# Electrical Engineering Questions and Answers

### 21. The heat produced in a conductor of resistance 4.2 Ω with 10 A flowing in it is

(i) 42 cal/sec
(ii) 100 cal/sec
(iii) 4.2 cal/sec
(iv) 420 cal/sec

(i) 250 W
(ii) 500W
(iii) 200 W
(iv) 400 W

(i) 25/4 W
(ii) 225/4 W
(iii) 325/4 W
(iv) 125/4 W

### 24. An electric fan and a heater are marked as 100 W,220 V and 1000W, 220 V respectively. The resistance of heater is

(i) zero
(ii) greater than that of fan
(iii) less than that of fan
(iv) equal to that of fan

(i) 20 Ω
(ii) 10 Ω
(iii) 40 Ω
(iv) 5 Ω

(i) 2 cal/sec
(ii) 1 cal/sec
(iii) cal/sec
(iv) 4 cal/sec

(i) 1500
(ii) 15000
(iii) 15
(iv) 150

### 28. The water in an electric kettle begins to boil in 15 minutes after being switched on. Using the same main supply, should the length or wire used as heating element be increased or decreased if water is to be boiled in 10 minutes ?

(i) increased
(ii) decreased
(iii) unchanged
(iv) none of above

### 29. A constant voltage is applied between the two ends of a metallic wire of uniform area of cross-section. Some heat is developed. The heat is doubled if

(i) both length and radius are halved
(ii) both length and radius are doubled
(iii) the radius of wire is doubled
(iv) the length of wire is doubled

(i) H
(ii) nH
(iii) n2H
(iv) H/n2

(i) 10 W
(ii) 30 W
(iii) 90 W
(iv) 10/3 W

(i) 0.1 Ω
(ii) 12 Ω
(iii) 6 V
(iv) 3 Ω

(i) 100 J/s
(ii) 200 J/s
(iii) 50 J/s
(iv) 150 J/s

(i) 0.5A
(ii) 0.1 A
(iii) 1 A
(iv) 5 A

### 35. What is immaterial for a fuse ?

(i) its resistivity
(iii) its length
(iv) none of above

(i) 1%
(ii) 4%
(iii) 2%

(iv) 8%

### 37. Appliances based on heating effect of current work on

(i) d.c. only
(ii) a.c. only
(iii) both d.c. and a.c.
(iv) none of above

(i) 25 Ω
(ii) 250 Ω
(iii) 125 Ω
(iv) 12.5 Ω

### 39. One heater coil boils certain amount of water in 10 minutes and another heater coil in 15 minutes. In how much time the same water will be boiled if the two heaters are put in series.

(i) 12.5min
(ii) 25min
(iii) 2.5min
(iv) none of above