Test: Potential due to a Point Charge & Electric Dipole (November 17) - NEET MCQ

Force on a unit point charge kept at a distance r from the charge = q/r². 

Therefore, work done to bring that point charge through a small distance dr = q/r² * (-dr). Therefore, the potential of that point is = .

Work done = potential*charge by definition. We know that the potential of a point is the amount of work done to bring a unit charge from infinity to a certain point. Therefore, work done W=q*V=4*10^-3*200J=0.8J. The work done is positive in this case.

Electric potential between +q and +q isand electric potential between two charges +q and –q is  . Therefore the electric potential of the system is Electric potential is a scalar quantity and thus the system becomes zero-potential-system.

Increase in potential energy of the electron when it strikes another plate = Potential difference*charge of electron=20*1.6*10^-19 J=3.201*10^-18J and as the electron was at rest initially, this energy will be converted to kinetic energy completely. Therefore, 0.5*mass of electron*(velocity)²=3.201*10^-18J. Substituting m=9.11*10^-31kg, we get v=2.65*10⁶ m/s.

Definition based

q=6x10^-10 c
Q=-2x10^-9c
r₁=3x10^-2m
r₂=4x10^-2m
△v_Q=w/q
(1/4πε_o)-2x10^-9/10^-2[(1/4)-(1/3)]=W/6x10^-3
9x10⁹x2x10^-9x6x10^-3/12x10^-2=W
W=9x10^-3x10²
W=0.9J

Potential difference between two points is given by

V_a - V_b = W/q₀

Work, W = 2 J

Charge, q₀ = 20 C

Potential difference = 2/20 = 0.1 V

The correct option is C.

Since Potential difference between two points in equipotential surfaces is zero, the work done between two points in equipotential surface is also zero.

E.l = V   where,
E = electric field intensity = 12 N/C
V = electric potential = 6 J/C
=> distance between A and B, 
l = (6 / 12) m or (1 / 2) m = 0.5 m
 

The overall work performed in carrying a 2coulomb charge in a circular orbit of radius 3 m around a charge of 10 coulomb is calculated below.
It is a well-known fact that W=qdv.
Here dV is the change in overall potential. In the circular orbit of r potential at each point is similar.
Most significantly, the value of r is 3.  
The value of dv=0 and hence W=q₀=0.