Ques.61. In a 25kVA, 2000/200V transformer the iron and full load copper losses are 350W and 400W respectively. Calculate the value of maximum efficiency.
- 99.3%
- 97.3%
- 95.3%
- 91.6%
Ques.62. For a sheet with resistivity ρ, width w, length l, and thickness y, the resistance per square (sheet resistance) Rs is
- ρ/y
- ρy
- ρl/y
- ρ
Ques.63. Which statement is incorrect for Oil Circuit Breaker?
- It forms an explosive mixture with air.
- In this, dielectric strength reduces due to absorption of moisture.
- Needs oil replacement due to carbonization of oil
- Used in the 11KV panel in grid station
Ques.64. In dielectric heating normal voltage required is –
- 3 KV
- 8 KV
- 12 KV
- 10 KV
Ques.65. According to Einstein’s relationship for a semiconductor, the ratio of the diffusion constant to the mobility of the charge carriers is
- Variable and is twice the volt equivalent of the temperature
- Constant and is equal to the volt equivalent of the temperature
- Equal to the two and is twice the volt equivalent of the temperature
- Equal to one and is equal to the volt equivalent of the temperature
Ques.66. The ratio of the charges stored by two metallic spheres raised to the same potential is 6. The ratio of the surface area of the sphere is
- 6
- 12
- 18
- 36
Ques.67. A bipolar junction transistor with forward current transfer ratio α = 098, when working in CE mode provides current transfer ratio β as.
- 98
- 0.02
- 49
- 0.49
Ques.68. In spot welding process maximum power required is –
- 100 KVA
- 150 KVA
- 200 kVA
- 250 KVA
Ques.69. A permanent magnet moving coil ammeter is connected in 50 Hz a.c circuit in which 5 A current is flowing. If the meter remains connected in the circuit for some time,
- Meter pointer gives full-scale time,
- Meter pointer starts oscillating
- Meter coil is burnt
- None of above
Ques.70. In appliances an automobile which material is used to produce shiny appearance during electroplating
- Gold
- Silver
- Chromium
- Steel