Electrical Test Questions and Answers

21. The resistance of a straight conductor is independent of

(i) temperature
(ii) material
(iii) cross-sectional area
(iv) shape of cross-section

22. A length of wire has a resistance of 6 ohms. The resistance of a wire of the same material three times as long and twice the cross-sectional area will be

(i) 36 ohms
(ii) 9 ohms
(iii) 1 ohm
(iv) 12 ohms

23. The drift velocity of electrons is of the order of

(i) 1 ms^-1
(ii) 10^-3 ms^-1
(iii)10⁶ ms^-1
(iv) 3 x 10⁸ ms^-1

24. Conductivity is the reciprocal of

(i) current density
(ii) resistance
(iii) resistivity
(iv) none of the above

25. The specific resistance of a metallic conductor with rise in temperature

(i) increases
(ii) decreases
(iii) remains unchanged
(iv) none of the above

26. The potential difference of an energy source that provides 50 mJ of energy for every micro coulomb of charge that flows is

(i) 5 V
(iii) 500V
(ii) 50 V
(iv) 50kV

27. Insulators have temperature co-efficient of resistance

(i) zero
(ii) positive
(iii) negative
(iv) none of above

28. Eureka has ………. temperature co-efficient of resistance.

(i) almost zero
(ii) negative
(iii) positive
(iv) none of the above

29. What quantity of charge must be delivered by a battery with a potential difference of 100 V to do 500 J of work ?

(i) 5C
(ii) 0.5C
(iii) 50C
(iv) 500C

30. A piece of aluminium wire is stretched to reduce its diameter to half of its original value. Its resistance will become

(i) two times
(ii) four times
(iii) eight times
(iv) sixteen times

31. Semiconductors have temperature coefficient of resistance

(i) zero
(ii) negative
(ii) positive
(iv) none of the above

32. The thermal speed of electrons is of the order of

(i) 1 ms^-1
(ii) 10³ ms^-1
(iii) 10⁶ ms^-1
(iv) 3 x 10⁸ ms^-1

33. Constantan wire is used for making standard resistance because it has

(i) low specific resistance
(ii) high specific resistance
(iii) negligibly small temperature co-efficient of resistance
(iv) high melting point

34. The resistance of a material 2 m long and 2 m² in area of x-section is 1.6 x 10⁸ Ω. Its specific resistance will be

(i) 16 x 10^-8
(ii) 6.4 x 10^-8
(iii) 3.2 x10^-8
(iv) 0.16 x 10^-8

35. The SI unit of conductivity is

(i) ohm-m
(ii) ohm/m
(iii)mho-m
(iv) mho/m

36. The value of α (temperature co-efficient of resistance) depends upon

(i) length of the material
(ii) X-sectional area of the material
(iii) volume of the material
(iv) nature of the material and temperature

37. A copper wire of resistance R_o is stretched till its length is increased n times of its original length. Its resistance now will be

(i) n²R_o
(ii) R_o/n²
(iii) nR_o
(iv) n³R_o

38. The resistivity of a material is 2 x 10^-8 Ωm. What will be the resistance of a hollow pipe of the material of length 1 m and having inner and outer radii 10 cm and 20 cm respectively ?

(i) 2 x 10^-4 Ω
(ii) 2.1 x 10^-7 Ω
(iii) 3 x 10^-5 Ω
(iv) 2.82 x 10^-3 Ω

39. A piece of aluminium (Al) and germanium (Ge) are called from T_i K to T₂ K. The resistance of

(i) each of them increases
(ii) each of them decreases
(iii) aluminium increases and that of germanium decreases
(iv) aluminium decreases and that of germanium increases.

40. At 0 K, germanium behaves as

(i) a conductor
(ii) an insulator
(iii) a superconductor
(iv) a ferromagnetic substance.