## Tuesday, 30 September 2014

### CURRENT ELECTRICITY MULTIPLE CHOICE QUESTIONS

1. In the following figure potential difference between A and B is . 0 volt 10 volt 5 volt 15 volt

2. The lead wires should have
 Larger diameter and low resistance Smaller diameter and low resistance Smaller diameter and high resistance Larger diameter and high resistance

3. What is unit for specific resistance ?. [Rugved]
 ohm/cm ohm.cm.cm ohm.cm ohm

4. A metal wire of specific resistance 64 x 10-6 Ωcm and length 198 em has resistance of 7 Ω. The radius of the wire will be
 2.4 cm 0.024 cm 0.24 cm 24 cm

5. A wire of 50 cm long and 1 mm² in cross-sectional area carries a current 4A when connected to a 2V battery. The resistivity of the wire is
 2 x 10 -7 Ωm 4 x 10 -6 Ωm 5 x 10 -7 Ωm 1 x 10 -6 Ωm
6. The current from the battery in circuit diagram shown is . 1 A 1.5 A 2 A 3 A

7. If an ammeter is to be used in place of a voltmeter the we must connect with the ammeter a
 Low resistance in parallel High resistance in series High resistance in parallel Low resistance in series

8. An unknown resistance R1 is connected in series with a resistance of 10Ω. This combination is connected to one gap of a metre bridge while a resistance R2 is connected in the other gap. The balance point is at 50 em. Now, when the 10 Ω resistance is removed the balance position shifts to 40 em. The value of R1 is (in ohm)
 10 40 20 60

9. If six identical cells each having an emf of 6 V are connected in parallel, the emf of the combination is
 1V 1/6 V 36V 6V

10. Two wires of the same dimensions but resistivities P1 and P2 are connected in series. The equivalent resistivity of the combination is
 ρ₁ + ρ₂ √ρ₁ρ₂ ρ₁ + ρ₂ / 2 2(ρ₁ + ρ₂)
11. Identify the set in which all the three materials are good conductor of electricity
 Cu, Ag, Au Cu, Hg, NaCI Cu, Si, Diamond Cu, Ge, Hg

12. At what temperature will the resistance of a copper wire become three times its value at 0°C? (Temperature coefficient of resistance for copper = 4 x 10-3 per 0C)
 400 0 c 500 0 c 450 0 c 550 0 c

13. Two wires of the same material are given. The first wire is twice as long as the second and has twice the diameter of the second. The resistance of the first will be
 Twice of the second Equal to the second Half of the second Four times of the second

14. Potential difference between the points P and Q in the electric circuit shown is. 4.5 V 2.4 V 1.1 V 2.88 V

15. In a metre bridge experiment null point is obtained at 20 em. from one end of the wire when resistance X is balanced against another resistance Y. If X < Y, then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4 X against Y
 40 cm 50 cm 80 cm 70 cm
16. There are three voltmeters of the same range but of resistances 10000 Ω, 8000 Ω and 4000 Ω respectively. The best voltmeter among these is the one whose resistance is
 10000 Ω 40000 Ω 80000 Ω None of these

17. If in the circuit shown, the internal resistance of the battery is 1.5 Ω and VP and VQ are the potentials at P & Q respectively what is the potential difference between P and Q . Zero 4 volts (VQ > VP) 4 volts (VP > VQ) 2.5 volts (VQ > VP)

18. In a typical Wheatstone network the resistances in cyclic order are A = 10 Ω, B = 10 Ω, C = 4 nand D = 4 Ω. For the bridge to be balanced. 10 Ω should be connected in parallel with A 5 Ω should be connected in series with B 10 Ω should be connected in series with A 5 Ω should be connected in parallel with B

19. The resistance of 20 em long wire is 5 ohm. The wir~ is stretched to a uniform wire of 40 em length. The resistance now will be (in ohms)
 5 20 10 200

20. If a wire of resistance R is melted and recasted to half of its length, then the new resistance of the wire will be. [KCET (Med.) 200]
 R/4 R R/2 2R

21. A cell of internal resistance 3 ohm and emf 1 volt is connected to a uniform wire of length 500 em and resistance 3 ohm. The potential gradient in the wire is
 30 mV/cm 20 mV/cm 1 mV/cm 4 mV/cm

22. Four resistances are connected in a circuit in the given figure. The electric current flowing through 4 ohm a 6 ohm resistance is respectively . 2 amp and 4 amp 1 amp and 1 amp 1 amp and 2 amp 2 amp and 2 amp

23. The resistance of a conductor is 5 ohm at 50°C and 6 ohm at 100°C. Its resistance at 0°C is
 1 ohm 3 ohm 2 ohm 4 ohm

24. The potential difference between points A and B of adjoining figure is . 2/3 V 4/3 V 8/9 V 2 V

25. Two wires A and B of same material and same mass have radius 2 r and r. If resistance of wire A is 34 Ω, then resistance of B will be
 544 Ω 68 Ω 272 Ω 17 Ω

26. Which of the following does not obey Ohm's law
 Copper Diode-valve Aluminium None of these

27. The equivalent resistance of the following diagram between A and B is. 2/4 Ω 6 Ω 9 Ω none of these

28. The resistors of resistances 2 Ω, 4 Ω and 8 Ω are connected in parallel, then the equivalent resistance of the combination will be
 8/7 Ω 7/4 Ω 7/8 Ω 4/9 Ω

29. By increasing the temperature, the specific resistance of a conductor and semiconductor
 Increases for both Increases, decreases Decreases for both Decreases for both

30. The resistivity of a wire depends on its
 Length Shape Area of cross-section Material

31. Read the following statements carefully Y: The resistivity of a semiconductor decreases with increase of temperature Z : In a conducting solid, rate of collisions between free electrons and ions increases with increases of temperature Select the correct statements (s) from the following
 Y is true but Z is false Both Y and Z are true Y is false but Z is tru

32. A uniform wire of resistance R is uniformly compressed along its length, until its radius becomes n times the original radius. New resistance of the wire becomes
 R/n⁴ R/n R/n² nR

33. The internal resistance of a cell is the resistance of
 Electrodes of the cell Electrolyte used in the cell Vessel of the cell Material used in the cell

34. A wire of resistance 10 Ω is bent to form a circle,Pand Q are points on the circumference of the circle dividing it into a quadrant and are connected to a battery of 3 V and internal resistance 1 Ω as shown in the figure. The currents in the two parts of the circle are . 6/23 A and 18/23 A 4/25 A and 12/25 A 5/26 A and 15/26 A 3/25 A and 9/25 A

35. Two resistance wires on joining in parallel, the resultant resistance is 6/5 Ω. One of the wire breaks. The effective resistance is 2 Ω. The resistance of the brokes wire was
 3/5 Ω 6/5 Ω 2 Ω 3 Ω

36. Six identical cells of emf E and internal resistance r are connected in parallel, then the net emf and internal resistance of the combination will be
 6E: 6r E,6r E,r/6 E/6,r/6

37. The resistance of a wire is R. If the length of the wire is doubled by stretching, then the new resistance will be
 2R R 4R R/4

38. Resistances of 6 ohm each are connected in the manner shown in adjoining figure. With the current ampere as shown in figure, the potential difference VP - VQ is . 3.6 V 3.0 v 6.0 v 7.2 v

39. Two resistance r1 and r2 (r1 < r2 ) are connected in parallel. Their equivalent resistance R is
 R < r1 r1 < R < ( r1 + r2) r1 < R < r2 R < ( r1 > r2)

40. An ammeter reads upto 1 ampere. Its internal resistance is 0.81 ohm. To increase the range to 10 A the value of the required shunt is
 0.09 Ω 0.3 Ω 0.03 Ω 0.9 Ω

41. In the given figure, when galvanometer shows no deflection, the current (in ampere) flowing through 5Ω resistance will be. 0.5 0.9 0.6 1.5

42. When cells are arranged in parallel
 The current capacity decreases The emf increases The current capacity increases The emf decreases

43. A uniform wire of resistance 9 n is cut into 3 equal parts. They are connected in the form of equilateral triangle ABC. A cell of emf 2V anj negligible internal resistance is connected across B and C. Potential difference across AB is
 1 V 3V 2V 0.5V

44. The internal resistance of a cell of emf 12 V is 5 x 10 -2 Ω . It is connected across an unknown resistance. Voltage across the cell, when a current of 60 A is drawn from it, is
 15 V 9 V 12 V 6 V

45. Two cells each of emf E and internal resistance r are connected parallel across a resistor R. The power dissipated in the resistor is maximum if
 R = r R = 3r/2 R = 2r R = r/2

46. If the current through 3 n resistor is 0.8 A then the potential drop through 4 Ω resistor is. 9.6 V 2.6 V 4.8 V 2.2 V

47. Three resistors are connected to form the sides of a triangle ABC, the resistance of the sides AB, BC and CA are 40 ohms; 60 ohms and 100 ohms respectively. The effective resistance between the points A and B in ohms will be. [JIPMER 2002]
 32 50 64 200

48. The resistance of a coil is 4.2 Ω at 100°C and the temperature coefficient of resistance of its material is 0.004 °C. Its resistance at Q °C is
 6.5 C 3Ω 5Ω 4Ω

49. The resistance of an incandescent lamp is
 Greater when switched off The same whether it is switched off or switched on Smaller when switched on None of these

50. The number of dry cells, each of emf 1.5 volt and internal resistance 0.5 ohm that must be joined in series with a resistance of 20 ohm so as to send a current of 0.6 ampere through the circuit is
 2 10 8 12