# 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

(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

(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

(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

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

(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

(i) n2Ro
(ii) Ro/n2
(iii) nRo
(iv) n3Ro

### 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 Ti 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.