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V. LEARN ACADEMY (GARKHA)

TOP 10 NUMERICALS FOR CBSE CLASS 10TH (PRACTICE SET-1, ELECTRICITY)

Previous year questions

1. There are P resistor each of resistance R. First they all are connected in series and equivalent resistance is A.Now they are connected in parallel and
   equivalent resistance is B. What is the ratio of A and B?
   (a) A:B = P²:1  (b) A:B = 1:P   (c) A:B =2:P²    (d) A:B = P³:2
2. An electric lamp of 100 Ohm, a toaster of resistance 50 Ohm, and a water filter of resistance 500 Ohm 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 must current as all three appliances and what is the current through it?
   (a) I = 5A , R = 3 Ohm (b) I = 6.0A , R = 6 Ohm
   (c) I = 7.0A , R = 4 Ohm (d) I = 7.04A , R = 31.25 Ohm
3. A student has a resistance wire of 1 ohm. If the length of this wire is 50 cm, to what length he should stretch it uniformly so as to obtain a wire of 4 Ohm resistance? Justify your answer.
   (a) 80 cm (b) 90 cm  (c) 100cm  (d) 95cm
4. Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be:
   (a) 1:2.    (b) 2:1   (c) 4:1    (d) 1:4
5. An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be:
   (a) 100 W  (b) 75 W  (c) 50 W  (d) 25 W
6. The figure below shows three cylindrical copper conductors along with their face areas and lengths.
   The figure below shows three cylindrical copper conductors along with their face areas and lengths. Compare the resistance and the resistivity of the three conductors
   Compare the resistance and the resistivity of the three conductors. Justify your answer. Ans- Rb > Ra > Rc

7. Two lamps, one rated 100 W at 220 V and the other 200 W at 220 V are connected (i) in series and (ii) in parallel to the electric main supply of 220 V. Find the current drawn in each case.                                                            (a) i) 0.50 A ii) 484/3 Ohm       (b) i) 0.30 A ii) 484/3 Ohm              (c) i) 0.40 A ii) 484 Ohm      (d) i) 0.45 A , 480 Ohm

8. The electric power consumed by a device may be calculated by either of the two expressions P = I2R or P = V2/R. The first expression indicates that it is directly proportional to R whereas the second expression indicated inverse proportionality. How can the seemingly different dependence of P on R in these expressions be explained?

9. A household uses the following electrical appliances:
i) Refrigerator of rating 400 W for ten hours each day.
ii) Two electric fans of rating 80 W each for twelve hours each day.
iii) Six electric tubes of rating 18 W each for 6 hours each day.
Predict the amount of electricity bill of the household for the month of June if the cost is Rs. 3.00/unit. (a)Rs. 591.12  (b)Rs. 981.64    (c)Rs. 555.46     (d)Rs. 667.56

10. A person carries out an experiment and thus plots the V-I graph of three taken samples of nichrome wire with different resistances R1, R2 and R3, respectively (Figure.12.5). Which one of the following is true?

(a) R1 = R2 = R3

(b) R1 > R2 > R3

(c) R3 > R2 > R1

(d) R2 > R3 > R1

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