Physics Class 12 MCQ Alternating Current – Chapter 7

Best way to score good marks in any subject is that firstly get over of all the chapters that are scoring, and in Physics 12 ‘Alternating Current’ Chapter 7 is one suh chapter that if you revise it properly, you are definitely going to improve your marks on your score card.

In this article, we are going to help you with your revision of MCQs of Alternating Current Chapter 7 Class 12 Physics. We know that your Board exams are hovering around, and this time when they have introduced MCQs also in the pattern, then it is a plus point for all the students to score good marks.

Practice these MCQs of Alternating Current and get an idea about what type of MCQs can be asked from you. These Physics MCQs Class 12 On Alternating Current are really important from the perspective of your examination and you can score really good marks if you dedicate some time to these Alternating Current MCQs Physics Chapter 7.

Physics Class 12 MCQ Magnetism And Matter – Chapter 5

Physics Class 12 MCQ Electromagnetic Induction – Chapter 6

Physics Class 12 MCQ Alternating Current – Chapter 7

Ques 1: Choose the quantity whose SI unit is not ohm.

  • Resistance
  • Reactance
  • Capacitance
  • Impedance

Capacitance

Ques 2: The peak value of 220 V a.c. is

  • 220 V
  • 220 / √2 V
  • 440 V
  • 220 √2 V

220 √2 V

Ques 3: Which of the following does not have the dimensions of time?

  • RC
  • L / R
  • R / L
  • √LC

R / L

Ques 4: The variation of reactance of a capacitor with frequency is represented correctly by

d

 

Alternating Current Class 12 MCQs Questions with Answers

Ques 5: Phase difference between voltages across L and C in series is

  • 00
  • 900
  • 1800
  • 3600

1800

Ques 6: The resistance of a coil for direct current in 10 ohm. When a.c. sent through the same coil, its resistance would be

  • 10 Ω
  • > 10 ohm
  • <10 ohm
  • cannot say

> 10 ohm

Ques 7: The average value of a.c. voltage E = E0 sin ωt over the time interval t = 0 to t = π/ω is

  • -2 E0
  • E0
  • 2 E0 / π
  • zero

2 E0 / π

Ques 8: The alternating current from a source is represented by I = 0.5 sin 314 t. The frequency of a.c. is

  • 314 Hz
  • 100 Hz
  • 50 Hz
  • zero

50 Hz

Ques 9 Q factor of resonance is given by

  • 1/R √(L/C)
  • 1/R √(C/L)
  • 1/L √(R/C)
  • 1/C √(L/R)

1/R √(L/C)

Ques 10: The power factor of an a.c. circuit is given by cos ∅ =

  • R/Z
  • Z/R
  • R/XL
  • R/XC

R/Z

Important MCQs With Answers Alternating Current Chapter 7 Physics Class 12

Ques 11: A transformer is an electrical device used for

  • producing direct current
  • producing alternating current
  • changing d.c. into a.c.
  • changing a.c. voltages

changing a.c. voltages

Ques 12: The relation Es / Ep = ns / np is applicable only to

  • a.c. generator
  • d.c. generator
  • induction coil
  • step up/step down transformer

step up/step down transformer

Ques 13: A battery of 12 V is connected to primary of a transformer with turns ratio ns / np = 10. Voltage across secondary would be

  • 120 V
  • 1.2 V
  • 12 V
  • Zero

Zero

Ques 14: Out of the following, choose the wrong statement:

  • A transformer cannot work statement:
  • A transformer cannot work on d.c.
  • A transformer can produce a.c. power
  • In a transformer, when a.c. voltage is raised n times, te alternating current to 1/n time.

A transformer can produce a.c. power

Ques 15: In a series LR-circuit, the inductive reactance is equal to the resistance R of the circuit. An e.m.f. E = E0 cos (ωt) is applied to the circuit. The power consumed in the circuit is

    • E2v / R
    • E2v / 2R
    • E2v / 4R
    • E2v / 8R

    E2v / 2R

Ques 16: One 60 V, 100 W bulb is to be connected to 100 V, 50 Hz ac-source. The potential drop across the inductor is (f = 50 Hz)

  • 80 V
  • 40 V
  • 10 V
  • 20 V

80 V

Physics MCQs For Class 12 Chapter 7 Alternating Current

Ques 17: An AC voltage source of variable angular frequency ω and fixed amplitude V is connected in series with a capacitance C and electric bulb of resistance R (inductance zero). When ω is increased

  • The bulb glows dimmer
  • The bulb glows brighter
  • Net impedance of circuit is unchanged
  • Total impedance of circuit is unchanged

The bulb glows brighter

Ques 18: An alternating e.m.f. of angular frequency ω is applied across an inductance. The instantaneous power developed across it has an angular frequency

  • ω/4
  • ω/2
  • ω

Ques 19: In electric are furnace, Cu or Iron is melted due to variation of

  • current
  • magnetic field
  • voltage
  • electric field

magnetic field

Ques 20: When AC source is connected across series R-C combination, the ac-current may lead ac-voltage by

  • 00
  • 1800
  • 300
  • 900

300

Ques 21: High voltage transmission line is preferred as

  • Its appliances are line is preferred as
  • Thin power cables are required
  • Idle current very low
  • Power loss is very less

Power loss is very less

Ques 22: The r.m.s. voltage of the wave form shown is

  • 10 V
  • 7 V
  • 6.37 V
  • 12 V

10 V

Ques 23: In series R-L-C circuit, quality factor can be improved by

  • decreasing L
  • increasing C
  • decreasing R
  • decreasing R and L

decreasing R

Ques 24: When ac source is connected across series R-L-C combination. Maximum power loss will occur provided

  • current and voltage are in phase
  • current from source is minimum
  • inductance is minimum
  • capacitance is maximum

current and voltage are in phase

Physics MCQs Class 12 Chapter 7 – Alternating Current

Ques 25: In R-L-C series ac-circuit, impedance cannot be increased by

  • increasing frequency of source
  • decreasing frequency of sournce
  • increasing the resistance
  • increasing the voltage of the sournce

increasing the voltage of the sournce

Ques 26: In highly inductive load cirucit, it is more dangerous when

  • we close the switch
  • open the switch
  • increasing the resistance
  • decreasing the resistance

open the switch

Ques 27: In electric sub-station in township, large capacitor banks are used

  • to reduce power factor
  • to improve power factor
  • to decrease current
  • to increase current in the circuit

to improve power factor

Ques 28: In a purely resistive a.c. cirucit, the current

  • is in phase with the e.m.f.
  • leads the e.m.f. by a difference of π radians phase
  • leads the e.m.f. by a phase difference of π/2 radians
  • lags behind the e.m.f. by phase difference of π/4 radians

is in phase with the e.m.f.

Ques 29: A capacitor of capacitance C has reactance X. If capacitance and frequency become double, then the capacitative reactance will be

  • 2 X
  • 4 X
  • X/2
  • X/4

X/4

Ques 30: In a transformer the no. of turns of primary and secondary coil are 500 and 400 respectively. If 220 V a.c. is supplied to the primary coil, then ratio of currents in primary and secondary coils is

  • 4 : 5
  • 5 : 4
  • 5 : 9
  • 9 : 5

4 : 5

Physics 12 Current Electricity MCQ Question Answer – Chapter 3

We hope that you liked the collection on MCQs. these are some important MCQs Of Alternating Current Chapter 7. These Alternating Current MCQs are as per the latest pattern of the Board. Try these questions as many times as you want to and pass your Physics exam with bright colors.

Updated: October 17, 2021 — 11:57 am

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