ohm triangle

An intro about Ohm’S LAW

Ohm’s Law is among the most fundamental and significant laws regulating electronic and electrical circuits. It relates current, voltage, and resistance for a linear device, such that if two understand, the third could be calculated.

With current, resistance, and voltage being three of the significant circuit quantities, this means that Ohm’s Law is also hugely significant.

Ohm’s Law is used within all branches of electronic and electrical science. It’s used for calculating the value of resistors required in circuits, and it can also be used for ascertaining the current flowing in a circuit in which the voltage could be measured easily across a known resistor, but more than that, Ohm’s Law is used in a huge number of calculations in all sorts of electric and electronic circuit- in fact anywhere that flows.

Georg Ohm

Georg Simon Ohm was a German physicist and mathematician. As a college teacher, Ohm started his study with the new electrochemical cell, invented by Italian scientist Alessandro Volta. Utilizing gear of his own creation, Ohm discovered that there’s a direct proportionality between the potential difference (voltage) applied across a conductor as well as the resultant electrical current. This relationship is called Ohm’s law.

Ohm’s Law

Ohm’s Law describes how current flows through a substance when different levels of voltage are implemented. Some substances like electric wires present little resistance to the flow and this sort of material is known as a conductor. Hence if this conductor is placed right across a battery by way of instance, plenty of current would flow.

In other cases, another substance may impede the flow of current, but still, allow some though. In electric circuits, these elements are often called resistors. Yet other substances let virtually no current though and these are called insulators.

Ohm’s Law Statement

The most basic elements of power are voltage, current, and resistance. Ohm’s law demonstrates a very simple relation between these three quantities. Ohm’s law states that the current through a conductor between two factors is directly proportional to the voltage across the two points.


Resistance is a measure of the opposition to current flow in an electrical circuit. Measured in ohms, represented by the Greek letter omega (Ω). Ohms are named after Georg Simon Ohm.


Current is the flow of electric charge carriers such as electrons. Electrical current flows from negative to positive points. The SI unit for measuring electrical current is the ampere (A). 1 ampere of current is described as one coulomb of electric charge moving past a special point in a second. Electric current is broadly used in household and industrial appliances.


Voltage is the pressure from an electric circuit’s power source that pushes energized electrons (current) through a running loop, allowing them to perform work like illuminating a light.

In summary, voltage = pressure, and it’s measured in volts (V). The term acknowledges Italian physicist Alessandro Volta (1745-1827), inventor of the voltaic pile–the forerunner of the battery.

Ohm’s Law formula

Ohm’s Law formula or equation is extremely straightforward.

Ohm’s law can be demonstrated in a mathematical form:


ohm formula


  • V = voltage shown in Volts
  • I = current shown in Amps
  • R = resistance shown in Ohms
Ohms Law Triangle

Transposing the Normal Ohms Law equation above will give us the following mixtures of the same equation:

ohm triangle

Then by using Ohms Law we can see a voltage of 1V applied to a resistor of 1Ω will cause a current of 1A to flow and the larger the resistance value, the less current which will flow for a given applied voltage.

ohmic devices

The system which follows ohm’s law for all voltages across it’s called an ohmic device. (i.e under continuous physical conditions like temperature, the resistance is constant for many currents that pass through it). Cases of ohmic devices are: a cable, heating element, or a resistor.

non-ohmic device

The system that doesn’t follow ohm’s law is called a non-ohmic apparatus (i.e. the resistance differs for different currents passing through it). Cases of non ohmic devices are: thermistors, crystal rectifiers, vacuum tube etc.

Derivation of Ohm’s Law


We know, based on Ohm’s Law,



R=ρl​ /A



​Current per unit area (taken normal to the current), I/A, is called current density and is denoted by j.

Further, if E is the size of the uniform electric field in the conductor whose length is l, then the potential difference V across its ends is El.


the above equation can also be casted in vector form. The current density (current through unit area normal to the present) is also guided along and can also be a vector J.

Hence the above equation can be casted in vector form as


​where σ= 1/ρIs known as the conductivity.


Conductivity is the measure of the ease at which an electrical charge can pass through a material. A conductor is a material that gives hardly any resistance to the flow of an electric current.


Let resistance used for verification be R. Create a circuit of R, voltmeter, and ammeter measuring voltage and current through R, rheostat (variable resistor), and a cell. Connect the components correctly. Note down values of voltage and current shown by voltmeter and ammeter. Repeat the above for different values of Rheostat. Record data in a tabular format and compute


For each instance. It should be roughly the same. Plot V v/s I on a chart paper. A straight line is obtained whose slope equals immunity.

ohm v sl

Electrical Power and Ohms Law

By using Ohm’s law and substituting for the values of V, R, and I the formula for Electric power Are Available as:

To find the Power (P)

[ P = V x I]      P (watts) = V (volts) x I (amps)


[ P = V2 ÷ R]      P (watts) = V2 (volts) ÷ R (Ω)


[ P = I2 x R]   P (watts) = I2 (amps) x R (Ω)

Again, the three quantities are superimposed to a triangle this time called a Power Triangle with electricity on top and voltage and current at the bottom. Again, this arrangement reflects the actual position of each quantity within the Ohms law power formulas.

The Power Triangle

ohm power triangle

Implementation of Ohm’s Law

There are thousands of uses of this law in our everyday life. We will show only some of them in this guide.

  • Traditional Domestic Fan Regulator is one very common device where the current through the fan gets regulated by controlling the resistance of the regulator circuit.
  • In a voltage divider circuit, this law is used to split source voltage across the output resistance.
  • In digital circuits, there are many functions where intentional voltage drop is required to supply specific voltage across different electronic elements. This is accomplished by applying Ohm’s law.