# 26 Lecture

## Electric Potential

Electric potential is a fundamental concept in physics that helps to describe the behavior of electric charges in a system.

## Important Mcq's Midterm & Finalterm Prepration Past papers included

What is the unit of electric potential?

a) Coulomb (C)

b) Ampere (A)

c) Volt (V)

d) Tesla (T)

Which of the following is true for an equipotential surface?

a) The electric field is zero at all points on the surface

b) The electric field is perpendicular to the surface at all points

c) The electric field is parallel to the surface at all points

d) The electric field is maximum at all points on the surface

Answer: a) The electric field is zero at all points on the surface

What is the electric potential due to a point charge at a distance of 2 meters, if the charge is 4 Coulombs?

a) 2 V

b) 4 V

c) 8 V

d) 16 V

Answer: c) 8 V (V = kq/r = (9x10^9 Nm^2/C^2) x (4 C) / (2 m) = 8 V)

What is the electric potential due to a dipole at a distance of 3 meters, if the dipole moment is 5 Cm and the angle between the dipole moment and the line joining the dipole to the point is 60 degrees?

a) 1.8 V

b) 3.6 V

c) 7.2 V

d) 14.4 V

Answer: a) 1.8 V (V = k(p/r^2)cos? = (9x10^9 Nm^2/C^2) x (5x10^-6 Cm) / (3 m)^2 x cos60° = 1.8 V)

The work done in moving a charge on an equipotential surface is:

a) Zero

b) Positive

c) Negative

d) Cannot be determined

The electric potential energy of a system of two charges is -10 J. What is the work done in moving one of the charges from infinity to a distance of 2 meters from the other charge?

a) 2 J

b) 4 J

c) 8 J

d) 10 J

Answer: d) 10 J (The work done is equal to the change in potential energy, which is -10 J. Therefore, the work done is +10 J)

The electric potential due to a uniformly charged sphere at a distance outside the sphere:

a) Increases as the distance increases

b) Decreases as the distance increases

c) Remains constant as the distance increases

d) Can be zero at some distances

Answer: b) Decreases as the distance increases

What is the electric potential due to a uniform electric field of magnitude 5 N/C?

a) 2 V

b) 5 V

c) 10 V

d) 25 V

Answer: b) 5 V (V = Ed = 5 N/C x 1 m = 5 V)

Which of the following statements is true for a charged conductor in electrostatic equilibrium?

a) The electric potential is zero inside the conductor

b) The electric field is zero inside the conductor

c) The electric potential is maximum at the surface of the conductor

d) The electric field is maximum at the surface of the conductor

Answer: b) The electric field is zero inside the conductor

The electric potential due to a system of charges is the:

a) Vector sum of the electric potentials due to each charge

b) Scalar sum of the electric potentials

## Subjective Short Notes Midterm & Finalterm Prepration Past papers included

Define electric potential.

Answer: Electric potential at a point in an electric field is defined as the amount of work done in bringing a unit positive charge from infinity to that point.

What is the unit of electric potential?

Answer: The unit of electric potential is Volt (V).

What is the difference between electric potential and electric potential energy?

Answer: Electric potential is the electric potential energy per unit charge, whereas electric potential energy is the energy required to move a charge from one point to another against an electric field.

What is equipotential surface?

Answer: An equipotential surface is a surface in an electric field where all points have the same electric potential.

Why is electric potential a scalar quantity?

Answer: Electric potential is a scalar quantity because it has only magnitude and no direction.

What is the relation between electric potential and electric field?

Answer: The electric field at a point is the negative of the gradient of electric potential at that point.

What is the work done in moving a charge from a lower potential to a higher potential?

Answer: Work is done by an external agent in moving a charge from a lower potential to a higher potential.

What is the work done in moving a charge on an equipotential surface?

Answer: No work is done in moving a charge on an equipotential surface because the electric potential at all points on the surface is the same.

What is the electric potential due to a point charge?

Answer: The electric potential due to a point charge at a point in space is given by V = kq/r, where k is the Coulomb’s constant, q is the charge, and r is the distance from the point charge.

What is the electric potential due to a dipole?

Answer: The electric potential due to an electric dipole at a point in space is given by V = k(p/r^2)cos?, where k is the Coulomb’s constant, p is the dipole moment, r is the distance from the dipole, and ? is the angle between the dipole moment and the line joining the dipole to the point.

### Electric Potential

Electric potential is a fundamental concept in physics that helps to describe the behavior of electric charges in a system. It is defined as the amount of work required to move a unit positive charge from an infinitely large distance to a point in an electric field without any acceleration. Electric potential is a scalar quantity, which means that it has only magnitude and no direction. The electric potential is related to the electric field by the equation V = -?E.dr, where V is the electric potential, E is the electric field, and the integral is taken over the path from the reference point to the point of interest. The negative sign in the equation arises due to the fact that the electric field points in the direction of decreasing potential. One of the important applications of electric potential is in the study of capacitors. A capacitor consists of two conductors separated by an insulating material called a dielectric. When a potential difference is applied across the capacitor, it stores electric charge, which is proportional to the potential difference. The electric potential energy stored in a capacitor can be calculated using the equation U = ½ CV², where U is the energy stored, C is the capacitance, and V is the potential difference. The energy stored in a capacitor can be released by discharging the capacitor, which can be useful in various applications such as flash photography and defibrillation. Another important application of electric potential is in the study of electric circuits. In an electric circuit, the electric potential difference drives the flow of electric current. The electric potential difference is related to the resistance of the circuit by Ohm's law, which states that V = IR, where V is the potential difference, I is the current, and R is the resistance. Electric potential also plays an important role in the study of electric fields and forces. The electric field is the gradient of the electric potential, which means that it points in the direction of increasing potential. The electric force on a charged particle is given by F = qE, where F is the force, q is the charge of the particle, and E is the electric field. In addition to capacitors and electric circuits, electric potential has many other applications in various fields of science and engineering. For example, it is used in electrostatic painting, electrostatic precipitation, and electrostatic levitation. In conclusion, electric potential is a fundamental concept in physics that is essential for understanding the behavior of electric charges in various systems. It is related to the electric field, capacitance, electric circuits, electric fields and forces, and has numerous practical applications in various fields of science and engineering.