# class 12 physics objective Alternating Current Pdf final hot question

## class 12 physics objective Alternating Current Pdf

बिहार बोर्ड इंटर परीक्षा 2022 के सभी विद्यार्थी के सभी विषय की सभी प्रकार के प्रश्न का प्रारूप और PDF वर्ग नोट विषयवार सभी प्रकार के study note ( MCQ , Short question long question )

Bihar Board Class 10 & 12 Science all subject Note and PDF

1. Alternating voltage (V) is represented by the equation
(a) V(t) = Vmeωt
(b) V(t) = Vmsin ωt
(c) V(t) = Vm cot ωt
(d) V(t) = Vm tan ωt

1. The rms value of potential difference V shown in the figure is 1. The phase relationship between current and voltage in a pure resistive circuit is best represented by  class 12 physics objective Alternating Current Pdf

1. In the case of an inductor
(a) voltage lags the current by π2
(b) voltage leads the current by π2
(c) voltage leads the current by π3
(d) voltage leads the current by π4

1. Which of the following graphs represents the correct variation of inductive reactance XLwith frequency u? 1. In a pure capacitive circuit if the frequency of ac source is doubled, then its capacitive reactance will be
(a) remains same
(b) doubled
(c) halved
(d) zero

1. Which of the following graphs represents the correct variation of capacitive reactance Xc with frequency v u? 1. 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

1. 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

1. In series LCR circuit, the phase angle between supply voltage and current is 1. In a series LCR circuit the voltage across an inductor, capacitor and resistor are 20 V, 20 V and 40 V respectively. The phase difference between the applied voltage and the current in the circuit is
(a) 30°
(b) 45°
(c) 60°
(d) 0°

1. At resonance frequency the impedance in series LCR circuit is
(a) maximum
(b) minimum
(c) zero
(d) infinity

1. At resonant frequency the current amplitude in series LCR circuit is
(a) maximum
(b) minimum
(c) zero
(d) infinity

1. Quality factor and power factor both have the dimensions of
(a) time
(b) frequency
(c) work
(d) angle

1. The natural frequency (ca0) of oscillations in LC circuit is given by 1. A transformer works on the principle of
(a) self induction
(b) electrical inertia
(c) mutual induction
(d) magnetic effect of the electrical current

1. For an ideal-step-down transformer, the quantity which is constant for both the coils is
(a) current in the coils
(b) voltage across the coils
(c) resistance of coils
(d) power in the coils

1. In an LCR series ac circuit, the voltage across each of the components L, C and R is 50 Volt. The voltage across LC combination is :

(A) 50 Volt

(B) 25 Volt

(C) 100 Volt

(D) 0 Volt

1. The phase difference between current and voltage in an AC circuit is θ. Then power factor will be:

(A) cosθ

(B) sinθ

(C) tanθ

(D) 1 θ

1. The working principle of choke coil is based on

(A) Conservation of angular momentum

(B) Self induction

(C) Mutual induction

(D) Conservation of momentum

1. In a step up transformer the number of coils in primary coils is N1 and N2 in secondary. Then :-

(A) NI = N2

(B) NI < N2

(C) NI > N2

(D) None of these

1. The device that increases AC voltage is called –

(A) resistor

(B) step-down transformer

(C) step-up transformer

(D) transformer

1. The oscillation frequency of an LC circuit is f. If both the capacitance and inductance be doubled, the frequency will become –

(A) f / 4

(B) 2f

(C) 4f

(D) f / 2

1. In LCR-circuit, L = 8.0 H, C = 0.5 μF, and R = 100 Ω are connected in series. The resonant frequency will be

(C) 600 hertz

(D) 500 hertz

1. A choke coil is used to control current in a circuit of

(A) ac only

(B) dc only

(C) both ac and dc

(D) None of these

1. Step-down transformer increases

(A) current

(B) voltage

(C) wattage

(D) None of these

1. The thermal effect of alternating current is practically

(A) Joule heating

(B) Peltier heating

(C) Thomson effect

(D) None of these

1. The power factor of a choke coil is about

(A) 90°

(B) 0

(C) 1

(D) 180°

1. The power factor of a condenser is

(A) 90°

(B) 1

(C) 180°

(D) 0

1. For which of the following, capacitor works as infinite resistance ?

(A) DC

(B) AC

(C) both DC and AC

(D) None of these

1. L-C circuit without AC-source is called

(A) oscillatory circuit

(B) drift circuit

(C) hysteresis circuit

(D) None of these

1. I. unit of Impedance is

(A) henry

(B) ohm

(C) tesla

(D) None of these

1. The equation of an AC is I = 60sin100πt. The root mean square value will be

(A) 60√2

(B) 60 / √2

(C) 100

(D) zero

1. The value of phase difference between current and emf in an AC circuit with resistance only, is

(A) zero

(B) π / 2

(C) π

(D) 2π

1. The unit of reactance is

(A) ohm

(C) ampere

(D) mho

1. The unit of capacitive reactance is

(B) ohm

(C) maxwell

(D) ampere

1. The impedance of L-R series circuit is

(A) R = ωL

(B) R2 + ω2L2

(C) √R2+ω2L2

(D) R

1. In LCR circuit energy loss in circuit is

(A) in inductance

(B) in resistance

(C) in condenser

(D) All of above

1. The frequency of domestic electricity supply is 50 Hz. The frequency at which current becomes zero is

(A) 25

(B) 50

(C) 100

(D) 200

1. The frequency of alternating current supply in India is

(A) 50 hertz

(B) 60 hertz

(C) 100 hertz

(D) 220 hertz

1. The conversion of electrical energy into thermal energy in a transformer is called

(A) copper loss

(B) iron loss

(C) hysterisis loss

(D) None of these

1. In A.C. circuit, the current and voltage are given by i = 5 cos wt and V = 200sin wt respectively. Power loss in the circuit

(A) 20W

(B) 40W

(C) 1000W

(D) zero