back to directory
NEET PHYSICSMOVING CHARGES AND MAGNETISMMedium

Question

If a square loop ABCD carrying a current i is placed near and coplanar with a long straight conductor XY carrying a current I, what will be the net force on the loop?

A

\frac{\mu_0 I i}{2\pi}

B

\frac{2\mu_0 I i L}{3\pi}

C

\frac{\mu_0 I i L}{2\pi}

D

\frac{2\mu_0 I i}{3\pi}

Step-by-Step Solution

  1. Force on Parallel Sides: The net force on the loop is the resultant of the forces acting on the sides parallel to the long straight conductor. The forces on the sides perpendicular to the conductor cancel each other out due to symmetry.
  2. Formula: The force between two parallel current-carrying conductors of length LL separated by distance dd is given by F=μ0I1I2L2πdF = \frac{\mu_0 I_1 I_2 L}{2\pi d} .
  3. Application:
  • Let the side length of the square loop be LL. Based on the standard NEET problem configuration (NEET 2016), the distance of the near side (AB) from the conductor is usually taken as L/2L/2.
  • Force on Near Side (Attractive): F1=μ0IiL2π(L/2)=μ0IiπF_1 = \frac{\mu_0 I i L}{2\pi (L/2)} = \frac{\mu_0 I i}{\pi}. This force acts towards the conductor (attractive) because currents are likely parallel (or determines direction).
  • Force on Far Side (Repulsive): The distance to the far side (CD) is L/2+L=3L/2L/2 + L = 3L/2. The force is F2=μ0IiL2π(3L/2)=μ0Ii3πF_2 = \frac{\mu_0 I i L}{2\pi (3L/2)} = \frac{\mu_0 I i}{3\pi}. This force acts away from the conductor.
  1. Net Force: Since F1>F2F_1 > F_2 and they act in opposite directions: Fnet=F1−F2=μ0Iiπ−μ0Ii3πF_{net} = F_1 - F_2 = \frac{\mu_0 I i}{\pi} - \frac{\mu_0 I i}{3\pi} Fnet=μ0Iiπ(1−13)=μ0Iiπ(23)F_{net} = \frac{\mu_0 I i}{\pi} \left( 1 - \frac{1}{3} \right) = \frac{\mu_0 I i}{\pi} \left( \frac{2}{3} \right) Fnet=2μ0Ii3πF_{net} = \frac{2\mu_0 I i}{3\pi} Note: The length LL cancels out in the final expression, making the force dependent only on the currents and constants.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from MOVING CHARGES AND MAGNETISM. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSMOVING CHARGES AND MAGNETISMsquarecarryingcurrentplacedcoplanar

More MOVING CHARGES AND MAGNETISM Questions

View all

A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron:

A.will turn towards right of direction of motion
B.will turn towards left of direction of motion
C.speed will decrease
D.speed will increase
EasySolve

A closely wound solenoid of 2000 turns and area of cross-section $1.5 \times 10^{-4} \text{ m}^2$ carries a current of $2.0 \text{ A}$. It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field $5 \times 10^{-2} \text{ T}$ making an angle of $30^{\circ}$ with the axis of the solenoid. The torque on the solenoid will be

A.$3 \times 10^{-3} \text{ N m}$
B.$1.5 \times 10^{-3} \text{ N m}$
C.$1.5 \times 10^{-2} \text{ N m}$
D.$3 \times 10^{-2} \text{ N m}$
EasySolve

A metallic rod of mass per unit length of 0.5 kg m⁻¹ is lying horizontally on a smooth inclined plane which makes an angle of 30° with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction of 0.25 T is acting on it in the vertical direction. What is the current flowing through the rod to keep it stationary?

A.7.14 A
B.5.98 A
C.14.76 A
D.11.32 A
MediumSolve

A voltmeter has a resistance of $G$ ohms and range $V$ volts. The value of resistance used in series to convert it into a voltmeter of range $nV$ volts is:

A.$nG$
B.$(n-1)G$
C.$\frac{G}{n}$
D.$\frac{G}{n-1}$
MediumSolve

The 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:

A.40 Ω
B.25 Ω
C.250 Ω
D.500 Ω
EasySolve

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

A.$6.28 \times 10^{-4} \text{ T}$
B.$6.28 \times 10^{-2} \text{ T}$
C.$12.56 \times 10^{-2} \text{ T}$
D.$12.56 \times 10^{-4} \text{ T}$
EasySolve

A square loop ABCD carrying a current $i$ is placed near and coplanar with a long straight conductor XY carrying a current $I$. The net force on the loop will be:

A.$\frac{\mu_0 I i}{2\pi}$
B.$\frac{2\mu_0 I i L}{3\pi}$
C.$\frac{\mu_0 I i L}{2\pi}$
D.$\frac{2\mu_0 I i}{3\pi}$
HardSolve

An electron moving in a circular orbit of radius $r$ makes $n$ rotations per second. The magnetic field produced at the centre has magnitude:

A.$\frac{\mu_0 n e}{2\pi r}$
B.Zero
C.$\frac{n^2 e}{r}$
D.$\frac{\mu_0 n e}{2r}$
EasySolve

Why 32,000+ students choose TopperSquare

Everything you need to crack NEET

15,000+ Chapter MCQs

Physics, Chemistry, Biology — chapter-wise, topic-wise practice

AI Performance Analytics

Know your weak topics. Get a personalised study plan.

Full NEET Mock Tests

180 questions, timed, with detailed score analysis

PYQ Sets 2010–2024

15 years of past papers with solved explanations

Start Practising Free

No credit card · 30-second signup · Free forever plan included

This neet physics practice question is part of the TopperSquare free question bank. TopperSquare offers 15,000+ chapter-wise NEET MCQs across Physics, Chemistry, and Biology with detailed step-by-step explanations, full mock tests, NEET PYQs (2010–2024), and an AI-powered performance analytics dashboard. browse all neet practice questions → · practice physics sets →

Explore more subjects:Physics MCQs•Chemistry MCQs•Biology MCQs•Botany MCQs•Zoology MCQs•NEET Mock Tests•NEET PYQs