
Electric potential, also known as voltage, is a fundamental concept in electrodynamics that describes the amount of electric potential energy per unit charge at a specific point in an electric field. It is influenced by the position and magnitude of a positive test charge introduced into the field. Electric potential is measured in volts (V) and represents the energy required to move a small test charge from a reference point, typically Earth, to a specific location within the field. This electric potential energy is dependent on the position within the electric field and the intrinsic properties of objects, such as their mass or charge. Understanding electric potential helps explain the behaviour of charged objects within electric fields and is an essential aspect of electrostatics and electromagnetism.
| Characteristics | Values |
|---|---|
| Definition | The amount of work needed to move a test charge from a reference point to a specific point in a static electric field |
| Reference point | Typically, the reference point is earth or a point at infinity, although any point can be used |
| Electric potential at the reference point | Zero units |
| Test charge | Small enough that disturbance to the field is unnoticeable |
| Motion of test charge | Negligible acceleration to avoid the test charge acquiring kinetic energy or producing radiation |
| Electric potential energy | Depends only on the position in the electric field |
| Electrostatic energy | Depends on the position and the value of the test charge |
| SI derived unit | Volt (V), in honour of Alessandro Volta |
| Older units | Abvolt and statvolt |
| Pure unadjusted electric potential | Galvani potential, ϕ |
| Electric field | Cannot be expressed only as a scalar potential when time-varying fields are present |
| Electric potential and magnetic vector potential | Form a four-vector |
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What You'll Learn
- Electric potential energy depends on position in the electric field
- Electric potential is the work needed to move a charge from a reference point
- The volt is the SI unit of electric potential
- Electric potential and magnetic vector potential form a four-vector
- Electric potential energy depends on the value of the test charge

Electric potential energy depends on position in the electric field
Electric potential, also known as electric field potential or electrostatic potential, is defined as electric potential energy per unit of electric charge. It is the amount of work required to move a test charge from a reference point to a specific point in a static electric field. The reference point is usually the Earth or a point at infinity, but any point can be chosen.
Electric potential energy is a potential energy that results from conservative Coulomb forces and is associated with the configuration of a particular set of point charges within a defined system. It is measured in joules. An object may have electric potential energy due to its own electric charge or its relative position to other electrically charged objects.
The electric potential energy of a system of point charges is defined as the work required to assemble this system of charges by bringing them close together. The electrostatic potential energy, UE, of one point charge q at position r in the presence of an electric field E is defined as the negative of the work W done by the electrostatic force to bring it from the reference position to that position.
The electric potential energy of any given charge or system of charges is the total work done by an external agent in bringing them together. This work is stored as electrostatic energy, UE, which depends on the position and value of the test charge.
Therefore, electric potential energy depends on the position in the electric field.
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Electric potential is the work needed to move a charge from a reference point
Electric potential, or electric field potential, is the amount of work needed to move a unit charge from a reference point to a specific point in a static electric field. The reference point is typically Earth, but it can also be a point at infinity or any other point beyond the influence of the electric field charge. The test charge used is small enough that its disturbance to the field is unnoticeable, and its motion across the field is assumed to be without acceleration to prevent the charge from gaining kinetic energy or emitting radiation.
The electric potential at the reference point is defined as zero units. The SI unit of electric potential is the volt (V), in honour of Alessandro Volta, and the electric potential difference between two points in space is known as voltage. The volt is derived from the electric potential energy per unit charge, measured in joules per coulomb (J⋅C−1) or volt (V).
The electric potential due to a point charge is continuous in all space except at the location of the point charge itself. Similarly, an idealized line of charge has an electric potential that is continuous everywhere except on the line of charge. In electrodynamics, the electric field can be expressed as both the scalar electric potential and the magnetic vector potential, which together form a four-vector.
The electric potential energy of a charge in an electric field depends only on its position in the field. The electric force exerted by the field on a positive charge is equal to the charge multiplied by the electric field. To move a positive charge from one plate to another against an electric field, an equal and opposite force must be applied, and the work done is equal to the force multiplied by the distance.
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The volt is the SI unit of electric potential
Electric potential is the amount of work required to move a test charge from a reference point to a specific point in a static electric field. The volt, denoted by the letter V, is the SI unit of electric potential. The volt is named after Alessandro Volta, the inventor of the first battery.
The volt is defined as the electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. This can also be expressed as one joule per coulomb. In other words, one volt is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it.
The voltmeter is a device used to measure the electric potential difference between two points in space, also known as voltage. The voltmeter measures the potential difference corrected for different atomic environments. The quantity measured by a voltmeter is called the electrochemical potential or Fermi level.
The volt is used in many applications, such as automotive battery systems, household mains electricity, and high-voltage electric power transmission lines. For example, a "12 V" battery in a car has six cells connected in series, producing 12.6 volts.
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Electric potential and magnetic vector potential form a four-vector
The concept of electric potential and its role in understanding the behaviour of charged particles in electric fields is essential in electromagnetism. Electric potential, often denoted as V or φ, represents the amount of electric potential energy per unit charge when a positive test charge is introduced into an electric field. It is defined as the work done by an electric force to move a small test charge from a reference point to a specific point within the field, with the reference point typically being Earth or infinity.
In the context of electromagnetic four-potentials, the electric potential and magnetic vector potential are combined to form a four-vector. This combination allows for a concise representation of the electromagnetic field. The first component of the four-vector is the electric scalar potential, while the remaining three components constitute the magnetic vector potential. This four-vector is Lorentz covariant, meaning it remains unchanged under Lorentz transformations.
The use of four-vectors in electromagnetism offers several advantages. Firstly, it simplifies calculations by allowing the determination of electric and magnetic potentials in different inertial reference frames using standard four-vector transformation rules. Secondly, it provides a convenient framework for expressing electromagnetic waves and their equations. Additionally, the four-vector approach enables the derivation of equations of motion for charged particles in electromagnetic fields using the variational principle and Lagrange equations.
The electric and magnetic potentials are not separate entities but are interconnected. In electrodynamics, the electric field can be expressed as both the scalar electric potential and the magnetic vector potential, forming a four-vector. This relationship is particularly evident in Maxwell's equations, where the electric and magnetic fields can be described in terms of either the fields E and B or the potentials φ and A.
In summary, the electric potential and magnetic vector potential form a four-vector in the context of electromagnetic four-potentials. This combination simplifies calculations, enables the expression of electromagnetic waves, and facilitates the study of charged particle behaviour in electromagnetic fields. The four-vector nature of these potentials underscores the intrinsic relationship between electric and magnetic phenomena in the universe.
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Electric potential energy depends on the value of the test charge
Electric potential energy is a fundamental concept in physics that helps us understand the behaviour of charged particles in electric fields. It is defined as the amount of work done to move a test charge from a reference point to a specific point in a static electric field. The electric potential at the reference point, typically the Earth or infinity, is considered zero.
The electric potential field, denoted as 'V', represents the change in potential energy of the system when a test charge is introduced at a particular point in space. This change in potential energy is then divided by the value of the test charge. Interestingly, the electric potential does not depend on the value of the test charge itself but rather on the charges of the source charges and their positions.
The electric potential energy per unit charge is what we refer to as electric potential or voltage. It is measured in joules per coulomb or volts (V). This distinction is crucial because while voltage and energy are related, they are not interchangeable. For instance, a motorcycle battery and a car battery can have the same voltage but differ significantly in the amount of energy they deliver.
The electric potential is influenced by the position and value of the test charge. The test charge is chosen to be small enough that its presence does not disturb the electric field. As this charge is moved through the electric field, the work done by the electric force is stored as electrostatic energy, which depends on both the position and value of the test charge.
In summary, electric potential energy is calculated per unit charge, and the electric potential itself is independent of the test charge's value. However, the electrostatic energy associated with the test charge does depend on its value, along with its position in the electric field.
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Frequently asked questions
Electric potential is the amount of work needed to move a test charge from a reference point to a specific point in a static electric field.
Electric potential is a continuous function in all space. The electric potential at the reference point, typically earth, is zero units.
The SI unit of electric potential is the volt, denoted as V.
Electric potential energy depends only on the position in the electric field. The electric field, on the other hand, is a vector quantity that can be expressed as the gradient of the electric potential.











































