HC Verma: Concepts of Physics - Volume 2 Magnetic Field Due to a Current Pages 249-253: Q38 Solution: A circular loop of radius 20 cm carries a current of 10 A. An…

QPages 249-253: Q38: HC Verma: Concepts of Physics - Volume 2 Magnetic Field Due to a Current Pages 249-253: Q38 Solution: A circular loop of radius 20 cm carries a current of 10 A. An…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often mistakenly use the angle between the velocity and the loop's plane (or the radius) instead of the angle between the velocity and the magnetic field vector. Since the magnetic field at the center is directed along the axis, the angle $\theta$ in $F = qvB\sin\theta$ is the angle with the axis, not the plane.

A circular loop of radius 20 cm carries a current of 10 A. An electron crosses the plane of the loop with a speed of

2.0 \times 10^6 \text{ m s}^{-1}

. The direction of motion makes an angle of 30� with the axis of the circle and passes through its centre. Find the magnitude of the magnetic force on the electron at the instant it crosses the plane.

Step-by-Step Verified Solution

**Answer:**

F = 3.2 \times 10^{-16}

N. **Step-by-Step Explanation:**

i = 10

r = 0.2

v = 2 \times 10^6

m/s,

\theta = 30�

B = \frac{\mu_0 i}{2r} = \frac{4\pi \times 10^{-7} \times 10}{2 \times 0.2} = 3.14 \times 10^{-5}

F = evB\sin\theta = 1.6 \times 10^{-19} \times 2 \times 10^6 \times 3.14 \times 10^{-5} \times 0.5 = 5 \times 10^{-18}

QPages 249-253: Q38: HC Verma: Concepts of Physics - Volume 2 Magnetic Field Due to a Current Pages 249-253: Q38 Solution: A circular loop of radius 20 cm carries a current of 10 A. An…

Step-by-Step Verified Solution

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