## Thursday, 18 November 2021

### QUIZ ON ELECTROMAGNETIC INDUCTION UNIT 4 ( 10+2 PHYSICS)

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