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Electronics and Communication Engineering - Electromagnetic Field Theory

Exercise : Electromagnetic Field Theory - Section 3
21.
When a diode is not conducting, its bias is
forward
zero
reverse
zero or reverse
Answer: Option
Explanation:

Diode conducts only when forward biased. There is no conduction when bias is zero or reverse.

22.
The SCR would be turned OFF by voltage reversal of applied anode-cathode ac supply of frequency of
30 kHz
15 kHz
5 kHz
20 kHz
Answer: Option
Explanation:

For inverter grade SCR, typical turn off time (toff) is 5 to 50 μsec while 50 to 100 μsec for converter grade SCR.

Hence supply frequency of 5 kHz will turn off the SCR by voltage reversal
because = 200 μsec.

23.
The number of valence electrons in a donor atom is
2
3
4
5
Answer: Option
Explanation:

Therefore, it can donate one electron.

24.
An electron rises through a voltage of 100 V. The energy acquired by it will be
100 eV
100 joules
(100)1.2 eV
(100)1.2 joules
Answer: Option
Explanation:

When an electron rises through 1 V, energy = 1 eV.

25.
Measurement of hall coefficient enables the determination of
mobility of charge carriers
type of conductivity and concentration of charge carriers
temperature coefficient and concentration of charge carriers
fermi level and forbidden energy gap
Answer: Option
Explanation:

Hall effect can be used to find type and concentration of charge carriers.

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