All Exams Test series for 1 year @ ₹349 only
Question

Consider a long current carrying solenoid. If Rahul plots the magnetic field lines inside this long current carrying solenoid, then it appears:

This question was previously asked in
RRB NTPC 2024 Undergraduate CBT 1 Question Paper (29-Aug-2025) (Shift 1)
The correct answer is

uniform at all points

In a long current-carrying solenoid, the magnetic field inside is characterized by uniformity. This means that the magnetic field lines are parallel and equally spaced throughout the interior of the solenoid. The reason for this uniformity is the symmetrical and homogeneous winding of the coils and the substantial length of the solenoid.

To understand this, consider the following:

  1. Structure of a Solenoid: A solenoid is a coil of wire designed to produce a magnetic field when an electric current passes through it. When the solenoid is long, it approximates the behavior of an ideal magnetic field generator.
  2. Magnetic Field Inside: The magnetic field (\(B\)) inside a long solenoid is given by the formula:
    B = μ₀nI
    where μ₀ is the permeability of free space, n is the number of turns per unit length, and I is the current. This equation shows that the field strength is uniform as it depends only on constant factors for a given solenoid setup.
  3. Behavior at Ends: While the magnetic field is approximately uniform along the length of a long solenoid, it weakens near the ends. However, the configuration here is between 'long' solenoids, wherein we consider the mid-region.

Hence, when Rahul plots the magnetic field lines, they appear uniform at all points inside this long solenoid, with no significant variation in density or direction away from the ends.

Was this answer helpful?

Similar Questions

  1. The region surrounding a magnet in which its influence can be felt is called its:

Important Questions from Magnetic Field

  1. Three infinitely long wires, each carrying equal current are placed in the xy-plane along x = 0, +d and −d. On the xy-plane, the magnetic field vanishes at

  2. Choose the incorrect statement from the following regarding magnetic lines of field -

  3. A wire of length L is bent in the form a circular loop. And current is passed through the loop. The magnetic field induction at the centre of the loop is B. Find the current passing through the loop.

  4. The magnetic field at the centre of a circular coil of radius r and carrying I is B. What is the magnetic field at a distance \(x = \sqrt{3}r\) from the centre, on the axis of the coil?

  5. Two identical coils carry equal currents and have a common center, but their planes are at right angles to each other. What is the magnitude of the resultant magnetic field at the center, if field due to one coil alone is B?

Need Expert Advice?
Upcoming Exams
RRB NTPC
September 27, 2026
RRB Technician
October 06, 2026
Test Series
RRB ALP img
Railways
RRB ALP 2026 Mock Test series
1035 Tests 1 Tests Free
1002 Attempts
4.3(238)
English, Hindi

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App