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Question
Equipotentials at a great distance from a collection of charges whose total sum is not zero are approximately.
Options
spheres
planes
paraboloids
ellipsoids
Solution
spheres
Explanation:
The collection of charges, whose total sum is not zero, with regard to great distance can be considered as a single-point charge. The equipotential surfaces due to a point charge are spherical.
Important point:
- The electric potential due to point charge q is given by V = q/4πε0r
- It means electric potential due to point charge is same for all equidistant points. The locus of these equidistant points, which are at the same potential, form spherical surface.
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RELATED QUESTIONS
A regular hexagon of side 10 cm has a charge 5 µC at each of its vertices. Calculate the potential at the centre of the hexagon.
Two charges 2 μC and −2 µC are placed at points A and B 6 cm apart.
- Identify an equipotential surface of the system.
- What is the direction of the electric field at every point on this surface?
Describe schematically the equipotential surfaces corresponding to
(a) a constant electric field in the z-direction,
(b) a field that uniformly increases in magnitude but remains in a constant (say, z) direction,
(c) a single positive charge at the origin, and
(d) a uniform grid consisting of long equally spaced parallel charged wires in a plane.
The top of the atmosphere is at about 400 kV with respect to the surface of the earth, corresponding to an electric field that decreases with altitude. Near the surface of the earth, the field is about 100 Vm−1. Why then do we not get an electric shock as we step out of our house into the open? (Assume the house to be a steel cage so there is no field inside!)
The discharging current in the atmosphere due to the small conductivity of air is known to be 1800 A on an average over the globe. Why then does the atmosphere not discharge itself completely in due course and become electrically neutral? In other words, what keeps the atmosphere charged?
Answer the following question.
Write two important characteristics of equipotential surfaces.
Equipotential surfaces ______.
The work done to move a charge along an equipotential from A to B ______.
- cannot be defined as `- int_A^B E.dl`
- must be defined as `- int_A^B E.dl`
- is zero.
- can have a non-zero value.
What is meant by an equipotential surface?
