Contents

**NEET Physics Chapter Wise Mock Test – Alternating Current**

**Question 1:
**An alternating voltage V = 30 sin 50t+40 cos 50t is applied to a resistor of resistance 10Ω. The rms value of current through resistor is

(a) 5/√2 A

(b) 10/√2 A

(c) 7/√2 A

(d) 7A

**Question 2:
**The electric current in a circuit is given by I= 3t

Here, t is in second, I is in ampere. The rms current for the period t = 0 to t = 1s is

(a) 3A

(b) 9A

(c) √3 A

(d) 3√3 A

**Question 3:
**One 10 V, bulb 60 W of is to be connected to 100 V line. The required self-inductance of induction coil will be (f = 50 Hz)

(a) 0.052 H

(b) 2.42 H

(c) 16.2 H

(d) 16.2 mH

**Question 4:
**What is the value of inductance L for which the current is maximum in a series L-C-R circuit with C = 10 μF and w= 1000 s

^{-1}?

(a) 100 mH

(b) 1 mH

(c) Cannot be calculated unless R is known

(d) 10 mH

**Question 5:
**The bandwidth of a series resonant circuit is 500 Hz and the resonant frequency is 5000 Hz. The quality factor of the circuit will be

(a) 40

(b) 20

(c) 10

(d) 5

**Question 6:
**An inductor of reactance 1Ω and a resistor of 2Ω are connected in series to the terminals of a 6 V (rms) AC source. The power dissipated in the circuit is

(a) 8 W

(b) 12 W

(c) 14.4 W

(d) 18 W

**Question 7:
**An AC circuit contains a resistance R, capacitance C and inductance L in series with a source of emf e = e

_{0}sin(ωt+Φ). The current through the circuit is maximum, when

(a) R=L=C

(b) ωL = 1/ωC

(c) ω

^{2}=LC

(d) ω=RLC

**Question 8:
**An AC source is connected with a resistance R and an uncharged capacitance C in series. The potential difference across the resistor is in phase with the initial potential difference across the capacitor for the first time at the instant (assume that, at t = 0, emf is zero)

(a) π/4ω

(b) 2π/ω

(c) π/ω

(d) 3π/2ω

**Question 9:
**In a circuit, L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45°. The value of C is

(a) 1/2πf(2πfL+R)

(b) 1/πf(2πfL+R)

(c) 1/2πf(2πfL-R)

(d) 1/πf(2πfL-R)

**Question 10:
**In the given AC circuit, when switch S is at position 1,the source emf leads current by π/6. Now, if the switch is at position 2, then

**(a) current leads source emf by π/3**

(b) current leads source emf by π/4

(c) source emf lead current by π/4

(d) None of the above

**Question 11:
**An AC circuit having supply voltage E consists of a resistor of resistance 3Ω and an inductor of reactance 4Ω as shown in the figure. The voltage across the resistance at t = π/ω is

**(a) 6.4V**

(b) 10V

(c) zero

(d) 4.8V

**Question 12:
**If the rms current in a 50 Hz AC circuit is 5 A, the value of the current 1/300 s after its value becomes zero is

(a) 5√2 A

(b) 5√(3/2) A

(c) 5/6A

(d) 5/√2A

**Question 13:
**There is a current of 20 mA through an ideal choke coil of 1.5 H when connected to 220 V, 50 H AC supply. The power consumed is

(a) zero

(b) 220x20x10

^{-3}W

(c) 220×50 W

(d) 220x20x1.5 W

**Question 14:
**A coil of inductive reactance 31Ω has a resistance of 8Ω. It is placed in series with a condenser of capacitative reactance 25Ω. The combination is connected to an AC source of 110 V. The power factor of the circuit is

(a) 0.56

(b) 0.64

(c) 0.80

(d) 0.33

**Question 15:
**A resistance is connected to a capacitor in AC and the phase difference is π/4 between and voltage. When the same resistance is connected to an inductor, phase difference becomes tan

^{-1}(2). Power factor of the circuit when both capacitor and inductor are connected to the resistance will be

(a) 1

(b) 1/√2

(c) 1/√3

(d) 1/2

**Question 16:
**By what percentage the impedance in AC series circuit should be increased, so that the power factor changes from (1/2) to (1/4) (when R is constant)?

(a) 200%

(b) 100%

(c) 50%

(d) 400%

**Question 17:
**The maximum current in the circuit, if a capacitor of capacitance 1 μF is charged to a potential of 2 V and is connected in parallel to an inductor of inductance 10

^{-3}H is

(a) √4000 mA

(b) √2000 mA

(c) √1000 mA

(d) √5000 mA

**Question 18:
**A condenser of capacitance of 2.4 μF is used in transmitter to transmit at λ wavelength. If the inductor of 10

^{-8}H is used for resonant circuit, then value of λ is

(a) 292 m

(b) 400 m

(c) 334 m

(d) 446 m

**Question 19:
**

**Direction (Q.Nos.20-22):** In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements mark the correct answer as

(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion

(b) If both Assertion and Reason are true but the Reason is not correct explanation of the Assertion

(c) If Assertion is true but Reason is false

(d) If both Assertion and Reason are false

**Question 20:
Assertion (A): **The capacitor blocks DC but allows AC.

**The capacitor offers infinite resistance to DC.**

Reason (R):

Reason (R):

**Question 21:
Assertion (A): **In a series R-L-C circuit the voltage across resistor, inductor and capacitor are 8 V, 16 V and 10 V, respectively. The resultant emf in the circuit is 10 V.

**Resultant emf of the circuit is given by the relation,**

Reason (R):

Reason (R):

**Question 22:
Assertion (A): **A sinusoidal AC current flows through a resistance R. If the peak current is l0, then the power dissipated is Rl

^{2}

_{0}/2

**For purely resistive circuit, power factor cosΦ= 1.**

Reason (R):

Reason (R):

**Question 23:
**An AC ammeter is used to measure current in a circuit. When a given direct current passes through the circuit, the AC ammeter reads 3 A. When another alternating current passes through the circuit, the AC ammeter reads 4A. Then, the reading of this ammeter. If DC and AC flow through the circuit simultaneously, is

(a) 3A

(b) 4A

(c) 7A

(d) 5A

**Question 24:
**If an electron revolves in the path of a circle of radius of 0.5 x10

^{-10}m at frequency of 5×10

^{15}cycles. The electric current in the circle is

(Charge of an electron = 1.6 x 10

^{-19}C)

(a) 0.4 mA

(b) 0.8 mA

(c) 1.2 mA

(d) 1.6 mA

**Question 25:
**Through which of the AC circuit elements both the emf and current are in phase?

(a) lmpedance

(b) Inductive reactance

(c) Capacitive reactance

(d) Resistance

**Question 26:
**A resistance R draws power P when connected to an AC source. If an inductance is now placed in series with the resistance, such that the impedance of the circuit becomes Z, the power drawn will be

**Question 27:
**A transformer having efficiency, of 90% is working on 200 V and 3 kW powers supply. If the current in the secondary coil is 6 A, the voltage across the secondary coil and the current in the primary coil respectively are

(a) 300 V, 15 A

(b) 450 V, 15 A

(c) 450 V, 13.5 A

(d) 600 V, 15 A

**Question 28:
**

**Question 29:
**In a L-C-R series circuit, the potential difference between the terminals of the inductance is 60 V, between the terminals of the capacitor is 30 V and that across the resistance is 40 V. Then, supply voltage will be equal to

(a) 50 V

(b) 70 V

(c) 130V

(d) 10 V

**Question 30:
**As given in the figure, a series circuit connected across a 200 V, 60 Hz line consists of a capacitor of capacitive reactance 30Ω, a non-inductive resistor of 44Ω, and a coil of inductive reactance 90Ω and resistance 36Ω. The power dissipated in the coil is

**(a) 320W**

(b) 176W

(c) 144W

(d) 0W

**Question 31:
**A spherical drop of capacitance 1 μF is broken into eight drops of equal radius. Then, the capacitance of each small drop is

(a) 1/2 μF

(b) 1/4 μF

(c) 1/8 μF

(d) 8 μF

**Question 32:
**In the capacitor of capacitance C, charge Q and energy W is stored. If charge is increased upto 2Q, the energy stored will be

(a) W/4

(b) W/2

(c) 2W

(d) 4W

**Question 33:
**In an electrical circuit R,L,C and an AC voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and the current in the circuit is π/3. If instead, C is removed from the circuit, the phase difference is again π/3. The power factor of the circuit is

(a) 1/2

(b) 1/√2

(c) 1

(d) √3/2

**Question 34:
**

**Question 35:
**If, emf E =4cos1000t volt is applied to an L-R circuit of inductance 3 mH and resistance 4Ω, the amplitude of current in the circuit is

(a) 4/√7 A

(b) 1.0A

(c) 4/7 A

(d) 0.8A

**Question 36:
**An AC voltage is applied to a resistance R and an inductor L in series. If R and the inductive reactance are both equal to 3Ω, the phase difference between the applied voltage and the current in the circuit is

(a) π/4

(b) π/2

(c) zero

(d) π/6

**Question 37:
**A transmitter transmits at a wavelength of 300 m. A condenser of capacitance 2.4 μF is being used. The value of the inductance for the resonant circuit is approximately.

(a) 10

^{-4}H

(b) 10

^{-6}H

(c) 10

^{-8}H

(d) 10

^{-10}H

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