Question

A charged particle enters a magnetic field H with its initial velocity making an angle of ${45}^o$ with H. Then the path of the particle will be

• A. Circle
• B. Helical
• C. A straight line
• D. A circle

Answer 1

Answer: (B)

Helical

At point A, charge is entering in a magnetic field in which direction of field is shown in the figure. The velocity of particle is u making an angle of ${45}^o$ with field. We resolve it in two directions, one along the field and other perpendicular to it. Since u $\sin {45}^o$ is perpendicular to H, it will create a rotatory effect on the charge. So charge particle will start rotating with axis along the direction of H. At the same time it will move forward with velocity u $\cos {45}^o$. Under both these motions, it will have helical path as shown in the figure.