Electric Potential Calculator

Calculate the electric potential energy

Electric charge in coulombs
Distance from charge
Type of charge distribution
Dielectric medium

Enter charge details and click Calculate to see results

About Electric Potential Calculator

The Landscape of Charge: The Ultimate Guide to Our Electric Potential Calculator

Imagine the universe of electric charges as a landscape. Some charges, like positive protons, create "hills," while others, like negative electrons, create "valleys." Navigating this landscape requires energy. To push a positive test charge up a hill created by another positive charge requires work. This work isn't lost; it's stored as potential energy, ready to be released. The "height" of any point in this electrical landscape is what physicists call **Electric Potential**.

Electric potential, more commonly known as **voltage**, is one of the most fundamental and crucial concepts in all of electricity and electronics. It is the driving force that makes charges move, creating current. It is the measure of potential energy per unit charge, a property of space itself created by the presence of other charges.

Welcome to the definitive guide to this foundational concept. Our Electric Potential Calculator is a tool designed to help you quantify this "electrical height" created by a point charge. This comprehensive article will not only guide you through the calculator's use but will also explore the deep connections between electric potential, potential energy, electric fields, and the everyday concept of voltage.

Electric Potential vs. Electric Potential Energy: A Critical Distinction

These two terms sound very similar but describe different things. The distinction is analogous to the difference between a gravitational field and the gravitational potential energy of an object within it.

Electric Potential Energy (U)

This is the potential energy that a **specific charge** (`q`) possesses due to its position in an electric field. It's the work done to bring that charge from a reference point to its current location. It is a property of the *system* of charges and is measured in **Joules (J)**. It depends on the charge you are placing in the field.

Electric Potential (V)

This is a property of a **point in space** itself, created by a source charge. It is defined as the electric potential energy *per unit charge*. It tells you how much potential energy a charge of +1 Coulomb would have if it were placed at that point. It is measured in **Volts (V)**, where `1 Volt = 1 Joule per Coulomb`. It is independent of the charge you might place there later.

The relationship is simple:

V = U / q   or   U = q * V

Electric potential (voltage) creates the "landscape," and the potential energy is how much energy a specific charge "gains" or "loses" by being at a certain height on that landscape.

The Formula for Electric Potential from a Point Charge

The electric potential at a certain distance from a single point charge is the foundation for most calculations. Our calculator is built upon this fundamental formula.

V = k * (Q / r)

Let's break down each component of this equation:

  • V is the **Electric Potential** at the point of interest, in Volts (V).
  • k is **Coulomb's Constant**, a fundamental physical constant. Its value is approximately **8.987 × 10⁹ N·m²/C²**.
  • Q is the magnitude of the **source charge** creating the potential, in Coulombs (C). Unlike in the force equation, the sign of this charge is important. A positive charge creates a positive potential ("hill"), and a negative charge creates a negative potential ("valley").
  • r is the **distance** from the source charge to the point where the potential is being measured, in meters (m). Notice that `r` is **not squared**, unlike in the formula for electric force or electric field.

This formula tells us that the potential gets stronger as you get closer to the source charge and weaker as you move away, falling off as `1/r`.

How to Use the Electric Potential Calculator

Step 1: Enter the Source Charge (Q)

Input the magnitude of the charge that is creating the electric potential. Remember to include the sign (+ or -). The unit is Coulombs (C). A single proton or electron has a charge of `±1.602 × 10⁻¹⁹ C`.

Step 2: Enter the Distance (r)

Input the distance from the center of the source charge to the point in space where you want to calculate the potential. This must be in meters (m).

Step 3: View the Result

The calculator will instantly apply the formula `V = kQ/r` and provide the electric potential at that point in **Volts (V)**.

Potential Difference: What Makes Current Flow

In practice, the absolute value of the electric potential at a single point is often less important than the **potential difference** between two points. This is what we commonly call **voltage**.

ΔV = V_final - V_initial

A potential difference is what compels charges to move. Positive charges will naturally "roll downhill" from a region of high potential to a region of low potential. Negative charges, like electrons, will do the opposite, "rolling uphill" from low potential to high potential. This directed movement of charge is what we call **electric current**. A 9-volt battery, for example, maintains a potential difference of 9 Volts between its positive and negative terminals, creating the "electrical pressure" to drive a current through a circuit.

Worked Example: Potential Difference

A positive source charge of +2 microcoulombs (+2 × 10⁻⁶ C) is at the origin. What is the potential difference between a point A, located 0.5 m away, and a point B, located 1.5 m away?

  • Step 1: Calculate Potential at A (V_A).
    `V_A = (8.987e9) * (2e-6) / 0.5 = 35,948 V`.
  • Step 2: Calculate Potential at B (V_B).
    `V_B = (8.987e9) * (2e-6) / 1.5 = 11,983 V`.
  • Step 3: Calculate Potential Difference.
    `ΔV = V_B - V_A = 11,983 - 35,948 = -23,965 V`.
  • Result: The potential difference is -23,965 Volts. This means a positive charge would have to have 23,965 Joules of work done on it *per Coulomb* to move it from point A to point B against the electric field.

The Relationship with the Electric Field

Electric Potential (a scalar) and the Electric Field (a vector) are intimately related. The electric field can be thought of as the "steepness" or gradient of the electric potential landscape.

  • The electric field vector `E` always points in the direction of the steepest decrease in electric potential `V`.
  • Lines of constant potential, called **equipotential lines**, are always perpendicular to the electric field lines.
  • In a uniform electric field, the potential difference is simply `ΔV = -E * d`, where `d` is the distance moved parallel to the field.

Frequently Asked Questions (FAQ)

Q: Why isn't the distance `r` squared like it is for electric force?

This is a great question that gets to the heart of the definitions. Electric Potential Energy (`U = kQq/r`) is the integral of the Electric Force (`F = kQq/r²`) with respect to distance. Integrating a `1/r²` term gives a `1/r` term. Since Electric Potential `V` is just `U/q`, it also has the `1/r` dependence.

Q: What if I have multiple source charges?

This is where the power of potential as a scalar quantity shines. To find the total potential at a point due to multiple charges, you simply calculate the potential from each charge individually and then **add them up as numbers**. You don't need to worry about vector components like you do when adding electric fields. This is called the principle of superposition.

Mapping the Invisible Forces

Electric potential is one of the most powerful and abstract concepts in electromagnetism. It provides a scalar "map" of the electrical landscape, allowing us to easily calculate the energy changes and forces on charges moving within it. It is the foundation upon which all of circuit theory is built.

Use our calculator to explore this landscape. See how the potential changes with distance and with the strength of the source charge. Calculate the voltage at different points in space and begin to build an intuition for the invisible "heights" and "valleys" that dictate the flow of energy in our electronic world.

Frequently Asked Questions

What is electric potential?
Electric potential (voltage) is the amount of electric potential energy per unit charge at a point in an electric field, measured in volts (V).
How is electric potential calculated for a point charge?
V = kQ/r, where V is potential, k is Coulomb's constant (8.99×10⁹ N·m²/C²), Q is charge, and r is distance from the charge.
What's the difference between electric potential and electric potential energy?
Potential is energy per charge (V = U/q). Potential energy (U) depends on both the field and test charge, while potential depends only on the source charges.
How do I calculate electric potential from an electric field?
V = -∫E·dl (line integral of electric field along a path). For uniform fields: ΔV = -Ed, where d is distance in field direction.
What is the electric potential due to multiple point charges?
Sum the potentials from each charge: V_total = kΣ(qᵢ/rᵢ). Potential is a scalar, so simple addition works (no vector components needed).
How is electric potential related to work?
Work done moving charge q through potential difference ΔV is W = qΔV. 1 electron-volt (eV) = work to move 1e through 1V = 1.6×10⁻¹⁹ J.
What is the potential at infinity in calculations?
By convention, potential is zero at infinity for localized charge distributions. This reference point makes potential calculations meaningful.
How do I calculate equipotential surfaces?
Surfaces where V is constant. For point charge: concentric spheres. For dipole: more complex surfaces perpendicular to field lines.
What is the electric potential inside a conductor?
Constant throughout (equipotential). No potential difference means no electric field inside static conductors.
How is potential calculated for continuous charge distributions?
Integrate dV = kdq/r over the distribution. For line charge: V = k∫λdl/r. Surface charge: V = k∫σdA/r. Volume charge: V = k∫ρdV/r.
What is the potential of a charged sphere?
Outside: V = kQ/r (like point charge). Inside conducting sphere: constant V = kQ/R. Inside insulating sphere: V = kQ(3R²-r²)/(2R³).
How does electric potential relate to capacitance?
C = Q/ΔV. Capacitance measures how much charge a system stores per volt of potential difference between conductors.
What is the potential difference in a uniform electric field?
ΔV = -Ed, where E is field strength and d is displacement parallel to field. Moving along equipotentials gives ΔV = 0.
How do I calculate potential energy from electric potential?
U = qV. For multiple charges: U = ½ΣqᵢVᵢ (factor of ½ avoids double-counting pairwise interactions).
What is the electric potential of an electric dipole?
V = kp·r̂/r² (far field), where p is dipole moment (qd), r̂ is unit vector from dipole center, and r >> d (dipole separation).
How is potential calculated for parallel plates?
Between plates: ΔV = Ed, where E = σ/ε₀ (σ is surface charge density, ε₀ is permittivity). Outside: potential falls off rapidly.
What is the potential at the midpoint between two equal charges?
For same-sign charges: V = 2kQ/r (add potentials). For opposite charges: V = 0 (equal and opposite potentials cancel).
How does grounding affect electric potential?
Grounding sets V = 0 at that point. All potentials are then measured relative to ground potential.
What is the potential energy of a charge system?
Work needed to assemble the configuration: U = kΣ(qᵢqⱼ)/rᵢⱼ for all pairs (i<j). For continuous distributions: U = ½∫ρVdV.
How is potential calculated for a ring of charge?
On axis: V = kQ/√(z²+R²), where Q is total charge, R is ring radius, z is axial distance. Off-axis requires numerical integration.
What is the potential of an infinite line of charge?
V = -2kλln(r/r₀), where λ is linear charge density, r is distance, r₀ is arbitrary reference distance (potential diverges at ∞).
How do I find electric field from potential?
E = -∇V (negative gradient of V). In 1D: E = -dV/dx. In 3D: E_x = -∂V/∂x, etc. Field lines point downhill on potential surfaces.
What is the potential of an infinite plane of charge?
V = -σ|z|/(2ε₀) + C, where σ is surface charge density, z is perpendicular distance, C is integration constant (potential diverges with distance).
How is potential calculated for a charged disk?
On axis: V = 2πkσ(√(z²+R²) - |z|), where σ is surface charge density, R is disk radius, z is axial distance.
What is the potential inside a capacitor?
Between plates: varies linearly from V at one plate to 0 at the other (ΔV = Q/C). Outside: approximately zero for parallel plate capacitors.
How does potential vary in a circuit?
Drops across resistors (V=IR), constant along ideal wires. Battery increases potential by its emf. Kirchhoff's rules govern potential changes.
What is the potential of a spherical shell?
Outside: V = kQ/r. On surface: V = kQ/R. Inside: same as surface (constant for conductors, varies for insulators with internal charge).
How is potential calculated for a charged cylinder?
Outside: V = -2kλln(r/r₀) (like line charge). Inside depends on charge distribution - constant for conducting cylinder with surface charge.
What is the potential energy of an electron in an atom?
U = -ke²/r (hydrogen atom), where e is electron charge, r is orbital radius. Negative because bound states have lower energy than free electrons.
How does potential behave at sharp conductors?
Potential remains constant (conductors are equipotentials), but electric field and surface charge density are highest at sharp points.
What is the potential of a quadrupole?
V ≈ k(Qr² + D·r̂)/r³ far away, where Q is quadrupole moment tensor and D is dipole moment (if present). Falls off faster than dipole potential.
How is potential calculated in dielectric materials?
Modified by relative permittivity κ: V = V₀/κ. Polarization creates bound charges that alter the potential distribution.
What is the potential at a conductor-dielectric boundary?
Potential is continuous across boundary. Normal E field discontinuous by factor of κ (relative permittivity).
How does potential vary in a plasma?
Plasmas tend toward quasi-neutrality, creating complex potential distributions. Debye shielding makes potentials fall exponentially over Debye length.
What is the potential of a charged ellipsoid?
Outside: complex expression involving elliptic integrals. Special cases: sphere (r⁻¹), needle (lnr/r), disk (tan⁻¹(√(R²/ρ²-1))/ρ).
How is potential calculated in electrochemical cells?
Nernst equation gives potential difference: E = E° - (RT/nF)lnQ, where Q is reaction quotient, n is electrons transferred.
What is the potential inside a p-n junction?
Built-in potential V_bi ≈ (kT/e)ln(NₐN_d/nᵢ²), where Nₐ,N_d are doping concentrations, nᵢ is intrinsic carrier density.
How does potential behave in superconductors?
Perfect conductors maintain constant potential throughout. Magnetic flux quantization creates periodic potential variations in type-II superconductors.
What is the potential of a charged torus?
Complex calculation requiring elliptic integrals or numerical methods. Approximations exist for large/small aspect ratios.
How is potential calculated in molecular systems?
Quantum mechanical methods solve for electrostatic potential from electron clouds and nuclei. Often visualized as isopotential surfaces.
What is the potential near a lightning rod?
Follows conductor potential until breakdown. During discharge, potential gradient becomes extremely steep near the tip.
How does potential vary in the Van de Graaff generator?
High potential builds on the dome (MV range). Potential falls off roughly as 1/r outside, constant inside the conducting dome.
What is the potential of a charged fractal?
Depends on fractal dimension. Complex distributions create intricate potential landscapes, often requiring numerical computation.
How is potential calculated in semiconductor devices?
Solve Poisson's equation ∇²V = -ρ/ε with appropriate boundary conditions and charge distributions (doping profiles, etc.).
What is the potential inside a Faraday cage?
Constant throughout (same as cage potential). External fields create surface charges that cancel fields inside.
How does potential behave in atmospheric electricity?
Potential increases with altitude (~100 V/m near surface). Thunderstorms create large potential differences (100s of MV) in the atmosphere.