Question

Directions: The following question has four choices, out of which one or more are correct. A charged particle having a positive charge q approaches a grounded metallic neutral sphere of radius R with constant speed v, as shown in the figure. Which of the following alternatives is/are correct?

• A. (A) As the charged particle draws nearer to the surface of the sphere, a current flows into the ground.
• B. (B) As the charged particle draws nearer to the surface of the sphere, a current flows out of the ground into the sphere.
• C. (C) As the particle draws nearer, the magnitude of current flowing in the connector joining the sphere shell to the ground increases.
• D. (D) As the particle draws nearer, the magnitude of current flowing in the connector joining the sphere shell to the ground decreases.

Answer 1

Answer: (A), (D)

(A) As the charged particle draws nearer to the surface of the sphere, a current flows into the ground.

Answer 2

Explanation:
The potential of the grounded sphere has to be zero, as the positive charge approaches the sphere, negative charge will be induced on the surface near to the charge ( bounded charge under the influence of the approaching positive charge so it cannot move ). The other face will be positively charged. So, negative charge must flow from earth to the sphere to neutralize the positive charge. This negative charge is acquired by the sphere from the ground, hence current flows into the ground. As the charged particle comes nearer to the sphere, the potential of the sphere due to the positive charge increases and hence more electrons per unit time will flow from the ground to the sphere and thus magnitude of current increases. Hence, it is the correct answer.