Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NEET2026PhysicsChapterActual

A tightly wound circular coil has 40 turns, each of radius 10 cm . If it carries a steady current of 4 A , what is the magnitude of the magnetic field on its axis at a distance of 10 3 cm from the centre?

Options

  1. A4 10⁻⁵ T
  2. B3.2 10⁻⁴ T
  3. C8 10⁻⁵ T
  4. D10⁻⁶ T

Correct answer

A. 4 10⁻⁵ T

Step-by-step solution

The magnetic field on the axis of a circular coil is given by the formula: B = ₀ N I R^2 2(R^2 + x^2)^ 3/2 Given values are: N = 40 R = 10 cm = 0.1 m I = 4 A x = 10 3 cm = 0.1 3 m ₀ = 4 10⁻⁷ T m/A First, calculate the term (R^2 + x^2) : R^2 + x^2 = (0.1)^2 + (0.1 3 )^2 = 0.01 + 0.03 = 0.04 m ^2 Now, calculate (R^2 + x^2)^ 3/2 : (0.04)^ 3/2 = (0.2^2)^ 3/2 = (0.2)^3 = 0.008 m ^3 Substituting these values into the formula for B : B = 4 10⁻⁷ 40 4 (0.1)^2 2 0.008 B = 4 10⁻⁷ 1.6 0.016 B = 4 10⁻⁷ 100 B = 4 10⁻⁵ T Answer:

Practice Chapter on Quantrex Academy →

More from Chapter

A solid spherical body of radius R , density , and specific heat capacity s is initially at temperature T₀ . It is placed in a vacuum chamber at absolute zero and cools by emitting 2026A straight canal has motorboats departing from two terminals at opposite ends. The motorboats depart at regular intervals of T minutes in both directions and travel at a constant s 2026A wooden crate is released from rest at the top of a ramp inclined at 37^ to the horizontal. When the ramp is perfectly smooth, the crate reaches the bottom with a speed v . When t 2026A uniform horizontal beam of mass 6 kg and length L is hinged to a vertical wall at one end. The other end is supported by a light inextensible wire attached to the same wall, maki 2026A bullet P of mass 30 g moving with a speed of 200 m/s penetrates a target and comes to rest after travelling a distance of 10 cm inside it. Another bullet Q of mass 20 g moving wi 2026A small block of mass m is placed at the highest point of a smooth fixed sphere of radius R . It is given a horizontal initial speed v₁ such that it slides down the surface. The bl 2026A block of mass 2 kg is projected with an initial speed of 14 m/s on a rough horizontal surface. The coefficient of kinetic friction between the block and the surface is 0.2 . Afte 2026A uniform horizontal circular disc of mass M and radius R is rotating freely about a vertical axis passing through its center at an angular speed of 40 rpm . Two small blocks, each 2026 Full Chapter list All NEET PYQs