Three charges \(4q,Q,\) and \(q\) are in a straight line in the position of \(0,l/2,\) and \(l\) respectively. The resultant force on \(q\) will be zero if \(Q\) equal to:
1. \(-q\)
2. \(-2q\)
3. \(\frac{-q}{2}\)
4. \(4q\)

Two small spheres each having the charge \(+Q\) are suspended by insulating threads of length \(L\) from a hook. If this arrangement is taken in space where there is no gravitational effect, then the angle between the two suspensions and the tension in each will be:

1. \(180^\circ,\) \(\frac{1}{4 \pi \epsilon_{0}} \frac{Q^{2}}{(2 L )^{2}}\)

2. \(90^\circ,\) \(\frac{1}{4 \pi \epsilon_{0}} \frac{Q^{2}}{(L )^{2}}\)

3. \(180^\circ,\) \(\frac{1}{4 \pi \epsilon_{0}} \frac{Q^{2}}{2 L ^{2}}\)

4. \(180^\circ,\) \(\frac{1}{4 \pi \epsilon_{0}} \frac{Q^{2}}{ L ^{2}}\) 

Two charges each of 1 coulomb are at a distance 1 km apart, the force between them is 

(1) 9 × 10³ Newton

(2) 9 × 10^–3 Newton

(3) 1.1 × 10^–4 Newton

(4) 10⁴ Newton

Two charges \(+2\) C and \(+6\) C are repelling each other with a force of \(12\) N. If each charge is given \(-2\) C of charge, then the value of the force will be:

The dielectric constant of pure water is 81. Its permittivity will be:

1. 7.12 × 10^–10 MKS units

2. 8.86 × 10^–12 MKS units

3. 1.02 × 10¹³ MKS units

4. Cannot be calculated

Force of attraction between two point charges Q and – Q separated by d meter is F_e. When these charges are given to two identical spheres of radius R = 0.3 d whose centres are d meter apart, the force of attraction between them is 

1. Greater than F_e

2. Equal to F_e

3. Less than F_e

4. None of the above

One metallic sphere A is given a positive charge whereas another identical metallic sphere B of the exact same mass as of A is given an equal amount of negative charge. Then:

(1) mass of A and mass of B are the same.

(2) mass of A is more.

(3) mass of B is less.

(4) mass of B is more.

Two charges each equal to 2μC are 0.5m apart. If both of them exist inside the vacuum, then the force between them is 

(1) 1.89 N

(2) 2.44 N

(3) 0.144 N

(4) 3.144 N