Equipotential surfaces and the field-potential relation — NEET & JEE Questions

Question 1 · difficulty L1 · recall

An equipotential surface is a surface on which

• A. electric potential has the same value at every point
• B. electric field is zero at every point
• C. charge density is always zero
• D. all charges must be at rest

Question 2 · difficulty L2 · understanding

How is the electric field oriented relative to an equipotential surface?

• A. Tangential to it
• B. Perpendicular to it
• C. At 45 degrees to it
• D. Randomly oriented

Question 3 · difficulty L2 · understanding

How much work is done by the electrostatic field in moving a charge along an equipotential surface?

• A. Positive work
• B. Negative work
• C. Zero work
• D. Infinite work

Question 4 · difficulty L2 · understanding

In a region where equipotential surfaces are very closely spaced, the electric field is generally

• A. weak
• B. strong
• C. zero
• D. necessarily uniform and zero

Question 5 · difficulty L3 · application

The electric potential decreases uniformly by 20 V over a distance of 0.50 m in the +x direction. What is the x-component of the electric field?

• A. +10 V/m
• B. -10 V/m
• C. +40 V/m
• D. -40 V/m

Question 6 · difficulty L3 · application

Two points A and B lie on the same equipotential surface. A charge of $3\,\mu\text{C}$ moves from A to B. What is the change in its potential energy?

• A. $3\,\mu\text{J}$
• B. $-3\,\mu\text{J}$
• C. Zero
• D. Cannot be determined without distance

Question 7 · difficulty L3 · application

The potential at x = 0 m is 100 V and at x = 2 m is 40 V, with potential varying linearly between them. What is the electric field in this region?

• A. +30 V/m
• B. -30 V/m
• C. +70 V/m
• D. -70 V/m

Question 8 · difficulty L3 · application

For an isolated positive point charge, the equipotential surfaces are

• A. concentric spheres centred on the charge
• B. parallel planes
• C. cylinders with arbitrary axes
• D. straight lines passing through the charge

Question 9 · difficulty L4 · application

A uniform electric field points in the +x direction. Which statement about potential is correct?

• A. Potential increases with x
• B. Potential decreases with x
• C. Potential is independent of x
• D. Potential must be zero everywhere

Question 10 · difficulty L4 · application

Two neighbouring equipotential surfaces differ in potential by 50 V. In region P they are 5 cm apart, while in region Q they are 1 cm apart. Approximately how do the electric-field magnitudes compare?

• A. $E_P=E_Q$
• B. $E_Q=5E_P$
• C. $E_P=5E_Q$
• D. $E_Q=25E_P$