Ohm’s Law. Equation and applications

23/04/2026

The online Ohm’s Law simulations on this page will allow you to learn in a practical way how this important law works and how it shows us the relationship between voltage, current and resistance. We will discover what Ohm’s law equation is and some of its most important applications.

This Thematic Unit is part of our Physics collection

Current Intensity

Amount of electric charge passing through a cross-section of the conductor per unit of time, measured in Amperes (A).

Non-Ohmic Material

Material or device whose resistance varies depending on the voltage or current applied, not following a straight line in its V-I graph.

Ohm’s Law

Fundamental principle stating that current intensity is directly proportional to voltage and inversely proportional to resistance: V = I · R.

Ohmic Material

One that exhibits a constant linear relationship between the applied voltage and the resulting current, keeping its resistance fixed.

Voltage (Tension)

Electric potential difference between two points in a circuit that drives the movement of charges, measured in Volts (V).

Voltage Drop

Decrease in electric potential when passing through a resistive component due to the energy consumption of the charges.

What is Ohm’s law

Ohm’s law is a fundamental law in physics that describes the relationship between electric current, resistance and voltage in an electric circuit. It was formulated by the German physicist Georg Simon Ohm in 1827 and has become one of the fundamental concepts in the study of electricity.

Ohm’s law Equation

Ohm’s law states that the electric current flowing through a conductor is directly proportional to the applied voltage and inversely proportional to the resistance of the conductor. Mathematically, Ohm’s Law equation is expressed as

I = V/R

where

I is the current in amperes

V is the voltage in volts

R is the resistance in ohms

This means that if the voltage applied to a circuit is increased, the current will also increase, as long as the resistance remains constant. Similarly, if the resistance is increased, the current will decrease, as long as the voltage remains constant.

Ohm’s law applications

Ohm’s law is especially useful in the design and analysis of electrical circuits. It allows you to determine the current that will flow through a given component, as well as the voltage drop that will occur across that component. It is also used to calculate the resistance needed to limit the current in a circuit, or to determine the voltage needed to obtain a desired current. In addition to its basic formulation, Ohm’s law can be applied to different components in a circuit, such as series or parallel resistors.

Current Intensity

Amount of electric charge passing through a cross-section of the conductor per unit of time, measured in Amperes (A).

Non-Ohmic Material

Material or device whose resistance varies depending on the voltage or current applied, not following a straight line in its V-I graph.

Ohm’s Law

Fundamental principle stating that current intensity is directly proportional to voltage and inversely proportional to resistance: V = I · R.

Ohmic Material

One that exhibits a constant linear relationship between the applied voltage and the resulting current, keeping its resistance fixed.

Voltage (Tension)

Electric potential difference between two points in a circuit that drives the movement of charges, measured in Volts (V).

Voltage Drop

Decrease in electric potential when passing through a resistive component due to the energy consumption of the charges.

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Ohm's law simulations

Equation
Measurements
Bulb

Ohm’s Law equation

See how the form of Ohm’s law equation relates to a simple circuit. Adjust the voltage and resistance and see the change in current according to Ohm’s law.

Measuring voltage, current and resistance

Experiment with a light bulb

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“Science is the explanation of the complex by the simple”

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Test your knowledge

What does Ohm’s Law state, and why is it considered a foundational principle in the study of electrical circuits?

Ohm’s Law states that the electric current flowing through a conductor is directly proportional to the voltage applied across it and inversely proportional to its resistance. In its most familiar form, it is expressed as 𝑉 = 𝐼 ⋅ 𝑅 , where voltage is measured in volts, current in amperes, and resistance in ohms. This relationship is foundational because it provides a simple and reliable way to predict how a conductor will behave under different electrical conditions. It allows engineers and physicists to analyze circuits, calculate energy consumption, design electronic components, and understand how materials respond to electric fields. Historically, Georg Simon Ohm established this relationship in the nineteenth century after studying how different metals reacted to applied voltages, and his work remains central to modern electrical science.

How should the relationship between voltage, current, and resistance be interpreted physically, and what does it reveal about the behavior of conductive materials?

The relationship between these three quantities describes how easily electric charge can move through a material. Voltage acts as the driving force that pushes electrons, current represents the flow of those electrons, and resistance expresses the internal opposition that the material presents to that flow. If the voltage increases while resistance remains constant, the current increases proportionally. If the resistance increases, the current decreases even if the voltage stays the same. This linear behavior is characteristic of materials known as ohmic conductors, where the ratio 𝑉 / 𝐼 remains constant. However, not all materials behave this way, which shows that Ohm’s Law is extremely useful but not universal.

Why does the current increase when I raise the voltage? Shouldn’t there be some natural limit that stops it from growing?

The current increases because voltage is essentially the electrical pressure that pushes electrons through the conductor. When that pressure rises, more electrons move per unit of time, which means the current increases. The limit is not set by Ohm’s Law but by the physical properties of the material. If the voltage becomes too high, the conductor heats up, its structure may change, and eventually it can melt or break. Under normal conditions, though, the increase in voltage produces a proportional increase in current as long as the material continues to behave linearly.

Why don’t all materials obey Ohm’s Law? Shouldn’t every conductor follow the same rule?

Not all materials respond linearly to voltage. In some materials, the resistance changes with temperature, with the intensity of the current, or with the applied voltage itself. Devices such as diodes, incandescent bulbs, and many semiconductors do not show a proportional relationship between voltage and current. Their internal structure or operating principles cause them to behave differently, so the ratio 𝑉 / 𝐼 is not constant. Ohm’s Law accurately describes many metals under ordinary conditions, but it was never intended as a universal rule for all conductive materials.

Why does resistance reduce the amount of current that can flow? What is happening inside the material?

Resistance reflects the difficulty electrons encounter as they move through the material. Inside a conductor, electrons collide with atoms in the crystal lattice. These collisions slow them down and convert part of the electrical energy into heat. A material with high resistance has a structure that causes more frequent or more intense collisions, making it harder for electrons to move. A material with low resistance allows electrons to travel more freely. This microscopic behavior explains why metals conduct well and why insulators barely allow any current to pass.