NEET UG Physics Practice Paper – Alternating Current (Set 11)

Attempt all 30 MCQs and check your score instantly.

1. RMS value of current is:

I₀/√2
I₀
√2I₀
none

2. AC current varies:

sinusoidally
linearly
constant
none

3. Frequency unit:

Hz
Volt
Ampere
Joule

4. Angular frequency:

2πf
f/2π
f²
none

5. Capacitive reactance:

1/ωC
ωL
R
none

6. Inductive reactance:

ωL
1/ωC
R
none

7. Impedance unit:

Ohm
Volt
Ampere
Watt

8. Power factor:

cosφ
sinφ
tanφ
none

9. Pure resistor phase:

0
90°
180°
none

10. Pure inductor phase:

90°
0
180°
none

11. Pure capacitor phase:

-90°
0
90°
none

12. Impedance formula:

√(R²+(XL-XC)²)
R+XL
XC
none

13. Resonance condition:

XL=XC
XL>XC
XC>XL
none

14. Resonant frequency:

1/2π√LC
√LC
LC
none

15. At resonance impedance:

minimum
maximum
zero
none

16. RMS voltage:

V₀/√2
V₀
√2V₀
none

17. Average AC over cycle:

zero
max
min
none

18. Power in AC circuit:

VI cosφ
VI
I²R
none

19. Inductor stores energy in:

magnetic field
electric field
heat
none

20. Capacitor stores energy in:

electric field
magnetic field
heat
none

21. AC generator works on:

EMI
Ohm law
current
none

22. Transformer core material:

soft iron
copper
plastic
none

23. Power factor for pure resistor:

1
0
-1
none

24. Power factor for pure inductor:

0
1
-1
none

25. Power factor for pure capacitor:

0
1
-1
none

26. LC circuit oscillation frequency:

1/2π√LC
√LC
LC
none

27. Peak current relation:

I = I₀ sinωt
I=IR
V=IR
none

28. Phase difference unit:

radian
meter
second
none

29. AC is used because:

easy transmission
cheap
stable
none

30. RMS power formula:

VI cosφ
VI
I²R
none

Submit

NEET UG Physics Notes – Alternating Current (Set 11)

Alternating Current (AC) is a very important and scoring chapter in NEET UG Physics. It focuses on circuits where current and voltage vary with time. Questions are mostly formula-based + concept-based, especially involving phase relationships, reactance, resonance, and power.

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1. Alternating Current (AC)

Alternating current is the current that changes magnitude and direction periodically.

Equation:

$$I = I_0 \sin(\omega t)$$I=I0​sin(ωt)

Where:

• $I_0$I0​ = peak current
• $\omega$ω = angular frequency

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2. Frequency and Angular Frequency

Frequency (f):

• Number of cycles per second
• Unit: Hertz (Hz)

Angular Frequency:

$$\omega = 2\pi f$$ω=2πf

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3. RMS Value (Root Mean Square)

RMS value represents the effective value of AC.$$I_{rms} = \frac{I_0}{\sqrt{2}}, \quad V_{rms} = \frac{V_0}{\sqrt{2}}$$Irms​=2​I0​​,Vrms​=2​V0​​

Importance:

• Equivalent to DC value producing same heating effect

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4. Average Value of AC

• Over a full cycle → Zero
• Because positive and negative halves cancel

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5. Reactance

Reactance is opposition offered by inductors and capacitors.

Inductive Reactance:

$$X_L = \omega L$$XL​=ωL

Capacitive Reactance:

$$X_C = \frac{1}{\omega C}$$XC​=ωC1​

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6. Impedance (Z)

Total opposition in AC circuit:$$Z = \sqrt{R^2 + (X_L – X_C)^2}$$Z=R2+(XL​−XC​)2​

Unit:

• Ohm (Ω)

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7. Phase Difference

Resistor:

• Voltage and current in phase
• Phase difference = 0°

Inductor:

• Current lags voltage by 90°

Capacitor:

• Current leads voltage by 90°

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8. Power in AC Circuit

$$P = VI \cos\phi$$P=VIcosϕ

Where:

• $\phi$ϕ = phase difference

Power Factor:

$$\cos\phi$$cosϕ

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9. Power Factor Cases

Circuit	Power Factor
Pure Resistor	1
Pure Inductor	0
Pure Capacitor	0

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10. Resonance in RLC Circuit

Condition:

$$X_L = X_C$$XL​=XC​

Resonant Frequency:

$$f = \frac{1}{2\pi \sqrt{LC}}$$f=2πLC​1​

Key Points:

• Impedance is minimum
• Current is maximum

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11. Energy Storage

Inductor:

$$U = \frac{1}{2}LI^2$$U=21​LI2

• Stores energy in magnetic field

Capacitor:

$$U = \frac{1}{2}CV^2$$U=21​CV2

• Stores energy in electric field

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12. AC Generator

Working Principle:

• Based on Electromagnetic Induction

Function:

• Converts mechanical energy into electrical energy

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13. Transformer

Principle:

• Works on mutual induction

Voltage Ratio:

$$\frac{V_p}{V_s} = \frac{N_p}{N_s}$$Vs​Vp​​=Ns​Np​​

Core Material:

• Soft iron (to reduce losses)

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14. Advantages of AC

✔ Easy transmission over long distances
✔ Can be stepped up/down using transformers
✔ Lower power loss

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15. Important NEET Formulas

• $I = I_0 \sin\omega t$I=I0​sinωt
• $\omega = 2\pi f$ω=2πf
• $X_L = \omega L$XL​=ωL
• $X_C = 1/\omega C$XC​=1/ωC
• $Z = \sqrt{R^2 + (X_L – X_C)^2}$Z=R2+(XL​−XC​)2​
• $P = VI \cos\phi$P=VIcosϕ

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16. Common Mistakes

❌ Confusing RMS and peak values
❌ Forgetting phase differences
❌ Mixing up reactance formulas
❌ Ignoring power factor

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17. Quick Revision Tips

• AC is sinusoidal
• RMS is most important for numericals
• Reactance depends on frequency
• Resonance condition is very important

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Conclusion

Alternating Current is a formula-heavy but easy scoring chapter in NEET.

Focus on:

• RMS values
• Reactance
• Impedance
• Power factor
• Resonance

👉 With strong basics, you can easily score full marks in AC questions.