Riphah International University Medical Entry Physics Electronics Set 2

Riphah International University Medical Entry Physics Electronics — Set 2

Question 1
Q1. A sinusoidal voltage of peak value 10 V is applied to a diode and a 1 kΩ resistor in series. What is the peak current?
- A) 10 mA
- B) 0 A
- C) 5 mA
- D) 20 mA
Answer: 10 mA
Explanation: Peak current = peak voltage / resistance = 10 V / 1 kΩ = 10 mA. Diode is forward biased.
Question 2
Q2. A transistor has a current gain of 50. If the base current is 20 μA, what is the collector current?
- A) 1 mA
- B) 0.5 mA
- C) 1.5 mA
- D) 2 mA
Answer: 1 mA
Explanation: Collector current = current gain * base current = 50 * 20 μA = 1 mA.
Question 3
Q3. A capacitor of 100 nF is connected in parallel with a resistor of 1 kΩ. What is the impedance at a frequency of 1 kHz?
- A) 1591 Ω
- B) 1000 Ω
- C) 796 Ω
- D) 500 Ω
Answer: 796 Ω
Explanation: Xc = 1 / (2πfC) = 1591 Ω. Z = (R * Xc) / sqrt(R^2 + Xc^2) = 796 Ω.
Question 4
Q4. A full-wave rectifier is used to rectify an AC voltage of rms value 12 V. What is the average DC output voltage?
- A) 10.8 V
- B) 12 V
- C) 15.3 V
- D) 8.5 V
Answer: 10.8 V
Explanation: Vrms = 12 V, Vpeak = 12 * sqrt(2) = 16.97 V. Vdc = 0.637 * Vpeak = 10.8 V.
Question 5
Q5. A logic gate produces an output of 1 only when both inputs are 1. What type of gate is it?
- A) AND
- B) OR
- C) NOT
- D) XOR
Answer: AND
Explanation: AND gate produces 1 only when both inputs are 1.
Question 6
Q6. A silicon diode has a voltage drop of 0.7 V when forward biased. What is the voltage drop across the diode when a 5 V battery is connected in series with the diode and a 1 kΩ resistor?
- A) 0.7 V
- B) 5 V
- C) 4.3 V
- D) 0 V
Answer: 0.7 V
Explanation: Voltage drop across diode remains 0.7 V as it is forward biased.
Question 7
Q7. A transistor amplifier has a voltage gain of 100. If the input voltage is 10 mV, what is the output voltage?
- A) 1 V
- B) 0.1 V
- C) 10 V
- D) 0.01 V
Answer: 1 V
Explanation: Output voltage = voltage gain * input voltage = 100 * 10 mV = 1 V.
Question 8
Q8. A circuit consists of a 10 kΩ resistor and a 100 nF capacitor in series. What is the time constant?
- A) 1 ms
- B) 0.1 ms
- C) 10 ms
- D) 100 ms
Answer: 1 ms
Explanation: Time constant = RC = 10 kΩ * 100 nF = 1 ms.
Question 9
Q9. A half-wave rectifier is used to rectify an AC voltage of peak value 20 V. What is the peak inverse voltage?
- A) 20 V
- B) 10 V
- C) 40 V
- D) 0 V
Answer: 20 V
Explanation: Peak inverse voltage = peak value of AC voltage = 20 V.
Question 10
Q10. A NAND gate produces an output of 0 when
- A) both inputs are 0
- B) both inputs are 1
- C) one input is 0 and the other is 1
- D) both inputs are 1 or one input is 0 and the other is 1
Answer: both inputs are 1
Explanation: NAND gate produces 0 only when both inputs are 1.
Question 11
Q11. A Zener diode is used as a voltage regulator. If the Zener voltage is 5 V, what is the output voltage?
- A) 5 V
- B) 10 V
- C) 0 V
- D) Variable
Answer: 5 V
Explanation: Output voltage = Zener voltage = 5 V.
Question 12
Q12. A common-emitter amplifier has a current gain of 50. If the base current is changed by 10 μA, what is the change in collector current?
- A) 0.5 mA
- B) 1 mA
- C) 0.1 mA
- D) 5 mA
Answer: 0.5 mA
Explanation: Change in collector current = current gain * change in base current = 50 * 10 μA = 0.5 mA.
Question 13
Q13. A filter circuit is used to remove AC ripples from a rectified voltage. What type of filter is commonly used?
- A) Capacitor filter
- B) Inductor filter
- C) LC filter
- D) RC filter
Answer: Capacitor filter
Explanation: Capacitor filter is commonly used to remove AC ripples.
Question 14
Q14. A logic circuit has three inputs A, B, and C. The output is 1 when A and B are 1 or when C is 1. What is the logic gate?
- A) AND
- B) OR
- C) XOR
- D) Combination of AND and OR
Answer: Combination of AND and OR
Explanation: The output is 1 when A and B are 1 (AND operation) or when C is 1 (OR operation), so it's a combination of AND and OR.
Question 15
Q15. A transistor has a base current of 20 μA and a collector current of 1 mA. What is the emitter current?
- A) 1.02 mA
- B) 1 mA
- C) 0.98 mA
- D) 2 mA
Answer: 1.02 mA
Explanation: Emitter current = collector current + base current = 1 mA + 20 μA = 1.02 mA.
Question 16
Q16. A diode is used to rectify an AC voltage. What is the purpose of the diode?
- A) To amplify the voltage
- B) To regulate the voltage
- C) To convert AC to DC
- D) To filter the voltage
Answer: To convert AC to DC
Explanation: Diode is used to convert AC to DC (rectification).
Question 17
Q17. A voltage regulator is used to regulate an input voltage of 12 V to an output voltage of 5 V. What is the type of regulator?
- A) Step-up regulator
- B) Step-down regulator
- C) Linear regulator
- D) Switching regulator
Answer: Step-down regulator
Explanation: Output voltage (5 V) is less than input voltage (12 V), so it's a step-down regulator.
Question 18
Q18. A circuit consists of a 1 kΩ resistor and a 100 nF capacitor in series. What is the cutoff frequency?
- A) 1591 Hz
- B) 1000 Hz
- C) 796 Hz
- D) 500 Hz
Answer: 1591 Hz
Explanation: Cutoff frequency = 1 / (2πRC) = 1591 Hz.
Question 19
Q19. A digital circuit has four inputs. What is the minimum number of NAND gates required to implement the circuit?
- A) 4
- B) 5
- C) 6
- D) It depends on the specific circuit
Answer: It depends on the specific circuit
Explanation: The number of NAND gates required depends on the specific digital circuit.
Question 20
Q20. A transistor amplifier has an input resistance of 1 kΩ and an output resistance of 10 kΩ. What is the voltage gain?
- A) 10
- B) 100
- C) 50
- D) It depends on the current gain
Answer: It depends on the current gain
Explanation: Voltage gain depends on current gain and resistance gain.