NEET PhysicsUpdated 19 Oct 2026

Moving Charges and Magnetism: NEET PYQs and weightage

Moving Charges and Magnetism carries 4.6 of 100 Physics marks in NEET by past-paper share: 35 of the 758 tagged NEET Physics PYQs in the ViJEEta bank (NEET 2013–2026). It ranks 6 of 30 Physics chapters.

Take the 25-question Moving Charges and Magnetism test Formula sheet ↓All NEET Physics chapters

4.6/100 Weight in Physics

Exam importance (4/5, by past-paper share)

35 NEET PYQs

420 Practice questions

399 With measured difficulty

How the weight is computed: this chapter's tagged NEET PYQs divided by all tagged NEET Physics PYQs in the bank (35 of 758), times 100, with repeated questions counted once. The bank does not store the year of each NEET question, so none is printed. Computed from the bank at build time. Updated 19 Oct 2026.

Moving Charges and Magnetism: formula sheet for NEET

14 formulas, each with when to use it. Copy it onto one page of your notebook: that page is this chapter's handbook.

Magnetic force on a charge
$F = q v B sin θ$
$F = q (v \times B) (vector form)$
$F = q (E + v \times B) (with an electric field too)$
Use it when: A charge moves through $B$ . $θ$ is the angle between $v$ and $B$ . The force is $0$ if $v ∥ B$ , and it does no work.
Radius of circular path
$r = \frac{m v}{q B} = \frac{p}{q B}$
Use it when: A charge enters a uniform $B$ with $v$ perpendicular to $B$ .
Time period and frequency
$T = \frac{2 π m}{q B}$
$ν = \frac{q B}{2 π m}$
$ω = \frac{q B}{m}$
Use it when: Asked for revolution time or frequency. None of these depend on speed or radius (the cyclotron idea).
Pitch of helix
$p = v_{∥} T = \frac{2 π m v _{∥}}{q B}$
Use it when: $v$ makes an angle with $B$ . Split $v$ into a part along $B$ and a part across $B$ ; only the part along $B$ sets the pitch.
Force on a straight wire
$F = I l B sin θ$
$F = I l \times B (vector form)$
Use it when: A current-carrying rod sits in an external $B$ . For balancing against gravity, $m g = I l B$ .
Long straight wire
$B = \frac{μ _{0} I}{2 π r} (outside)$
$B = \frac{μ _{0} I r}{2 π a ^{2}} (inside a thick wire of radius a, r < a)$
Use it when: You need the field near an infinite wire. Outside, $B \propto 1/ r$ ; inside a uniform wire, $B \propto r$ .
Centre of circular coil
$B = \frac{μ _{0} N I}{2 R}$
$B = \frac{μ _{0} I}{4 R} (semicircular arc)$
Use it when: You need the field at the centre of a loop, coil or arc. Straight leads pointing at the centre add nothing.
Axis of circular loop
$B = \frac{μ _{0} I R ^{2}}{2 ( x ^{2} + R ^{2} ) ^{3/2}}$
Use it when: The point is on the axis at distance $x$ from the centre. At $x = 0$ this gives back $\frac{μ _{0} I}{2 R}$ .
Long solenoid
$B = μ_{0} n I (n = turns per metre)$
Use it when: You need the uniform field inside a solenoid. Convert total turns to turns per metre first; multiple layers add to $N$ .
Two parallel wires
$f = \frac{μ _{0} I _{1} I _{2}}{2 π d} (force per length)$
Use it when: Two long wires are a distance $d$ apart. Parallel currents attract and antiparallel currents repel.
Magnetic moment, torque, energy
$m = N I A$
$τ = m \times B, τ = N I A B sin θ$
$U = - m B cos θ$
Use it when: A coil sits in a uniform $B$ . The net force is $0$ . Stable equilibrium is when $m ∥ B$ . Shape doesn't matter, only area does.
Moving coil galvanometer
$k ϕ = N I A B$
$\frac{ϕ}{I} = \frac{N A B}{k} (current sensitivity)$
$\frac{ϕ}{V} = \frac{N A B}{k R} (voltage sensitivity)$
Use it when: Sensitivity ratios are asked. Doubling $N$ doubles current sensitivity, but voltage sensitivity is unchanged if $R$ doubles too.
Biot-Savart law
$d B = \frac{μ _{0}}{4 π} \frac{I d l sin θ}{r ^{2}}$
Use it when: You need the field from a small current element. $d B = 0$ along the line of $d l$ . Use $μ_{0} /4 π = 1 0^{- 7} T m/A$ .
Velocity selector
$v = \frac{E}{B}$
Use it when: Crossed $E$ and $B$ let a charge pass undeflected.

Trap

In τ = NIAB sinθ and U = −mB cosθ, θ is the angle between B and the normal to the coil, not the coil's plane. "Field makes 30° with the plane" means θ = 60°. Also, 1 gauss = 10⁻⁴ T.

How does NEET ask Moving Charges and Magnetism?

8 real previous-year questions from this chapter, as printed in the paper, each with its worked solution. Answer the first one here with no sign-in.

Q1PhysicsNEET UG PYQTorque on Current Loop, Magnetic Dipole

Try right here · No sign-in

A 250 – Turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85

μ A

and subjected to a magnetic field of strength 0.85 T. Work done for rotating the coil by 180º against the torque is

Answer key (C) & worked solution

Correct answer: Option C

W = M B (cos θ_{i} - cos θ_{f})

(where

θ_{i} = 0^{0}

and

θ_{f} = 18 0^{0}

) When it is rotated by angle 180

^{o}

then

W = 2 M B

W = 2 (N I A) B

= 2 \times 250 \times 85 \times 1 0^{- 6} [1.25 \times 2.1 \times 10^{- 4}] \times 85 \times 1 0^{- 2}

= 9.5 μ J

Q2PhysicsNEET UG PYQMotion in a Magnetic Field

A model for quantized motion of an electron in a uniform magnetic field B states that the flux passing through the orbit of the electron is

n (\frac{h}{e})

where n is an integer,

h

is Planck’s constant and e is the magnitude of electron’s charge. According to the model, the magnetic moment of an electron in its lowest energy state will be (m is the mass of the eletron)

\frac{h e B}{π m}

\frac{h e B}{2 π m}

\frac{h e}{π m}

\frac{h e}{2 π m}

Answer key (D) & worked solution

Correct answer: Option D

ϕ = \frac{nh}{e}

Given but

ϕ = B A

∴ \frac{ϕ}{B} = A

∴ A = \frac{ϕ}{B} = \frac{nh}{e B}

For n = 1 (lowest energy given)

A = \frac{h}{e B}

π r^{2} = \frac{h}{e B}

r^{2} = \frac{h}{π e B}

We know, magnetic moment

μ = \frac{e v r}{2}

We need velocity. Centripetal force = Magnetic force

\frac{m v ^{2}}{r} = e v B

μ = \frac{e B r}{m}

∴ μ = \frac{e v r}{2}

= \frac{e}{2} \frac{e B r}{m} r

= \frac{e ^{2} B}{2 m} r^{2} = \frac{e ^{2} B}{2 m} \frac{h}{π e B}

\frac{h e}{2 π m}

Q3PhysicsNEET UG PYQThe Moving Coil Galvanometer

Current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage applied) is 20 div/V. The resistance of the galvanometer is

A250 Ω

B25 Ω

C40 Ω

D500 Ω

Answer key (A) & worked solution

Correct answer: Option A

Current sensitivity

I_{S} = \frac{N B A}{C}

Voltage sensitivity

V_{S} = \frac{N B A}{C R _{G}}

So, resistance of galvanometer

R_{G} = \frac{I _{S}}{V _{S}} = \frac{5 \times 1}{20 \times 10 ^{- 3}} = \frac{5000}{20} = 250 Ω

Q4PhysicsNEET UG PYQAmpere's Circuital Law & Its Applications

A long straight wire of radius a carries a steady current I. The current is uniformly distributed over its cross-section. The ratio of the magnetic field B and B’, at radial distances

\frac{a}{2}

and 2a respectively, from the axis of the wire is

\frac{1}{4}

\frac{1}{2}

Answer key (C) & worked solution

Correct answer: Option C

For points inside the wire

B = \frac{μ _{0} I r}{2 π R ^{2}} (r ⩽ R)

For points outside the wire

B = \frac{μ _{0} I}{2 π R} (r ⩾ R)

According to the question

\frac{B}{B ^{'}} = \frac{\frac{μ _{0} I ( \frac{a}{2} )}{2 π a ^{2}}}{\frac{μ _{0} I}{2 π ( 2 a )}} = 1 : 1

Q5PhysicsNEET UG PYQMagnetic Field Due to Current Element

A tightly wound 100 turns coil of radius 10 cm carries a current of 7 A. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as 4ℼ x 10

^{- 7}

SI units):

A4.4 T

B4.4 mT

C44 T

D44 mT

Answer key (B) & worked solution

Correct answer: Option B

B = \frac{μ _{0} N i}{2 a}

= \frac{4 π \times 10 ^{- 7} \times 120 \times 7}{2 \times 10 \times 10 ^{- 2}}

= 140 π \times 1 0^{- 5}

= 439.6 \times 1 0^{- 5}

= 4.4 \times 1 0^{- 3} = 4.4 m T

Q6PhysicsNEET UG PYQAmpere's Circuital Law & Its Applications

A long solenoid of radius 1 mm has 100 turns per mm. If 1 A current flows in the solenoid, the magnetic field strength at the centre of the solenoid is :

A6.28 x 10

^{- 2}

B12.56 x 10

^{- 2}

C12.26 x 10

^{- 4}

D6.28 x 10

^{- 4}

Answer key (D) & worked solution

Correct answer: Option D

r = 1 mm, n = 100 turns/mm, i = 1A

B = μ_{0} ni = 4 π \times 1 0^{- 7} \times \frac{100}{10 ^{- 3}} \times 1 = 12.56 \times 1 0^{- 2} T

Q7PhysicsNEET UG PYQTorque on Current Loop, Magnetic Dipole

A 100-turn closely wound circular coil of radius 5 cm has a magnetic field of

3.14 \times 1 0^{- 3} T

at its centre. The current flowing through the coil, and the magnitude of the magnetic moment of this coil are, respectively : (Take

μ_{0} = 4 π \times 1 0^{- 7} T m / A

)

2.5 A, 2 A m^{2}

2.5 A, 20 A m^{2}

2 A, 4 A m^{2}

2 A, 10 Am^{2}

Answer key (A) & worked solution

Correct answer: Option A

Magnetic field of a circular loop:

B_{0} = \frac{μ _{0} N i}{2 R} i = \frac{2 R B _{0}}{μ _{0} N} = \frac{2 \times 5 \times 1 0 ^{- 2} \times 3.14 \times 1 0 ^{- 3}}{4 π \times 1 0 ^{- 7} \times 100} i = 2.5 A

Magnetic moment

M = N i A = 100 \times 2.5 \times 3.14 \times (5 \times 1 0^{- 2})^{2} [∵ A = π R^{2}] = 2 A m^{2}

Q8PhysicsNEET UG PYQMotion in a Magnetic Field

An electron is moving in a circular path under the influence of a transverse magnetic field of

3.57 \times 1 0^{- 2} T

. IF the value of e/m is

1.76 \times 1 0^{11} C / k g

, the frequency of revolution of the electron is

A100 MHz

B62.8 MHz

C6.28 MHz

D1 GHz

Answer key (D) & worked solution

Correct answer: Option D

f = \frac{e B}{2 π m}

f = \frac{1.76 \times 10 ^{11} \times 3.57 \times 10 ^{- 2}}{2 \times 3.14}

f = 1 0^{9} H z

1 G H z

Which topics in Moving Charges and Magnetism carry the most questions?

All 7 topics, by tagged PYQs, then practice questions. Counted from the bank. Updated 19 Oct 2026.

Topic	PYQs	Practice questions
Ampere's Circuital Law & Its Applications	9	70
Magnetic Field Due to Current Element	8	84
Magnetic Force	5	90
Motion in a Magnetic Field	5	84
Torque on Current Loop, Magnetic Dipole	5	52
The Moving Coil Galvanometer	3	38
Miscellaneous Examples	0	2

Why does Moving Charges and Magnetism show "–" until you answer 3 questions?

Unknown is not zero. Until you answer at least 3 graded questions in Moving Charges and Magnetism, ViJEEta shows – instead of a zero or a 50% default. Book exercises can raise chapter mastery up to 0.60, adaptive practice up to 0.75, and only a timed chapter test or mock can certify 0.80 and above.

How ViJEEta scores you

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Moving Charges and Magnetism: NEET PYQs and weightage

Moving Charges and Magnetism: formula sheet for NEET

Magnetic force on a charge

Radius of circular path

Time period and frequency

Pitch of helix

Force on a straight wire

Long straight wire

Centre of circular coil

Axis of circular loop

Long solenoid

Two parallel wires

Magnetic moment, torque, energy

Moving coil galvanometer

Biot-Savart law

Velocity selector

How does NEET ask Moving Charges and Magnetism?

Which topics in Moving Charges and Magnetism carry the most questions?

Why does Moving Charges and Magnetism show "–" until you answer 3 questions?

What happens when you test Moving Charges and Magnetism?

Chapters either side of Moving Charges and Magnetism by weight