Are these Alternating Current questions free to attempt?

Yes. You can attempt every Alternating Current question on this page for free without logging in, and check the correct answer with a detailed explanation instantly.

Do I need an account to practise Alternating Current MCQs?

No account is required to attempt questions and view answers. A free account adds bookmarks, personal notes, and progress tracking.

Are these previous year NEET questions?

The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.

Alternating Current NEET Questions — Free MCQ Practice

● ● ● ● ●

An alternating current is given by the equation $i = i_{1} \cos ω t + i_{2} \sin ω t$ . The r.m.s. current is given by

A.

$\frac{1}{\sqrt{2}} (i_{1} + i_{2})$

B.

$\frac{1}{\sqrt{2}} {(i_{i} + i_{2})}^{2}$

C.

$\frac{1}{\sqrt{2}} {(i_{1}^{2} + i_{2}^{2})}^{1 / 2}$

D.

$\frac{1}{2} {(i_{1}^{2} + i_{2}^{2})}^{1 / 2}$

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

$i_{r m s} = \sqrt{\frac{i_{1}^{2} + i_{2}^{2}}{2}} = \frac{1}{\sqrt{2}} {(i_{1}^{2} + i_{2}^{2})}^{1 / 2}$

● ● ● ● ●

In an ac circuit, the current is given by $i = 5 \sin (100 t - \frac{π}{2})$ and the ac potential is V = 200 sin(100t) volt. Then the power consumption is :

A.

20 watts

B.

40 watts

C.

1000 watts

D.

0 watt

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

$P = V i \cos ϕ$

Phase difference $ϕ = \frac{π}{2} \Rightarrow P = z e r o$

● ● ● ● ●

A resistance of 20 ohms is connected to a source of an alternating potential $V = 220 \sin (100 π t)$ . The time taken by the current to change from its peak value to r.m.s value is

A.

0.2 sec

B.

0.25 sec

C.

25 × 10^–3 sec

D.

2.5 × 10^–3 sec

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

Peak value to r.m.s. value means current becomes $\frac{1}{\sqrt{2}}$ times.

$T i m e t a k e n b y t h e c u r r e n t t o r e a c h i t s p e a k v a l u e : i = i_{0} \sin 100 π t \Rightarrow i_{0} = i_{0} \sin 100 π t_{1} \Rightarrow \sin 100 π t_{1} = \sin \frac{π}{2} \Rightarrow t_{1} = \frac{1}{200} s e c T i m e t a k e n b y t h e c u r r e n t t o b e c o m e \frac{i}{\sqrt{2}} a f t e r r e a c h i n g i t s p e a k v a l u e : i = i_{0} \sin 100 π t \Rightarrow \frac{1}{\sqrt{2}} \times i_{0} = i_{0} \sin 100 π t_{2} \Rightarrow \sin 100 π t_{2} = \sin \frac{3 π}{4} \Rightarrow t_{2} = \frac{3}{400} s e c T i m e t a k e n b y t h e c u r r e n t t o c h a n g e f r o m i t s p e a k v a l u e t o r . m . s . v a l u e : t_{2} - t_{1} = \frac{3}{400} - \frac{1}{200} = \frac{1}{400} s e c = 2 .5 \times 10^{- 3} s e c .$

● ● ● ● ●

Voltage and current in an ac circuit are given by $V = 5 \sin (100 π t - \frac{π}{6})$ and $I = 4 \sin (100 π t + \frac{π}{6})$

A.

Voltage leads the current by 30°

B.

Current leads the voltage by 30°

C.

Current leads the voltage by 60°

D.

Voltage leads the current by 60°

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

Phase difference $Δ ϕ = ϕ_{2} - ϕ = \frac{π}{6} - (\frac{- π}{6}) = \frac{π}{3}$

● ● ● ● ●

An alternating current of frequency ‘f’ is flowing in a circuit containing a resistance R and a choke L in series. The impedance of this circuit is

A.

R + 2πfL

B.

$\sqrt{R^{2} + 4 π^{2} f^{2} L^{2}}$

C.

$\sqrt{R^{2} + L^{2}}$

D.

$\sqrt{R^{2} + 2 π f L}$

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

$Z = \sqrt{R^{2} + X_{L}^{2}}, X_{L} = ω L$ and $ω = 2 π f$

$∴ Z = \sqrt{R^{2} + 4 π^{2} f^{2} L^{2}}$

● ● ● ● ●

A resistance of 300 Ω and an inductance of $\frac{1}{π}$ henry are connected in series to a ac voltage of 20 volts and 200 Hz frequency. The phase angle between the voltage and current is :

A.

$\tan^{- 1} \frac{4}{3}$

B.

$\tan^{- 1} \frac{3}{4}$

C.

$\tan^{- 1} \frac{3}{2}$

D.

$\tan^{- 1} \frac{2}{5}$

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

Phase angle $\tan ϕ = \frac{ω L}{R} = \frac{2 π \times 200}{300} \times \frac{1}{π} = \frac{4}{3}$

$∴ ϕ = \tan^{- 1} \frac{4}{3}$

● ● ● ● ●

In a LCR circuit having L = 8.0 henry, C = 0.5 μF and R = 100 ohm in series. The resonance frequency in radian per second is

A.

600 radian

B.

600 Hz

C.

500 radian

D.

500 Hz

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

Resonance frequency in radian/second is

$ω = \frac{1}{\sqrt{L C}} = \frac{1}{\sqrt{8 \times 0 .5 \times 10^{- 6}}} = 500 r a d / s e c$

● ● ● ● ●

The impedance of a circuit consists of 3 ohm resistance and 4 ohm reactance. The power factor of the circuit is :

A.

0.4

B.

0.6

C.

0.8

D.

1.0

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

$Z = \sqrt{R^{2} + X^{2}} = \sqrt{4^{2} + 3^{2}} = 5$

$∴ \cos ϕ = \frac{R}{Z} = \frac{3}{5} = 0 .6$

● ● ● ● ●

The power factor of a good choke coil is:

A.

Nearly zero

B.

Exactly zero

C.

Nearly one

D.

Exactly one

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

$\cos ϕ = \frac{R}{Z}$ .

In choke coil $ϕ \approx 90 °$

So $\cos ϕ \approx 0$

● ● ● ● ●

L, C and R represent physical quantities inductance, capacitance and resistance respectively. The combination representing dimension of frequency is

A.

LC

B.

(LC)^–1/2

C.

${(\frac{L}{C})}^{- 1 / 2}$

D.

$\frac{C}{L}$

You've reached today's free limit of 20 questions. Log in to keep practising for free.

Explanation

Frequency $= \frac{1}{2 π \sqrt{L C}}$

So the combination which represents dimension of frequency is $\frac{1}{\sqrt{L C}} = {(L C)}^{- 1 / 2}$

Alternating Current MCQs for NEET — Physics Questions with Answers

Frequently Asked Questions