POWER ELECTRONICS AND DRIVES PART 06

POWER ELECTRONICS AND DRIVES PART 06

1. For a power transistor, if the forward current gain α = 0.97, then β = ?

a) 0.03
b) 2.03
c) 49.24
d) 32.33
 

Answer: d

2. The power electronics devices have a very high efficiency because
a) cooling is very efficient
b) the devices traverse active region at high speed & stays at the two states, on and off
c) the devices never operate in active region
d) the devices always operate in the active region
 

Answer: b

3. For a power transistor, which of the following relations is true?
a) Ie>Ic>Ib
b) Ib>Ic>Ie
c) Ic>Ie>Ib
d) Ie=Ib
 

Answer: a
 
4. High frequency operation of any device is limited by the
a) forward voltage rating
b) switching losses
c) thermal conductivity
d) heat Sink arrangements
 

Answer: b

5. The instantaneous power loss during the delay time of a transistor is given by
a) Ic Vce
b) Ib Vbe
c) Ic Vbe
d) Ib Vce
 

Answer: a

6. For a power transistor, the average power loss during the delay time can be given by the equation
a) Ic * Vc
b) 1/T * ∫Td (Ic Vce) dt
c) Ic * dVc/dt * T
d) 1/T * ∫(Td *Tr) (Ic Vc) dt
 

Answer: b
 
7. A 1mv of i/p gives an output of 1V, the voltage gain as such would be
a) 0.001
b) 0.0001
c) 1000
d) 100
 

Answer: c

 

8. Which of the following relations is true for a BJT?
a) Ic ≈ Ie
b) Ib ≈ Ic
c) Ie ≈ Ib
d) Ib ≈ Ie ≈ Ic 

 

Answer: a
 

9. Choose the correct statement
a) A transistor will remain on as long the the base current is applied
b) A transistor remains on after a high to low pulse is applied at the base
c) A transistor will remain on as long the the collector current is applied
d) A transistor remains on after a high to low pulse is applied at the collector
Answer: a
 

10. Let’s say that a transistor is operating at the middle of the load line, then a decrease in the current gain would
a) move the Q point up
b) move the Q point down
c) result in to & fro motion of the Q point
d) not change the Q point
Answer: b