MDCAT Physics Easy Questions

MDCAT Physics Easy Questions

1. Question 1

   Q1. The rms value of an AC is defined as the value of that DC which produces the same heating effect in a given resistance.

   • A) Average power dissipation
   • B) Peak current
   • C) Root mean square current
   • D) Instantaneous current

   Answer: Root mean square current

   Explanation: RMS current is defined as the DC that produces the same heating effect; 'Average power dissipation' is a related concept, not the definition.

2. Question 2

   Q2. In an AC circuit, the opposition to the flow of current is called

   • A) Resistance
   • B) Reactance
   • C) Impedance
   • D) Conductance

   Answer: Impedance

   Explanation: Impedance is the total opposition to AC flow; Reactance is a component of impedance, not the total opposition.

3. Question 3

   Q3. The unit of inductance is

   • A) Henry
   • B) Farad
   • C) Ohm
   • D) Tesla

   Answer: Henry

   Explanation: Henry is the unit of inductance; Farad is the unit of capacitance, not inductance.

4. Question 4

   Q4. The power factor of an AC circuit is given by

   • A) cosφ
   • B) sinφ
   • C) tanφ
   • D) cotφ

   Answer: cosφ

   Explanation: Power factor is defined as cosφ, where φ is the phase angle between voltage and current; 'sinφ' is related to reactive power.

5. Question 5

   Q5. In an AC circuit, the voltage and current are in phase when the circuit contains only

   • A) Resistance
   • B) Inductance
   • C) Capacitance
   • D) Impedance

   Answer: Resistance

   Explanation: In a purely resistive circuit, voltage and current are in phase; 'Inductance' or 'Capacitance' causes a phase shift.

6. Question 6

   Q6. The rms value of a sinusoidally varying quantity is

   • A) 1/√2 times its peak value
   • B) 1/2 times its peak value
   • C) Equal to its peak value
   • D) √2 times its peak value

   Answer: 1/√2 times its peak value

   Explanation: For a sinusoidal quantity, rms = peak / √2; '1/2 times its peak value' is incorrect, it's 1/√2.

7. Question 7

   Q7. The power dissipated in a pure inductor or capacitor is

   • A) Maximum
   • B) Minimum
   • C) Zero
   • D) Average

   Answer: Zero

   Explanation: Pure inductors and capacitors do not dissipate real power; 'Maximum' is incorrect as they don't consume real power.

8. Question 8

   Q8. The transformer works on the principle of

   • A) Mutual induction
   • B) Self-induction
   • C) Electromagnetic induction
   • D) Mutual induction and self-induction both

   Answer: Mutual induction

   Explanation: Transformers work on the principle of mutual induction; 'Self-induction' is related but not the principle behind transformers.

9. Question 9

   Q9. In a step-up transformer, the number of turns in the secondary coil is

   • A) Less than the primary coil
   • B) Equal to the primary coil
   • C) More than the primary coil
   • D) Not related to the primary coil

   Answer: More than the primary coil

   Explanation: In a step-up transformer, the secondary coil has more turns than the primary; 'Less than the primary coil' is a step-down configuration.

10. Question 10

    Q10. A 100 Ω resistor is connected to an AC source with an rms voltage of 220 V. What is the rms current?

    • A) 1.1 A
    • B) 2.2 A
    • C) 3.3 A
    • D) 4.4 A

    Answer: 2.2 A

    Explanation: rms current = rms voltage / resistance = 220 V / 100 Ω = 2.2 A. Option A is incorrect because it is half the correct value.

11. Question 11

    Q11. An inductor has an inductance of 0.1 H and is connected to an AC source with a frequency of 50 Hz. What is the inductive reactance?

    • A) 15.7 Ω
    • B) 31.4 Ω
    • C) 62.8 Ω
    • D) 125.6 Ω

    Answer: 31.4 Ω

    Explanation: Xl = 2πfL = 2π * 50 Hz * 0.1 H = 31.4 Ω. Option A is incorrect because it is half the correct value.

12. Question 12

    Q12. A transformer has 100 turns in the primary coil and 500 turns in the secondary coil. If the primary voltage is 220 V, what is the secondary voltage?

    • A) 440 V
    • B) 880 V
    • C) 1100 V
    • D) 2200 V

    Answer: 1100 V

    Explanation: V_secondary = V_primary * (N_secondary / N_primary) = 220 V * (500 / 100) = 1100 V. Option A is incorrect because it is less than the correct value.

13. Question 13

    Q13. The rms value of an AC current is 2 A. What is the peak value of the current?

    • A) 1.414 A
    • B) 2.828 A
    • C) 4 A
    • D) 5.657 A

    Answer: 2.828 A

    Explanation: I_peak = I_rms * sqrt(2) = 2 A * sqrt(2) = 2.828 A. Option A is incorrect because it is the rms value divided by sqrt(2).

14. Question 14

    Q14. A 50 Hz AC source is connected to a 0.1 H inductor. What is the inductive reactance?

    • A) 15.7 Ω
    • B) 31.4 Ω
    • C) 62.8 Ω
    • D) 125.6 Ω

    Answer: 31.4 Ω

    Explanation: Xl = 2πfL = 2π * 50 Hz * 0.1 H = 31.4 Ω. Option A is incorrect because it is less than the correct value.

15. Question 15

    Q15. In an AC circuit, the voltage and current are in phase. What is the power factor?

    • A) 0
    • B) 0.5
    • C) 0.8
    • D) 1

    Answer: 1

    Explanation: When voltage and current are in phase, the power factor is 1. Option A is incorrect because it implies a power factor of zero, meaning no real power is consumed.

16. Question 16

    Q16. A series RLC circuit is at resonance. What is the impedance?

    • A) R
    • B) Xl
    • C) Xc
    • D) sqrt(R^2 + Xl^2)

    Answer: R

    Explanation: At resonance, Xl = Xc, so the impedance Z = R. Option B is incorrect because it is the inductive reactance, not the impedance at resonance.

17. Question 17

    Q17. The turns ratio of a transformer is 2:1. If the primary voltage is 440 V, what is the secondary voltage?

    • A) 110 V
    • B) 220 V
    • C) 440 V
    • D) 880 V

    Answer: 220 V

    Explanation: V_secondary = V_primary * (N_secondary / N_primary) = 440 V * (1/2) = 220 V. Option A is incorrect because it is half the correct value.

18. Question 18

    Q18. The rms voltage across a resistor is 100 V. What is the peak voltage?

    • A) 70.7 V
    • B) 100 V
    • C) 141.4 V
    • D) 200 V

    Answer: 141.4 V

    Explanation: V_peak = V_rms * sqrt(2) = 100 V * sqrt(2) = 141.4 V. Option A is incorrect because it results from dividing by sqrt(2).

19. Question 19

    Q19. The impedance of a series RLC circuit at resonance is 100 Ω. What is the resistance?

    • A) 50 Ω
    • B) 100 Ω
    • C) 200 Ω
    • D) 400 Ω

    Answer: 100 Ω

    Explanation: At resonance, Z = R. So, R = 100 Ω. Option A is incorrect because it is half the correct resistance.

20. Question 20

    Q20. An inductor has an inductance of 0.1 H. What is its inductive reactance at a frequency of 50 Hz?

    • A) 31.4 ohms
    • B) 3.14 ohms
    • C) 314 ohms
    • D) 0.314 ohms

    Answer: 31.4 ohms

    Explanation: Inductive reactance = 2πfL = 2 * 3.14 * 50 * 0.1 = 31.4 ohms. Option B is incorrect due to wrong calculation.