A charge \(q\) is placed in a uniform electric field \(E.\) If it is released, then the kinetic energy of the charge after travelling distance \(y\) will be:
1. \(qEy\)
2. \(2qEy\)
3. $\frac{qEy}{2}$
4. $\sqrt{qEy}$

In Millikan oil drop experiment, a charged drop falls with a terminal velocity v. If an electric field E is applied vertically upwards it moves with terminal velocity 2v in upward direction. If electric field reduces to E/2 then its terminal velocity will be:
1. v/2
2. v
3. 3v/2
4. 2v

The electric field at centre \(O\) of a semicircle of radius \(a\) having linear charge density \(\lambda\) is given by:

     
1. \(\frac{2\lambda}{\epsilon_0 a}\)
2. \(\frac{\lambda\pi}{\epsilon_0 a}\)
3. \(\frac{\lambda}{2\pi \epsilon_0 a}\)
4. \(\frac{\lambda}{\pi \epsilon_0 a}\)