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NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12 PDF Download

2024

Q1: In an ideal transformer, the turns ratio is NP / NS = 1/2. The ratio VS : VP is equal to (the symbols carry their usual meaning) :
(a) 1 : 2
(b) 2 : 1
(c) 1 : 1
(d) 1 : 4        [2024]
Ans:
(b)
An ideal transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. The primary coil (with NP turns) is connected to the input voltage (VP), and the secondary coil (with NS turns) delivers the output voltage (VS).
The relationship between the input (primary) voltage and output (secondary) voltage in a transformer is determined by the ratio of the number of turns in the primary coil to the number of turns in the secondary coil, expressed by the formula:
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
In this case, the given turns ratio is NP / N= 1 / 2. To find the correct expression for VS / VP, we need to invert the given ratio to reflect the relationship with respect to the voltages. This means:
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
Therefore, substituting into the voltage ratio equation:
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
This indicates that the secondary voltage (VS) is twice the primary voltage (VP). If we were to express the ratio V: VP based on this, it would be: Option B 2 : 1
This is the correct answer as it represents that, in accordance with the transformer's turns ratio, the voltage in the secondary coil is twice that in the primary coil.

Q2: A 10μF capacitor is connected to a  210V, 50 Hz source as shown in figure. The peak current in the circuit is nearly (π=3.14) :

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12(a) 0.58 A
(b) 0.93 A
(c) 1.20 A
(d) 0.35 A                [2024]
Ans:
(b)
Capacitive Reactance
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

2023

Q1: An ac source is connected in the given circuit. The value of ϕ will be : 

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

(a) 60o
(b) 90o
(c) 30o
(d) 45o
Ans: 
(d)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q2:  If Z1 and Zare the impedances of the given circuits (a) and (b) as shown in figures, then choose the correct option

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

(a) Z1 < Z2
(b) Z1 + Z2 = 20 Ω
(c) Z1 = Z2
(d) Z>Z2
Ans: 
(a)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q3: The maximum power is dissipated for an ac in a/an:
(a) resistive circuit
(b) LC circuit
(c) inductive circuit
(d) capacitive circuit
Ans:
(a)
Power dissipated is maximum of purely resistive circuit.

Q4: For very high frequencies, the effective impedance of the circuit (shown in the figure) will be:-

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12(a) 4 Ω
(b) 6 Ω
(c) 1 Ω
(d) 3 Ω
Ans:
(d)
As frequency is very high
XC ≈ 0
XL → α
Effective circuit will beNEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Effective impedance of circuit will be = 3Ω

 Q5: The magnetic energy stored in an inductor of inductance  4 μH carrying a current of  2 A is :
(a) 4 mJ
(b) 8 mJ
(c) 8 μJ
(d) 4 μJ
Ans: 
(c)
The formula for calculating the magnetic energy stored in an inductor is given by:

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

where:
E is the energy stored (in joules, J),
L is the inductance of the inductor (in henrys, H),
I is the current flowing through the inductor (in amperes, A).
Plugging the given values into the formula:

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Hence, the energy stored in the inductor is 8 μJ.

Q6: In a series LCR circuit, the inductance L is 10 mH, capacitance C is 1 μF, and resistance R is 100 Ω. The frequency at which resonance occurs is              
(a) 15.9 rad/s
(b) 15.9 kHz
(c) 1.59 rad/s
(d) 1.59 kHz
Ans:
(d)
Solution: 
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q7: A 12 V, 60 W lamp is connected to the secondary of a step-down transformer, whose primary is connected to AC mains of 220 V. Assuming the transformer to be ideal, what is the current in the primary winding?            
(a)  0.27 A
(b) 2.7 A
(c) 3.7 A
(d) 0.37 A
Ans:
(a)
Solution:
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
For ideal transformer
Pinput = Poutput 
(VI)in = 60
220 × I = 60
I = 0.27 A

Q8: An AC source is connected to a capacitor C. Due to a decrease in its operating frequency          
(a) Capacitive reactance decreases
(b) Displacement current increases
(c) Displacement current decreases
(d) Capacitive reactance remains constant
Ans:
(c)
Solution: 
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
Since ω decreasing XC will increase hence current will decrease. Also conduction current = displacement current.
Therefore displacement current will decrease.

Q9: The net impedance of the circuit (as shown in the figure) will be            
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12(a) 10√2 Ω
(b) 15 Ω
(c) 5√5
(d) 25 Ω
Ans: 
(c)
Solution:
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

2022

Q1: Given below are two statements
Statement I : In an a.c circuit, the current through a capacitor leads the voltage across it.
Statement II : In a.c circuit containing pure capacitance only, the phase difference between the current and voltage is π.
In the light of the above statements, choose the most appropriate answer from the options given below:
(a) Statement I is incorrect but Statement II is correct
(b) Both Statement I and Statement II are correct
(c) Both Statement I and Statement II are incorrect
(d) Statement I is correct but Statement II is incorrect
Ans: 
(d)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Thus statement I is correct while II is incorrect.

Q2: An inductor of inductance 2 mH is connected to a 220 V, 50 Hz ac source. Let the inductive reactance in the circuit is X1. If a 220 V dc source replace the ac source in the circuit, then the inductive reactance in the circuit is X2, Xand X2 respectively are :
(a) 0.628 Ω, infinity
(b) 6.28 Ω, zero
(c) 6.28 Ω, infinity
(d) 0.628 Ω, zero
Ans:
(d)
We know, for A.C. Source

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

For D.C. Source
The inductor behaves as a closed circuit offering no resistance at all (at steady state) as w = 0 (For D.C.)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q3: A standard filament lamp consumes 100 W when connected to 200 V ac mains supply. The peak current through the bulb will be :
(a) 2 A
(b) 0.707 A
(c) 1 A
(d) 1.414 A
Ans:
(b)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q4: A series LCR circuit with inductance 10 H, capacitance 10 µF, and resistance 50 Ω is connected to an AC source of voltage, V = 200sin(100t) volt. If the resonant frequency of the LCR circuit is  νand the frequency of the AC source is ν, then             
(a)NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
(b)  NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
(c)  NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
(d)  NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Ans: (a)
Solution:
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12 

Q5: The peak voltage of the AC source is equal to        
(a) The rms value of the AC source 
(b) √2 times the rms value of the AC source 
(c) 1/√2 times the rms value of the AC source 
(d) The value of the voltage supplied to the circuit 
Ans: (b)
Solution:
 NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

2021

Q1: A capacitor of capacitance 'C', is connected across an ac source of voltage V, given by
V = V0sinωt
The displacement current between the plates of the capacitor, would then be given by :

(a) NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

(b) NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

(c) NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

(d) NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Ans: (b)
Given, V = V0sinωt 
We know, q = CV
Now displacement current Id is given by,

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q2: An inductor of inductance L, a capacitor of capacitance C, and a resistor of resistance 'R' are connected in series to an AC source of potential difference 'V' volts as shown in Fig. Potential difference across L, C, and R is 40 V, 10 V, and 40V, respectively. The amplitude of the current flowing through the LCR series circuit is 10√2A. The impedance of the circuit is:     
(a) 4Ω

(b) 5Ω
(c) 4√2Ω
(d) 5√2Ω

Ans: (b)
Solution:

I0 = 10√2 A
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q3: A step-down transformer connected to an AC mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit?    
(a) 2 A

(b) 4 A

(c) 0.2 A

(d) 0.4 A
Ans: 
(c)
Solution:

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
Q4: A series LCR circuit containing a 5.0 H inductor, 80 μF capacitor, and 40 Ω resistor is connected to a 230 V variable frequency AC source. The angular frequencies of the source at which power transferred to the circuit are half the power at the resonant angular frequency are likely to be    
(a) 46 rad/s and 54 rad/s

(b) 42 rad/s and 58 rad/s
(c) 25 rad/s and 75 rad/s
(d) 50 rad/s and 25 rad/s
Ans: 
(a)
Solution: 

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 122020

Q1: A 40 μF capacitor is connected to a 200 V. 50 Hz ac supply. The rms value of the current on the circuit is, nearly :
(a) 2.05 A
(b) 2.5 A
(c) 25.1 A
(d) 1.7 A
Ans:
(b)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q2: A series LCR circuit is connected to an AC voltage source. When L is removed from the circuit, the phase difference between current and voltage is π/3. If instead C is removed from the circuit, the phase difference is again π/3 between current and voltage. The power factor of the circuit is :    
(a) 1.0
(b) –1.0
(c) Zero
(d) 0.5
Ans:
(a)
Solution:
When the inductor alone is removed,
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12When the capacitor alone is removed,
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12Thus, for the original circuit,
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12Power factor = cos Δϕ = R/Z = R/R = 1

2019

Q1: Which of the following acts as a circuit protection device?    
(a) Conductor
(b) Inductor
(c) Switch
(d) Fuse
Ans: 
(d)
Solution:

Fuse wire has less melting point so when excess current flows, due to heat produced in it, it melts.

Q2: A parallel plate capacitor of capacitance 20 mF is being charged by a voltage source whose potential is changing at the rate of 3 V/s. The conduction current through the connecting wires, and the displacement current through the plates of the capacitor, would be, respectively.    
(a) Zero, 60 μA
(b) 60 μA, 60 μA
(c) 60 μA, zero
(d) Zero, zero
Ans: 
(b)
Solution:

The capacitance of capacitor C = 20 mF
= 20 × 10-6 F
Rate of change of potential NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12ic = 20 × 10–6 × 3
= 60 × 10–6 A
= 60 μA
As we know id = ic = 60 mA

2018

Q1: The magnetic potential energy stored in a certain inductor is 25 mJ when the current in the inductor is 60 mA. This inductor is of inductance:    
(a) 0.138 H
(b) 138.88 H
(c) 1.389 H
(d) 13.89 H
Ans: 
(d)
Solution:

Energy stored in the inductor
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12Energy stored in the inductor
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
Q2:  In the circuit shown in the figure, the input voltage Vi is 20 V, VBE = 0, and VCE = 0. The values of IB, IC, and β are given by:
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
(a) IB = 40 µA, IC = 10 mA, β = 250
(b) IB = 25 µA, IC = 5 mA, β = 200
(c) IB = 20 µA, IC = 5 mA, β = 250
(d) IB = 40 µA, IC = 5 mA, β = 125
Ans: 
(d)
Solution:

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
Q3: An inductor 20 mH, a capacitor 100 μF, and a resistor 50 Ω are connected in series across a source of emf, V = 10 sin 314 t. The power loss in the circuit is    
(a) 0.79 W
(b) 0.43 W
(c) 2.74 W
(d) 1.13 W
Ans: 
(a)
Solution:

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
Q4: Figure shows a circuit that contains three identical resistors with resistance R = 9.0 Ω each, two identical inductors with inductance L = 2.0 m Heach, and an ideal battery with emf ε = 18 V. The current 'i' through the battery just after the switch closed is: 

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
(a) 0.2 A
(b) 2 A
(c) 0 ampere
(d) 2 mA
Ans:
(b)
Solution:

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 122016

Q1: Which of the following combinations should be selected for better tuning of an L-C-R circuit used for combination ?
(a) R = 20 Ω, L = 1.5 H, C = 35 μF
(b) R = 25 Ω, L = 2.5 H, C = 45 μF
(c) R = 15 Ω, L = 3.5 H, C = 30 μF
(d) R = 25 Ω, L = 1.5 H, C = 45 μF
Ans:
(c)
Quality factor of an L-C-R circuit is given by,

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

As Q3 is maximum of Q1, Q2, Q3, and Q4. Hence, option (c) should be selected for better tuning of an L-C-R circuit. 

Q2: The potential differences across the resistance, capacitance and inductance are 80 V, 40 V and 100 V respectively in an L-C-R circuit. The power factor of this circuit is
(a) 0.4
(b) 0.5
(c) 0.8
(d) 1.0
Ans:
(c)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q3: A 100 Ω resistance and a capacitor of 100 Ω reactance are connected in series across a 220 V source. When the capacitor is 50% charged, the peak value of the displacement current is
(a) 2.2 A
(b) 11 A
(c) 4.4 A
(d) 11√2 A
Ans: 
(a)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Peak value of displacement current = Maximum conduction current in the circuit

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Q4: An inductor of 20 mH, a capacitor of 50 μF and a resistor. 40Ω are connected in series across a source of emf V = 10 sin 340 t. The power loss in the A.C. circuit is    
(a) 0.89W
(b) 0.51W
(c) 0.67W
(d) 0.76W
Ans: 
(b)
Solution:

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
Q5: A small signal voltage V(t) = V0 sinωt is applied across an ideal capacitor C :    
(a) Current I(t), leads voltage V(t) by 180 degree
(b) Current I(t), lags voltage V(t) by 90 degree
(c) Over a full cycle the capacitor C does not consume any energy from the voltage source.
(d) Current I(t) is in phase with voltage V(t)
Ans: 
(c)
Solution:

A capacitor does not consume energy effectively over full cycles.

Q6: 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 :
(a) P
(b)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
(c)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
(d)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
Ans: (b)
Solution:

A resistance R draws power P when connected to an AC source.
The magnitude of voltage of the AC source is
V2 = RP
∴ V=  NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

An inductor of inductance L and reactance ωL is now placed in series with the resistance

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

2015

Q1: A series R-C circuit is connected to an alternating voltage source. Consider two situations :
(a)  When capacitor is air filled.
(b)  When capacitor is mica filled.
Current through resistor is I and voltage across capacitor is V then
(a) ia > ib
(b) Va = Vb
(c) Va < Vb
(d) Va > Vb
Ans:
(d)

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

For series R – C circuit, capacitive reactance,

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

Current through resistor, i = Current in the circuit

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12

When mica is introduced capacitance will increase, hence voltage across capacitor gets decrease.

2014

Q1: A transformer having an efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6A, the voltage across the secondary coil and the current in the primary coil respectively are :  
(a) 450 V, 13.5 A
(b) 600 V, 15 A
(c) 300 V, 15 A
(d) 450 V, 15 A

Ans: (d)
Solution:
Initial power = 3000 W
As the efficiency is 90%, then the final power
NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
That is,

NEET Previous Year Questions (2014-2024): Alternating Current | Physics Class 12
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FAQs on NEET Previous Year Questions (2014-2024): Alternating Current - Physics Class 12

1. What is alternating current (AC)?
Ans. Alternating current (AC) is an electric current that reverses direction periodically. It is commonly used in household appliances and power distribution systems.
2. How does AC differ from direct current (DC)?
Ans. AC changes direction periodically, while DC flows in one direction only. AC is used for long-distance power transmission, whereas DC is commonly used in electronic devices.
3. What is the frequency of AC in India?
Ans. The frequency of AC in India is 50 Hz.
4. How is AC voltage measured?
Ans. AC voltage is measured using a device called a voltmeter, which is connected across the source of the AC power.
5. What is the significance of impedance in AC circuits?
Ans. Impedance in AC circuits is the total opposition to the flow of alternating current. It includes resistance, capacitance, and inductance, affecting the flow of current in the circuit.
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