ISC Class 12 Specimen Paper 2022 Electricity and Electronics Semester 2

ISC SEMESTER 2 EXAMINATION
SPECIMEN QUESTION PAPER
ELECTRICITY AND ELECTRONICS
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Maximum Marks: 40
Time allowed: One and a half hour
Candidates are allowed an additional 10 minutes for only reading the paper.
They must NOT start writing during this time.
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Answer all questions in Section A, Section B and Section C.
The intended marks for questions or parts of questions are given in brackets. [ ]
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SECTION A - 8 MARKS

Question 1
(i) The emitter of a transistor is _____________ doped (lightly, heavily) [1]

(ii) State whether the statement given below is True or False. [1]
The value of α of a transistor is more than 1.

(iii) Define voltage gain of a Common – Emitter (CE) amplifier. [1]

(iv) With reference to Power Amplifier, what is meant by impedance matching. [1]

(v) With reference to vacuum tubes, state the importance of cathode bypass capacitor. [1]

(vi) If a triode has a mutual conductance of 1·5mA/V and plate resistance of 12KΩ, [1]
calculate its amplification factor.

(vii) The base-emitter junction of a transistor, has _____________. [1]

(a) a reverse bias

(b) a wide depletion layer

(c) low resistance

(d) low conductance

1

(viii) Output from a transistor amplifier is: [1]

(a)

(b)

(c)

(d)

SECTION B - 12 MARKS

Answer the following questions briefly.

Question 2 [2]

State any two differences between half wave rectifier and full wave rectifier.

Question 3 [2]

Draw a neat circuit diagram of an RC filter.

Question 4 [2]

With reference to transistors, obtain the relationship between α and β (symbols have their
usual meaning).

Question 5 [2]

What inference can be drawn by maintaining control grid at:

(i) Positive potential

(ii) Negative potential

Question 6 [2]

State any two advantages of Power Amplifier over Voltage Amplifier.

2

Question 7 [2]

(i) For the Common – Emitter (CE) transistor given in Figure 1(a), β=45 and voltage
drop across 1KΩ resistor which is connected to the collector circuit is 1V.
Calculate the base current of the transistor.

Figure 1(a)

OR

(ii) For the Common – base (CB) transistor given in Figure 1(b), the current
amplification factor is 0·9. If the emitter current is 1mA, calculate the base current
of the transistor.

Figure 1(b)

SECTION C - 20 MARKS

Answer the following questions.

Question 8 [4]

With the help of a neat circuit diagram, explain the working of a bridge rectifier.

Question 9 [4]

With the help of a neat circuit diagram of a Common Emitter (CE) amplifier, explain how
a weak signal can be amplified. (Use either PNP or NPN type of transistor)

3

Question 10 [4]

Figure 2 given below shows a circuit diagram of a voltage stabilizer. Explain the
importance of the following:

(i) resistor ‘R’

(ii) Zener diode

Figure 2

Question 11 [4]
𝐼
(i) Prove 𝐼𝑟𝑚𝑠 = 0
√2

OR
2𝐼
(ii) Prove 𝐼𝑑𝑐 = 𝜋𝑜

Question 12 [4]

Explain the working of a crystal microphone. Also, state the energy conversion that takes
place in this microphone.

4