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Free download in PDF Class 12 Physics Chapter 7 Alternating Current Induction Multiple Choice Questions and Answers for Board, JEE, NEET, AIIMS, JIPMER, IIT-JEE, AIEE and other competitive exams. MCQ Questions for Class 12 Physics with Answers were prepared based on the latest exam pattern. These short solved questions or quizzes are provided by Gkseries. These will help the students for preparation of their examination./p>
(1)
When an AC voltage of 220 V is applied to the capacitor C
[A]
the maximum voltage between plates is 220 V.
[B]
the current is in phase with the applied voltage.
[C]
the charge on the plates is not in phase with the applied voltage.
[D]
power delivered to the capacitor is zero.
Answer: power delivered to the capacitor is zero.
(2)
For an LCR circuit, the power transferred from the driving source to the driven oscillator is P = I²Z cos Φ. Which of the following is incorrect?
[A]
Here, the power factor cos Φ ≥ 0, P ≥ 0.
[B]
The driving force can give no energy to the oscillator (P = 0) in some cases.
[C]
The driving force cannot syphon out (P < 0) the energy out of oscillator.
[D]
The driving force can take away energy out of the oscillator.
Answer: The driving force can take away energy out of the oscillator.
(3)
As the frequency of an ac circuit increases, the current first increases and then decreases. What combination of circuit elements is most likely to comprise the circuit? [NCERT Exemplar]
[A]
Inductor and capacitor.
[B]
Resistor and inductor.
[C]
Resistor and capacitor.
[D]
Inductor only.
Answer: Inductor and capacitor.
(4)
The output of a step-down transformer is measured to be 24 V when connected to a 12 watt light bulb. The value of the peak current is
[A]
1/√2 A.
[B]
√2A.
[C]
2 A.
[D]
2√2 A.
(5)
An inductor of reactance 1 Ω and a resistor of 2 Ω are connected in series to the terminals of a 6 V (rms) a.c. source. The power dissipated in the circuit is
[A]
8 W.
[B]
12 W.
[C]
14.4 W.
[D]
18 W.
(6)
Which of the following combinations should be selected for better tuning of an LCR circuit used for communication?
[A]
R = 20, L= 1.5 H, C = 35 μF.
[B]
R = 25 , L = 2.5 H, C = 45 μF.
[C]
R = 15 , L = 3.5 H, C = 30 μF.
[D]
R = 25 , L = 1.5 H, C = 45 μF.
Answer: R = 15 , L = 3.5 H, C = 30 μF.
(7)
To reduce the resonant frequency in an LCR series circuit with a generator
[A]
the generator frequency should be reduced.
[B]
another capacitor should be added in parallel to the first.
[C]
the iron core of the inductor should be removed.
[D]
dielectric in the capacitor should be removed.
Answer: another capacitor should be added in parallel to the first.
(8)
When a voltage measuring device is connected to AC mains, the meter shows the steady input voltage of 220 V. This means
[A]
input voltage cannot be AC voltage, but a DC voltage.
[B]
maximum input voltage is 220V.
[C]
the meter reads not v but < v² > and is . calibrated to read √< v² > .
[D]
the pointer of the meter is stuck by some mechanical defect.
Answer: the meter reads not v but < v² > and is . calibrated to read √< v² > .
(9)
An alternating current generator has an internal resistance Rg and an internal reactance Xg. It is used to supply power to a passive load consisting of a resistance Rg and a reactance XL For maximum power to be delivered from the generator to the load, the value of XL is equal to
[A]
zero.
[B]
Xg.
[C]
-Xg.
[D]
Rg.
(10)
If the rms current in a 50 Hz ac circuit is 5 A, the value of the current 1/300 seconds after its value becomes zero is
[A]
5√2A
[C]
5/6 A
[D]
5√2A
(11)
The natural frequency (ca0) of oscillations in LC circuit is given by
(12)
In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit?
[A]
Only resistor
[B]
Resistor and inductor
[C]
Resistor and capacitor
[D]
Only inductor
Answer: Resistor and capacitor
(13)
In the case of an inductor
[A]
voltage lags the current by π/2
[B]
voltage leads the current by π/2
[C]
voltage leads the current by π/3
[D]
voltage leads the current by π/4
Answer: voltage leads the current by π/2
(14)
The phase relationship between current and voltage in a pure resistive circuit is best represented by
(15)
Reciprocal of impedance is
[A]
susceptance
[B]
conductance
[C]
admittance
[D]
transconductance
(16)
The power factor varies between
[A]
2 and 2.5
[B]
3.5 to 5
[C]
0 to 1
[D]
1 to 2
(17)
Average power generated in an inductor connected to an a.c. source is
[B]
LI²
[C]
zero
[D]
None of these
(18)
Alternating current cannot be measured by dc ammeter, because
[A]
ac cannot pass through ac ammeter.
[B]
ac charges direction.
[C]
average value of current of complete cycle is zero.
[D]
ac ammeter will get damaged.
Answer: ac cannot pass through ac ammeter.
(19)
The line that draws power supply to your house from street has
[A]
zero average current.
[B]
220 V average voltage.
[C]
voltage and current out of phase by 90°.
[D]
voltage and current are in phase.
Answer: zero average current.
(20)
The reactance of a capacitor C is X. If both the frequency and capacitance be doubled, then new reactance will be
[A]
X
[B]
2X
[C]
4X
[D]
X/4
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