Electrostatic Potential and Capacitance Test

Result

Electrostatic Potential and Capacitance Test - 3

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Question 1
4 / -1

Figure shows the field lines of a positive point charge. The work done by the field in moving a small positive charge from Q to P is

A
zero

B
positive

C
negative

D
data insufficient

Solution

In moving a small positive charge from Q to P, work has to be done by an external agency against the electric field. Therefore, work done by the field is negative.
Question 2
4 / -1

Figure shows the field lines of a point negative charge. In going from B to A, the kinetic energy of a small negative charge will

A
increase

B
decrease

C
remain constant

D
data insufficient

Solution

Due to force of repulsion on the negative charge, velocity decreases and hence the kinetic energy decreases in going from B to A.
Question 3
4 / -1

Two tiny spheres carrying charges 1.8 μC and 2.8μC are located at 40 cm apart. The potential at the mid-point of the line joining the two charges is

A
3.8 × 10⁴ V

B
2.1 × 10⁵ V

C
4.3 × 10⁴ V

D
3.6 × 10⁵ V

Solution

Here q₁ = 1.8 μC = 1.8 × 10⁻⁶ C, q₂ = 2.8 μC = 2.8 × 10⁻⁶C

Distance between the two spheres = 40 cm = 0.4 m
For the mid-point r₁ = r₂ = 0.40/2 = 0.2 m Potential at O,
Question 4
4 / -1

In the question number 18, the potential at a point 20cm from the mid-point of the line joining the two charges in a plane normal to the line and passing through the mid-point is

A
1.4 × 10⁵ V

B
4.2 × 10³ V

C
2.9 × 10⁴ V

D
3.7 × 10⁵ V

Solution

From the figure, potential at P,
Question 5
4 / -1

Four equal charges q each are placed at four corners of a square of side a each. Work done in carrying a charge −q from its centre to infinity is

A
zero

B

C

D

Solution

Potential at centre O of the square

Work done in shifiting (−Q) charge from centre to infinity