Free Electronics MCQs with Answers
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A p-n junction forms when p-type and n-type semiconductor regions meet, creating a depletion layer, barrier potential and rectifying action. The work covers forward and reverse bias, junction current, diode characteristics, and how a diode converts alternating current into pulsating direct current through half-wave and full-wave rectification.
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Read the Electronics notesFree MDCAT chapter notes with key terms660 questions · page 7 of 33
- A. The number of electrons increases while that of holes decreases
- B. The number of holes increases while that of electrons decreases
- C. Number of electrons and holes remains the same
- D. Number of electrons and holes increases equally
Explanation: Due to bond cleavage, an electron-hole pair is always produced. Heating an N-type semiconductor generates equal numbers of electron-hole…
Correct answer: Number of electrons and holes increases equally- A. Both Assertion & Reason are true, and the reason explains the assertion
- B. Both Assertion & Reason are true, but the reason does not explain the assertion
- C. Assertion is true, but Reason is false
- D. Both Assertion and Reason are false
Explanation: Electrons are the majority carriers in N-type semiconductors, and they are electrically neutral, but neutrality does not explain the…
Correct answer: Both Assertion & Reason are true, but the reason does not explain the assertion- A. IE = - mA, IB = 9 mA
- B. IE = 9 mA, IB = - mA
- C. IE = 1 mA, IB = 11 mA
- D. IE = 11 mA, IB = 1 mA
Explanation: IC = 0.9 × IE, so IE = IC /0.9 = 10/0.9 ≈ 11 mA. IB = IE - IC = 11 - 10 = 1 mA.
Correct answer: IE = 11 mA, IB = 1 mA- A. 9.9
- B. 99
- C. 990
- D. 9900
Explanation: Voltage gain = β × (RL /Rin), where β = α/(1-α) = 0.99/0.01 = 99. Gain = 99 × (10/1) = 990.
Correct answer: 990- A. 36 mA
- B. 9 mA
- C. 4 mA
- D. 3.6 mA
Explanation: β = α/(1-α) = 0.9/0.1 = 9. Change in collector current ΔIC = β × ΔIB = 9 × 0.4 = 3.6 mA.
Correct answer: 3.6 mA- A. 15.114 mA
- B. 10.252 mA
- C. 2.606 mA
- D. 5.12 mA
Explanation: ΔIE = ΔIB + ΔIC. Thus, ΔIB = ΔE - ΔIC = 8.86 - 6.254 = 2.606 mA.
Correct answer: 2.606 mA- A. 1
- B. 2
- C. 3
- D. 4
Explanation: Two NAND gates are used: the first produces the negated AND, and the second inverts it to form an AND gate.
Correct answer: 2- A. T⁻¹
- B. T
- C. T²
- D. T³/²
Explanation: Thermionic emission follows the Richardson-Dushman equation, where emission current varies as T².
Correct answer: T²- A. It is used as a half-wave rectifier
- B. It is used as a shunt regulator
- C. It is used as an AC voltage stabilizer
- D. Both B and C
Explanation: Zener diodes are used for voltage regulation (shunt regulator, AC stabilizer), not as half-wave rectifiers, which use standard diodes.
Correct answer: It is used as a half-wave rectifier- A. Current and time
- B. Voltage and current
- C. Voltage and time
- D. Forward voltage and reverse current
Explanation: A diode's characteristic curve plots current versus applied voltage, showing its behavior in forward and reverse bias.
Correct answer: Voltage and current- A. An oscillator
- B. An amplifier
- C. A detector
- D. A rectifier
Explanation: A rectifier converts alternating current (AC) to direct current (DC) for devices requiring DC power.
Correct answer: A rectifier- A. Zero resistance
- B. Low resistance
- C. Infinite resistance
- D. High resistance
Explanation: In forward bias, a junction diode has low resistance, allowing current to flow easily.
Correct answer: Low resistance- A. Holes only
- B. Both electrons and holes
- C. Electrons only
- D. Bounded electron
Explanation: The potential barrier in a diode prevents the diffusion of both electrons and holes across the junction.
Correct answer: Both electrons and holes- A. Oscillator
- B. Rectifier
- C. Filters
- D. Amplifier
Explanation: Filters smooth the pulsating output voltage in rectification circuits.
Correct answer: Filters- A. Increases under forward bias
- B. Increases under reverse bias
- C. Is independent of applied voltage
- D. All of these
Explanation: Reverse bias increases the depletion region's width in a diode.
Correct answer: Increases under reverse bias- A. Two
- B. Four
- C. Three
- D. Five
Explanation: A bridge rectifier uses four diodes for full-wave rectification.
Correct answer: Four- A. Negative charge
- B. No free charge
- C. Positive charge
- D. Positive ions
Explanation: The depletion region has no free charge carriers due to the recombination of electrons and holes.
Correct answer: No free charge138. The single germanium or silicon crystal formed after adding a pentavalent impurity is known as:
- A. Semiconductor
- B. N-type substance
- C. P-N substance
- D. P-type substance
Explanation: Adding a pentavalent impurity to silicon or germanium creates an N-type semiconductor with free electrons from the fifth valence electron.
Correct answer: N-type substance- A. Minority carriers
- B. Holes
- C. Majority carriers
- D. Electrons
Explanation: Forward current in a diode is driven by majority carriers (electrons in N-type, holes in P-type) moving across the junction.
Correct answer: Majority carriers- A. Full wave rectified
- B. No rectification and has the same peak value in the positive and negative half cycles
- C. No rectification and has different peak values during positive and negative half cycles
- D. Half wave rectified
Explanation: The direction of current is opposite through R for positive and negative half cycles, so the output is not rectified.
Correct answer: No rectification and has the same peak value in the positive and negative half cycles