Electrostatic Potential and Capacitance Physics - Electrostatic Potential and Capacitance

Two large conducting spheres carrying charges Q₁ and Q₂ are brought close to each other. Is the magnitude of electrostatic force between them exactly given by $\frac{\text{Q}_1\text{Q}_2}{{4}\pi\in_{0}\text{r}^{2}}$, where r is the distance between their centres?

1. A parallel plate capacitor is charged and then isolated. The effect of increasing the plate separation on charge, potential and capacitance respectively are:

1. Increases, decreases, decreases.
2. Constant, increases, decreases.
3. Constant, decreases, decreases.
4. Constant, decreases, increases.

2. In a parallel plate capacitor, the capacity increases if:

1. Area of the plate is decreases.
2. Distance between the plates increases.
3. Area of the plate is increases.
4. Dielectric constant decreases.

3. A parallel plate capacitor has two square plates with equal and opposite charges. The surface charge densities on the plates are $+\sigma$ and $-\sigma$ respectively. In the region between the plates the magnitude of the electric field is:

1. $\frac{\sigma}{2\in_0}$

2. $\frac{\sigma}{\in_0}$

3. 0
4. None of these.

4. If a parallel plate air capacitor consists of two circular plates of diameter 8cm. At what distance should the plates be held so as to have the same capacitance as that of sphere of diameter 20cm?

1. 9mm
2. 4mm
3. 8mm
4. 2mm

5. If a charge of + 2.0 × 10^-8C is placed on the positive plate and a charge of - 1.0 × 10^-8C on the negative plate of a parallel plate capacitor of capacitance $1.2\times10^{-3}\mu\text{F},$ then the potential difference developed between the plates is:

1. 6.25V
2. 3.0V
3. 12.5V
4. 25V

1. If an isolated sphere has a capacitance 50pE Then radius is:

1. 90cm
2. 45cm
3. 45m
4. 90m

2. How much charge should be placed on a capacitance of 25 pF to raise its potential to 105V?

1. $1\mu\text{C}$
2. $1.5\mu\text{C}$
3. $2\mu\text{C}$
4. $2.5\mu\text{C}$

3. Dimensions of capacitance is:

1. [M L^-2 T⁴ A²]
2. [M^-1 L^-1 T³ A¹]
3. [M^- L^-2 T⁴ A²]
4. [M⁰ L^-2 T⁴ A¹]

4. Metallic sphere of radius R is charged to potential V. Then charge q is proportional to:

1. V
2. R
3. Both V and R
4. None of these

5. If 64 identical spheres of charge q and capacitance C each are combined to form a large sphere. The charge and capacitance of the large sphere is:

1. 64q, C
2. 16q, 4C
3. 64q, 4C
4. 16q, 64C

1. At which of the points 1, 2, and 3 is the electric field is zero?

1. 1
2. 2
3. 3
4. Both (a) and (b)

2. The signs of charges Q₁ and Q₂ respectively are:

1. Positive and negative.
2. Negative and positive.
3. Positive and positive.
4. Negative and negative.

3. Which of the two charges Q₁ and Q₂ is greater in magnitude?

1. Q₂
2. Q₁
3. Same.
4. Can't determined.

4. Which of the following statement is not true?

1. Electrostatic force is a conservative force.
2. Potential energy of charge q at a point is the work done per unit charge in bringing a charge from any point to infinity.
3. When two like charges lie infinite distance apart, their potential energy is zero.
4. Both (a) and (c).

5. Positive and negative point charges of equal magnitude are kept at $\Big(0,0,\frac{\text{a}}{2}\Big)$ and $\Big(0,0,\frac{\text{-a}}{2}\Big)$ respectively.

The work done by the electric field when another positive point charge is moved from (-a, 0, 0) to (0, a, 0) is to:

1. Positive.
2. Negative.
3. Zero.
4. Depends on the path connecting the initial and final positions.

1. Which among the following is an example of polar molecule?

1. O₂
2. H₂
3. N₂
4. HCI

2. When air is replaced by a dielectric medium of constant K, the maximum force of attraction between two charges separated by a distance:

1. Increases K times.
2. Remains unchanged.
3. Decreases K times.
4. Increases 2K times.

3. Which of the following is a dielectric?

1. Copper.
2. Glass.
3. Antimony (Sb).
4. None of these.

4. For a polar molecule, which of the following statements is true?

1. The centre of gravity of electrons and protons coincide.
2. The centre of gravity of electrons and protons do not coincide.
3. The charge distribution is always symmetrical.
4. The dipole moment is always zero.

5. When a comb rubbed with dry hair attracts pieces of paper. This is because the?

1. Comb polarizes the piece of paper.
2. Comb induces a net dipole moment opposite to the direction of field.
3. Electric field due to the comb is uniform.
4. Comb induces a net dipole moment perpendicular to the direction of field.