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. - Physics

Short Note

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!)



We do not get an electric shock as we step out of our house because the original equipotential surfaces of open-air change, keeping our body and the ground at the same potential.

Concept: Equipotential Surfaces
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Chapter 2: Electrostatic Potential and Capacitance - Exercise [Page 91]


NCERT Physics Class 12
Chapter 2 Electrostatic Potential and Capacitance
Exercise | Q 2.36 (a) | Page 91
NCERT Physics Class 12
Chapter 2 Electrostatic Potential and Capacitance
Exercise | Q 37.1 | Page 92


Define an equipotential 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.

What are the forms of energy into which the electrical energy of the atmosphere is dissipated during a lightning?
(Hint: The earth has an electric field of about 100 Vm−1 at its surface in the downward direction, corresponding to a surface charge density = −10−9 C m−2. Due to the slight conductivity of the atmosphere up to about 50 km (beyond which it is good conductor), about + 1800 C is pumped every second into the earth as a whole. The earth, however, does not get discharged since thunderstorms and lightning occurring continually all over the globe pump an equal amount of negative charge on the earth.)

Draw equipotential surfaces:

(1) in the case of a single point charge and

(2) in a constant electric field in Z-direction. Why are the equipotential surfaces about a single charge not equidistant?

(3) Can electric field exist tangential to an equipotential surface? Give reason

Draw the equipotential surfaces due to an electric dipole. Locate the points where the potential due to the dipole is zero.

Depict the equipotential surfaces for a system of two identical positive point charges placed a distance(d) apart?

Define equipotential surface. 

Depict the equipotential surface due to
(i) an electric dipole,
(ii) two identical positive charges separated by a distance.

Find the amount of work done in rotating an electric dipole of dipole moment 3.2 x 10- 8Cm from its position of stable equilibrium to the position of unstable equilibrium in a uniform electric field if intensity 104 N/C.  

Statement - 1: For practical purpose, the earth is used as a reference at zero potential in electrical circuits.

Statement - 2: The electrical potential of a sphere of radius R with charge Q uniformly distributed on the surface is given by `Q/(4piepsilon_0R)`.

A particle of mass 'm' having charge 'q' is held at rest in uniform electric field of intensity 'E'. When it is released, the kinetic energy attained by it after covering a distance 'y' will be ______.

S1 and S2 are the two imaginary surfaces enclosing the charges +q and -q as shown. The electric flux through S1 and S2 are respectively ______.

Equipotentials at a great distance from a collection of charges whose total sum is not zero are approximately.

A unit charge moves on an equipotential surface from a point A to point B, then ______.

Which of the following is NOT the property of equipotential surface?

Can two equipotential surfaces intersect each other? 

Equipotential surfaces are shown in figure. Then the electric field strength will be ______.

What is meant by an equipotential surface?


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