
Electric potential, also known as electric field potential or potential drop, is a fundamental concept in physics that deals with the amount of work or energy required to move a unit of electric charge from one point to another within an electric field. This potential is influenced by the presence of charged objects, with the direction of the force depending on the charge. If the object carries a positive charge, the force aligns with the electric field vector, whereas a negative charge results in a force in the opposite direction. The electric potential energy per unit charge, or simply electric potential, can be calculated using the formula: electric potential = electric potential energy / charge. This calculation can be performed for both static and dynamic electric fields, with the unit expressed in joules per coulomb (J⋅C−1) or volts (V). Understanding electric potential is crucial for comprehending the behaviour of charged particles and the underlying principles of electrostatics and electrodynamics.
| Characteristics | Values |
|---|---|
| Definition | The amount of work/energy needed per unit of electric charge to move the charge from a reference point to a specific point in an electric field |
| Formula | Ue = qtvp = qtk∑1^N qi/ri |
| Electric Potential at Infinity | Zero |
| Electric Potential at Ground | Zero |
| Electric Potential at Reference Point | Zero |
| Electric Potential and Electric Field Relationship | Electric potential is a scalar, while electric field is a vector |
| Direction of Electric Potential | Electric potential has no direction |
| Electric Potential in Dynamic Fields | The electric potential and magnetic vector potential form a four-vector |
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What You'll Learn

Electric potential energy per unit charge
Electric potential, also known as electric field potential, is defined as the amount of work or energy needed per unit of electric charge to move a charge from a reference point to a specific point in an electric field. In other words, it is the energy per unit charge, or the electric potential energy per unit charge. This value can be calculated in either a static (time-invariant) or a dynamic (time-varying) electric field at a specific time, with the unit joules per coulomb (J⋅C−1) or volt (V).
The concept of electric potential is closely linked with potential energy. A test charge, q, has an electric potential energy, UE, given by the work required to assemble the system of charges by bringing them close together from an infinite distance. The potential energy and, hence, the electric potential are defined up to an additive constant. One must arbitrarily choose a position where the potential energy and the electric potential are zero. The electric potential at the reference point is assumed to be zero units, and this reference point is typically earth or a point at infinity.
The change in electrostatic potential energy, UE, of a point charge q that has moved from the reference position rref to position r in the presence of an electric field E is the negative of the work done by the electrostatic force to bring it from the reference position to that position. When the curl ∇ × E is zero, the line integral does not depend on the specific path chosen but only on its endpoints. This occurs in time-invariant electric fields, where the electric field is conservative and Coulomb's law can be used.
In electric circuits, if the total electric force at a point pulls leftwards, the potential energy is lower when the charge moves leftwards. This means that the potential energy is a way to indicate how much force pulls and which way stuff will move if allowed. Voltage, or potential difference, is the name given to this difference in potential energy per unit charge between two points.
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Electric potential and electric field
Electric potential, also known as electric field potential or electrostatic potential, is defined as the amount of work or energy required per unit of electric charge to move a charge from a reference point to a specific point in an electric field. In other words, it is the electric potential energy per unit charge. This value can be calculated in either a static (time-invariant) or dynamic (time-varying) electric field, with the unit joules per coulomb (J⋅C−1) or volt (V).
The concept of electric potential is closely linked to potential energy. The potential energy of a test charge is given by the equation:
> $U_p = q_tV_p = q_tk\sum_1^N \frac{q_i}{r_i}$
Where $U_p$ is the electric potential energy, $q_t$ is the test charge, and $V_p$ is the electric potential. The electric potential at the reference point, typically Earth or a point at infinity, is defined as zero units.
The direction of the electric field force on a charged object depends on the charge of the object. If the object has a positive charge, the force will be in the direction of the electric field vector at the location of the charge. If the object has a negative charge, the force will be in the opposite direction. The magnitude of the force is given by the quantity of the charge multiplied by the magnitude of the electric field vector.
It is important to note that the electric potential is a scalar quantity, while the electric field is a vector quantity. This means that the electric potential has no direction, whereas the electric field has both magnitude and direction. Evaluating the electric potential is generally simpler than evaluating the electric field due to this difference in nature.
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Positive and negative charge directions
Electric potential is closely linked with potential energy and is defined as the amount of work or energy needed per unit of electric charge to move the charge from a reference point to a specific point in an electric field.
Now, electric charge can be positive or negative. The most common charge carriers are the positively charged proton and the negatively charged electron. If there are more electrons than protons in a piece of matter, it will have a negative charge, and if there are fewer, it will have a positive charge. The movement of any of these charged particles constitutes an electric current.
In an isolated system, the total charge remains the same—the amount of positive charge minus the amount of negative charge does not change over time. Like charges repel each other and unlike charges attract each other. If a charge is pushed in the same direction as the electric field, it is called a positive charge, and if it is pushed in the opposite direction, it is called a negative charge.
In electrostatics, the Maxwell-Faraday equation reveals that if the object has a positive charge, the force will be in the direction of the electric field vector at the location of the charge; if the charge is negative, the force will be in the opposite direction.
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Ground potential
In electricity, the term "ground" is used to refer to a connection to the Earth, which has a constant potential that can be used as a reference point for measuring other potentials. This is important for safety, as grounding limits the build-up of static electricity and protects against electric shock. In electrical power distribution systems, an earthing or grounding system defines the electrical potential of the conductors relative to the Earth's conductive surface.
Ground loops or earth loops are a common issue in electrical systems. They occur when two points of a circuit are intended to have the same ground reference potential but instead have different potentials between them. This can be caused by electromagnetic induction or current leaking from the hot side of the power line into the ground system. The induced currents can be large due to the low resistance of the loop, often less than 1 ohm. Ground loops can cause noise, hum, and interference in audio, video, and computer systems.
To prevent ground loops, wiring practices should ensure that all vulnerable signal circuits are referenced to a single point as the ground. Differential signaling can also be used to reject ground-induced interference. In some cases, battery-powering circuits can avoid ground loops by disconnecting the device from mains power. However, it is important to note that removing ground connections to equipment may eliminate the safety protection provided by the ground connection.
In circuit design, grounding considerations are crucial. Large currents may flow through the ground plane, leading to voltage differences in the ground reference across the circuit. Phase lock loop circuits are particularly vulnerable to disturbances, which can cause frequency jitter and loss of lock. To mitigate these issues, separate ground planes for analog and digital parts of the circuit may be used, tied together at a carefully chosen star point.
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Calculating electric potential
Electric potential, also known as electric field potential or potential drop, is defined as the amount of work or energy required per unit of electric charge to move the charge from a reference point to a specific point in an electric field. It is calculated in joules per coulomb (J⋅C−1) or volts (V).
The electric potential at a reference point, typically the earth or a point at infinity, is defined as zero units. The electric potential at any other point is the sum of the individual electric potentials created by each charge. This can be calculated using the equation:
V = V1 + V2 + ... + VN = ∑1^N Vi
Where:
- V is the net electric potential at point P
- V1, V2, ..., VN are the electric potentials at point P produced by the charges q1, q2, ..., qN
The electric potential of a point charge can be calculated using the equation:
V = k * q / r
Where:
- V is the electric potential
- K is a constant equal to 8.99 x 10^9 N ⋅ m^2/C^2
- Q is the test charge
- R is the distance from the point charge to the test charge
The electric potential outside a charged conducting cylinder can be found using equations that take into account the radius and charge per unit length of the cylinder. For a ring of charge, the potential is given by the radius and total charge.
In some cases, calculating electric potential directly may not be feasible. In such situations, one can go back to the definition of potential in terms of the electric field to find a solution.
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Frequently asked questions
Electric potential, also known as electric field potential or electrostatic potential, is the amount of energy per unit of electric charge needed to move a charge from a reference point to a specific point in an electric field.
Electric potential is a scalar and has no direction. However, the electric field is a vector and has direction. The direction of the electric field vector at the location of a charge determines the direction of the force acting on it. If the charge is positive, the force will be in the direction of the electric field vector. If the charge is negative, the force will be in the opposite direction.
The formula for electric potential (V) due to a point charge (Q) at a distance (r) from the location of the charge is:
V = (1 / 4πε0) * (Q / r)
Where:
- V is the electric potential
- Q is the point charge
- r is the distance from the location of the charge
- ε0 is the permittivity of a vacuum
Electric potential is closely linked to potential energy. The electric potential energy of a test charge (q) is given by the formula:
U_p = q_t * V_p = q_t * k * sum(q_i / r_i)
Where:
- U_p is the electric potential energy
- q_t is the test charge
- V_p is the electric potential
- k is a constant
- q_i are the source charges
- r_i are the distances from the source charges to the test charge































