the length of this wire to make its resistance 10 `\Omega`? How much does the resistance change if the diameter is doubled?

22) A cell, a resistor, a key, and an ammeter are arranged as shown in the circuit diagrams of Figure. The current recorded in the ammeter will be

a) maximum in (i)

b) maximum in (ii)

c) maximum in (iii)

d) the same in all the cases

23) Electrical resistivity of a given metallic wire depends upon

a) its length

b) its thickness

c) its shape

d) nature of the material

24) A child has drawn the electric circuit to study Ohm’s law as shown in Figure. His teacher told that the circuit diagram needs correction. Study the circuit diagram and redraw it after making all corrections

25) Three resistors each of resistance 12 `\Omega` are connected in parallel. What is the equivalent resistance?

26) Uniform wire of resistance `R` is cut into two equal pieces, and these pieces are joined in parallel. What is the resistance of the combination?

27) You have three resistors of 9 `\Omega` each. By combining them what can be (a) the highest resistance, and (b) the lowest resistance? (c) How can you combine them to get a resistance of 12`\Omega`? 

28) How will you join the resistors of resistances `3\Omega, 6 \Omega`, and `8 \Omega` to get an equivalent resistance of `10 \Omega`?

29) Find (a) the equivalent resistance, (b) the current passing through the cell, and (c) current passing through the `30 \Omega` resistor in the circuit shown in Fig. 

30) Find the current supplied by the cell in the circuit shown in Fig.

31) In the circuit shown below, calculate the total resistance of the circuit and the current flowing through it. 

32) Figure shows a part of an electric circuit. The reading of an ammeter is `3.0 A`. Find the currents through the `10 \Omega` and `20 \Omega`. 

33) What is the maximum resistance which can be made using five resistors each of `1/5 \Omega`?

34) What is the minimum resistance which can be made using five resistors each of `1/5 \Omega`?

35) Draw a circuit diagram of an electric circuit containing a cell, a key, an ammeter, a resistor of `2 \Omega` in series with a combination of two resistors (`4 \Omega` each) in parallel and a voltmeter across the parallel combination. Will the potential difference across the `2 \Omega` resistor be the same as that across the parallel combination of `4 \Omega` resistors? Give reason

36) An electric lamp, whose resistance is `20 \Omega`, and a conductor of `4 \Omega`  resistance are connected to a 6 V battery. Calculate (a) the total resistance of the circuit, (b) the current through the circuit, and (c) the potential difference across the electric lamp and conductor.

37) If in Fig. `R_1 = 10 \Omega, R_2 = 40 \Omega, R_3 = 30 \Omega, R_4 = 20 \Omega, R_5 = 60 \Omega`, and a 12 V battery is connected to the arrangement. Calculate (a) the total resistance in the circuit, and (b) the total current flowing in the circuit. 

38) An electric lamp of `100 \Omega`, a toaster of resistance `50 \Omega`, and a water filter of resistance `500 \Omega` are connected in parallel to a `220 V` source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?

39) A piece of wire of resistance `R` is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is `R^'`, then the ratio `R/R^'` is ..............

40) Several electric bulbs designed to be used on a `220 V` electric supply line, are rated `10 W`. How many lamps can be connected in parallel with each other across the two wires of `220 V` line if the maximum allowable current is `5 A?`

41) Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to the electric mains supply. What current is drawn from the line if the supply voltage is 220 V?

42) An electric heater of resistance 8 W draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.

43) An electric iron of resistance 20 W takes a current of 5 A. Calculate the heat developed in 30 s.

44) An electric iron consumes energy at a rate of 840 W when heating is at the maximum rate and 360 W when the heating is at the minimum. The voltage is 220 V. What are the current and the resistance in each case?

45) Compute the heat generated while transferring 96000 coulombs of charge in one hour through a potential difference of 50 V.

46) An electric iron of resistance 20 W takes a current of 5 A. Calculate the heat developed in 30 s.

47) Why does the cord of an electric heater not glow while the heating element does?

48) An electric bulb is connected to a 220 V generator. The current is 0.50 A. What is the power of the bulb?

49) An electric refrigerator rated 400 W operates 8 hour/day. What is the cost of the energy to operate it for 30 days at Rs 3.00 per kW h?

50)  What determines the rate at which energy is delivered by a current?

51) An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.

52) Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?

53) Which circuit shows the correct and safe positions for the fuse and the switch?

Ans: A

54. ) A conducting wire carries `10^21` electrons in 4 minutes. What is the current flowing through the wire?

(a) 40 A

(b) 7 A 

(c) 4 A 

(d) 0.7 A 

Ans:  (d)

55. In order to move a charge of 3 C between two points on a conducting wire, 12 J of work is done. How much increase or decrease in the voltage will increase the work done on the same amount of charge to 36 J? 

(a) `-12 V` 

(b) `-8 V` 

(c) `+8 V` 

(d) `+12 V`

Ans: (c)

56. What is the relationship between resistance and current?

(a) They are directly related to each other. 

(b) They are inversely related to each other. 

(c) The resistance has a greater magnitude than the current. 

(d) The current has a greater magnitude than resistance.

Ans: (b)

57. Find out the following in the electric circuit given in Figure.

(a) Effective resistance of two 8 Ω resistors in the combination 

(b) Current flowing through 4 Ω resistor 

(c) Potential difference across 4 Ω resistance 

(d) Power dissipated in 4 Ω resistor (e) Difference in ammeter readings, if any

58. `B_1 , B_2 and B_3`  are three identical bulbs connected as shown in Figure . When all three bulbs glow, a current of 3A is recorded by the ammeter A.

(i) What happens to the glow of the other two bulbs when the bulb `B_1`  gets fused?

(ii) What happens to the reading of `A_1 , A_2 , A_3`  and `A` when the bulb `B_2`  gets fused?

(iii) How much power is dissipated in the circuit when all the three bulbs glow together?

References

1. NCERT Science Class 10
2. NCERT Exemplar Science Class 10