Exams › JEE Advanced › Physics
A particle of charge 20 μC and mass 20 μg moves in a circular orbit of radius 5 cm under the influence of a uniform magnetic field B = 0.1 T. At point P on the circle, a uniform electric field is suddenly switched on, after which the particle moves along the tangent at P with constant velocity. What is the magnitude of the electric field?
- 2 V/m
- 1 V/m
- 0.5 V/m
- 5 V/m
Correct answer: 0.5 V/m
Solution
The orbital speed is v = qBr/m = 5 m/s. When the particle moves tangentially at constant speed, the net force is zero; the electric force qE must exactly cancel the centripetal magnetic force qvB, giving E = vB = 5 * 0.1 = 0.5 V/m.
Related JEE Advanced Physics questions
- Two parallel conductors lie in the plane of the paper, separated by a distance X₀. A charged particle travels with velocity v between these wires, maintaining a distance X₁ from one of them. When both wires carry identical currents I flowing in the same direction, the particle's trajectory has a curvature radius of R₁. Conversely, if the currents in the wires flow in opposite directions, the curvature radius becomes R₂. Given that X₁/X₀ equals 3, determine the ratio R₁/R₂.
- A current-carrying wire of infinite length is placed along the z-axis, carrying current I in the positive z-direction, generating a magnetic field B. What is the value of the line integral ∮ B⋅dℓ along a straight path connecting the points (−√3a, a, 0) and (a, a, 0)? [Here, μ₀ represents the permeability of free space.]
- A charged particle has specific charge (charge-to-mass ratio) alpha. It starts from rest at the origin at t = 0 with initial velocity v0*i_hat + v0*j_hat in a uniform magnetic field B0*i_hat. Find the coordinates of the particle at time t = pi / (alpha * B0).
- Two infinitely long, thin, straight parallel wires are separated by a distance of 0.1 m and each carries a current of 10 A. A point P is equidistant from both wires at a distance of 0.1 m from each. Find the magnitude of the net magnetic field at P when the currents flow in (i) the same direction and (ii) opposite directions.
- A straight conducting wire of length 2*pi*R carries a steady current I. It is bent so that it forms an arc of a circle of radius R, leaving a gap of angle theta (in radians) at the top. Find the magnitude of the magnetic field at the centre O of the circle. (Assume the two short straight ends at the gap meet at the centre and contribute zero field.)
- An electric dipole moves with velocity v in a region of uniform magnetic field B directed into the plane of the page. Case I: The dipole moment P is horizontal, parallel to v, both directed to the right. Case II: The dipole moment P is vertical (upward) and v is horizontal (to the right). Which statement is correct regarding the effect of the external magnetic field on the dipole?
⚔️ Practice JEE Advanced Physics free + battle 1v1 →