IMPOTANT MCQ ON ELECTROMAGNETIC INDUCTION (TERM -1) ( FOR PSEB/ CBSE)
Q1 . The power factor for a purely capacitive circuit is :
- (a) 1
- (b) √2
- (c) 1/√2
- (d) Zero
- (d) for a capacitive circuit θ = 90° ; Power factor cosθ = cos90° = 0
Q2. Phase difference between voltage and current when an a.c. source is connected to an inductor :
- (a) 0°
- (b) 90°
- (c) 45°
- (d) 180°
- (b) 90°
Q3. Phase difference between voltage and current when an a.c. source is connected to a capacitor :
- (a) 90°
- (b) 45°
- (C) 180°
- (d) 0°
- (a) 90°
Q4. Which quantity is increased in step-down transformer ?
- (a) Resistance
- (b) Power
- (c) Current
- (d) Charge
- (c) Current, In step-down transformer, voltage decreases , current decreases.
Q5. The power in series RLC-circuit with AC source is given by :
- (a) zero
- (b) VI sinɸ
- (c) VI
- (d) VI cosɸ
- (d) VI cosɸ
Q6. The r.m.s. value of an a.c. is 5A. Its maximum value will be :
- (a) 10 A
- (b) 5√2A
- (c) 5/√2A
- (d) 5√3A
- (b) 5√2A, use I₀ = I rms√2
Q7. In LCR-circuit, the capacitance is changed from C to 4C. For the same resonance frequency, the inductance should be changed from L to :
- (a) 2L
- (b) 4L
- (c) L/2
- (d) L/4
- (d) L/4
Q8. The ratio of primary to secondary turns in an ideal transformer are 2 : 1. If the power input is P, then power output is :
- (a) 2P
- (b) P
- (C) P/2
- (d) none of these.
- (b) P, For ideal transfer input power = output power
Q9. Power dissipated in a series LCR-circuit at resonance is :
- (a) `I^{2}`R
- (b) zero
- (c) `I^{2}`⍵L
- (d) `\frac{I^{2}}{⍵C}`
- (a) `I^{2}`R
Q10.Phase difference between the voltage drop across R and C in a series LCR-circuit connected to an a.c. source is :
- (a) zero
- (b) 90°
- (c) 180°
- (d) 45°
- (b) 90°
Q11 . Power factor is one for :
- (a) pure inductor
- (b) pure capacitor
- (c) pure resistor
- (d) either an inductor or a capacitor
- (c) pure resistor
Q12. The square root of the product of inductance and capacitance has dimensions of:
- (a) length
- (b) mass
- (c) time
- (d) no dimensions.
- (c) time √LC has unit of time
Q13. In an a.c, circuit the current lags behind the voltage by π/3 the circuit contains :
- (a) only R
- (b) only L
- (c) only C
- (d) R and L both
- (d) R and L both
Q14. The power factor of LCR circuit at resonance is :
- (a) zero
- (b) 1/2
- (c) 1/√2
- (d) 1
- (d) 1
Q15. If ɸ is the phase difference between the instantaneous values of voltage V and current I in an a.c. circuit, then the average power loss over a complete cycle is:
- (a) VI sinɸ
- (b) VI cosɸ
- (c) VI
- (d) VI/2
- (b) VI cosɸ
MODEL/GUESS PAPER : 10+2 BIOLOGY MODEL QUESTION PAPER( WITH ANSWER)
GK OF TODAY
For all competition read important general knowledge questions
Q16.The values of L, C and R for a circuit are 1H, 9F and 3Ω. What is the quality factor for the circuit at resonance ?
- (a) 1
- (b) 9
- (c) 1/9
- (d) 1/3
- (c) 1/9 Using Q = `\frac{1}{R}\sqrt{\frac{L}{C}}`
Q17. In a transformer, loss due to eddy currents is minimized by :
- (a) laminating the core
- (b) laminating the core of steel
- (c) increasing the number of turns of primary coil
- (d) lubricating the core.
- (b) laminating the core of steel
Q18. An A.C. source of voltage E = 20 sin100t in connected cross a resistance 20Ω. The rms value of the current in circuit is:
- (a) 1A
- (b) 1/2A
- (c) √2A
- (d) 1/ √2A
- (d) 1/ √2A
Q19. The rate of change of current of 10 A/s in a coil produces an e.m.f. of 5 V. Then the self
inductance of the coil in henry is :
- (a) 0.5
- (b) 0.25
- (c) 1
- (d) 1.25.
- (a) 0.5
Q20. The instantaneous voltage through a device of impedance 20Ω is e = 80 sin1001t. The effective value of the current is:
- (a) 3A
- (b) 2.828 A
- (c) 1.732 A
- (d) √2A
- (b) 2.828 A
For all exam, read the gk of today
Q21 . A pure inductance coil of 30 mH is connected to an a.c. source of 220 V. The r.m.s current in the coil is :
- (a) 50.35 A
- (b) 23.4 A
- (C) 30.5 A
- (d) 12.3 A.
- (b) 23.4 A
Q22. An LCR series circuit is at resonance. Then :
- (a) the phase difference between current and voltage is 90°
- (b) the phase difference between current and voltage is 45°
- (c) its impedance is purely resistive
- (d) its impedance is zero.
- (c) its impedance is purely resistive
Q23. An LCR series a.c. circuit is at resonance with 10 V each across L, C and R. If the resistance is halved, the respective voltages across L, C and R are :
- (a) 10 V, 10 V and 5 V
- (b) 10 V, 10 V and 10 V
- (c) 20V, 20 V and 5 V
- (d) 20 V, 20 V and 10 V
- (d) 20 V, 20 V and 10 V
Q24. In which of the following circuits the maximum power dissipation is observed?
- (a) Pure capacitive circuit
- (b) Pure inductive circuit
- (c) Pure resistive circuit
- (d) None of these
- (c) Pure resistive circuit
Q25. A capacitor :
- (a) blocks AC but provides an easy path for DC
- (b) blocks DC but provides an easy path for AC
- (c) blocks both AC and DC
- (d) offers easy path for AC and DC
- (b) blocks DC but provides an easy path for AC
Q26. When AC source is connected across series LCR combination, maximum power loss will occur when :
- (a) current and voltage are in phase
- (b) current from source is minimum
- (c) inductance is minimum
- (d) capacitance is maximum
- (a) current and voltage are in phase
Q27. A transformer works on the principle of:
- (a) self induction
- (b) electrical inertia
- (c) mutual induction
- (d) magnetic effect of the electrical current
- (c) mutual induction
