Five balls marked \(a\) to \(e\) are suspended using separate threads. Pairs \((b,c)\) and \((d,e)\) show electrostatic repulsion while pairs \((a,b), (c,e)\) and \((a,e)\) show electrostatic attraction. The ball marked \(a\) must be:
1. negatively charged.
2. positively charged.
3. uncharged.
4. Any of the above is possible

When a plastic rod rubbed with wool is brought near the knob of a negatively charged gold-leaf electroscope, the gold leaves:

1. Contract

2. Dilate

3. Start oscillating

4. Collapse completely

Which of the following is not true about the electric charge?

1. Charge on a body is always an integral multiple of a certain charge known as the charge of an electron.

2. Charge is a scalar quantity.

3. Net charge on an isolated system is always conserved.

4. Charge can be converted into energy and energy can be converted into charge.

Which of the following processes involves the principle of electrostatic induction?

1. Pollination

2. Chocolate making

3. Xerox copying

4. All of these

When a conducting soap bubble is negatively charged then:

1. Its size starts varying arbitrarily

2. It expands

3. It contracts

4. No change in its size takes place

Coulomb's law is analogous to:

1. Charge conservation law

2. Newton's second law of motion

3. Law of conservation of energy

4. Newton's law of gravitation

Two-point charges Q₁ and Q₂ exert a force F on each other when kept at a certain distance apart. If the charge on each particle is halved and the distance between the two particles is doubled, then the new force between the two particles would be:

1. $\frac{\mathrm{F}}{2}$

2. $\frac{\mathrm{F}}{4}$

3. $\frac{\mathrm{F}}{8}$

4. $\frac{\mathrm{F}}{16}$

Two equally charged identical small balls kept at some fixed distance apart exert a repulsive force F on each other. A similar uncharged ball, after touching one of them is placed at the mid-point of the line joining the two balls. The force experienced by the third ball is: 

1. 4F

2. 2F

3. F

4. $\frac{\mathrm{F}}{16}$

Two equal point charges A and B are R distance apart. A third point charge placed on the perpendicular bisector at a distance d from the centre will experience a maximum electrostatic force when:

1. $\mathrm{d}=\frac{\mathrm{R}}{2\sqrt{2}}$

2. $\mathrm{d}=\frac{\mathrm{R}}{\sqrt{2}}$

3. $\mathrm{d}=\mathrm{R}\sqrt{2}$

4. $\mathrm{R}=2\sqrt{2}\mathrm{R}$

A charged gold leaf electroscope has its leaves apart by a certain amount of having enclosed air. When the electroscope is subjected to X-rays, then the leaves:

1. Further dilate

2. Start oscillating

3. Collapse

4. Remain unaltered