A ring of radius $R$ is uniformly charged with linear charge density $\lambda$. A unit test charge of opposite sign is released from rest at a height $h \gt 2 R$ from the centre of the ring. The test charge moves along the axis. Ignore the effect of gravity. Then

• A

  the test charge will execute simple harmonic motion about the centre of the ring.
• Correct answer
  B

  the magnitude of the force on the test charge when it moves towards the centre of the ring, increases and then decreases.
• Correct answer
  C

  the magnitude of the force on the test charge kept on the axis and near the centre of the ring decreases with increasing radius of the ring.
• D

  the speed of the test charge at the centre of the ring is proportional to $\lambda$.

Hence, the correct answer is options: 'B', 'C'.