ohm's law

Ohm’s Law

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In Physics, the term Ohm is a term that is often encountered. In addition to being a unit, there is also Ohm’s law which states that the electric current (I) flowing in a conductor is proportional to the potential difference (V) given at each end of the conductor wire.

It also means that the greater the potential difference, the greater the electric current flowing. Let’s dissect this material in depth.

Ohm’s Law Sound

ohm's law

“The sound of Ohm’s law states: The amount of electric current (I) flowing in the conductor (conductor) has a value that is directly proportional to the difference in potential / voltage (E) and inversely proportional to the resistance (R).”

This means that the greater the current (I) flowing in an electrical circuit, the greater the voltage value (E) produced. But this also means the smaller the resistance value (R) that exists in the electrical circuit.

To be able to learn more about the applicable law, you must first know the definition / understanding of ohm’s law and also how to calculate the formula for how to calculate it in series and parallel electrical circuits.

Ohm’s Law is a statement / formula used to calculate the relationship between voltage, current and resistance in an electrical circuit. The Ohm’s Law equation can be expressed mathematically by the formula E/I = R.

The discoverer of Ohm’s Law was a German physicist named Gerog Simon (March 16, 1789 – July 6, 1854). In his book entitled “The Galvanic Circuit Investigated Mathematically”, Gerog Simon states that Ohm’s law is the basic law of electrical circuits.

The provisions of this law relate voltage and current to the properties of conductors. In electrical circuits, ohm’s law deals with the current strength, voltage and also electrical resistance in linear devices.

In practice, this law is used to determine various things. This law can be used to calculate the amount of electric voltage, electric current strength and resistance that exists in an electrical circuit.

Basic Theory of Ohm’s Law:

Equation Symbol Unit Roles in the Series Information
Voltage And Volt (V) Pressure that triggers electron flow E = electromotive force
Current I Ampere, amp (A) Electron flow rate I = Intensity
Obstacles R Ohm (H) Flow inhibitors Ω = Greek letter Omega

The basis of Ohm’s law theory is that if two of the values are known, then we can reconfigure Ohm’s Law to calculate and configure the third.

How to Reconfigure Ohm’s Law Formula:

  1. Suppose we already know the value of knowing the voltage (E) and current (I), then we want to know the value of resistance (R), then we use the equation R = E/I.
  2. The second example suppose we already know the value of voltage (E) and resistance (R), to calculate how strong the value of current (I), we can use the equation I = E / R.
  3. The third example suppose you already know what the value of current (I) and resistance (R), then to find out the value of the voltage, we just apply the equation E = I.R

Application of Ohm’s Law:

Its widespread use of this law can be easily found in electronic circuits. This law is also the basic law in an electrical circuit.

Not only used to calculate the amount of electric voltage, electric current and resistance in an electrical circuit, this law can also be used for other needs.

In practice its use in an electrical circuit, the function of Ohm’s law can also be used to reduce electric current and voltage and obtain the required resistance value.

With all these uses, knowing the law and how to calculate it then becomes the next important thing to learn. Here we also include the main functions of this law:

  • Determine the voltage, resistance or current of an electrical circuit.
  • Maintains the desired voltage drop across electronic components.
  • Application to DC ammeters and other DC shunts to divert current.

Limitations of Ohm’s Law:

Although widely used, this law also has limitations. The initial assumption of this law was that resistance does not depend on current. That way, the resistance will always remain, independent of the Current.

Therefore, this law cannot be applied to insulators, semiconductor materials or to fluids. These materials became known as non-Ohmic materials because Ohm’s law does not apply.

This law also does not apply to unilateral electrical elements such as diodes and transistors because it allows current to flow through one direction only. For non-linear electrical elements with parameters such as capacitance, resistance etc., voltage and current will not be constant with respect to time making it difficult to use this law.

Read Also Star Delta Motor 3 Phase Circuit Example

Ohm’s Law Formula

ohm's law

Based on International units, mathematically the ohm law formula is R = E/I, where E = voltage with units of Volt (V), I = current strength with units of  Amp (A), and R = Resistance with units of ohms (Ω).

To make it easier to remember this formula, you can use the triangular formula chart that we have presented above. The trick, if you want to find the formula of one of them, just close the letter that symbolizes what you want to find. Then you can more easily remember it.

From the formula of Ohm’s law that has been described above, the equation can be calculated using the following three equations:

  • Formula for Calculating Electric Voltage

Ohm’s law is the formula used to find the voltage of a circuit. Here’s the formula used:

E = I x R

  • Formula for Calculating Electric Current

Still related to Ohm’s law, the next thing that is calculated from an electric circuit is the electric current that flows. Electric current is the number of electrons that pass through a conductor every one second. To calculate the electric current is used the formula:

I = E/R

  • Formula for Calculating Electrical Resistance

In an electrical circuit it is also necessary to calculate the resistance. So to calculate the electrical resistance in an electronic circuit the formula is used:

R = E/I


E = potential or voltage difference in units of Volt (V)

I = electric current flowing in units of Amperes (A)

R = resistance with Ohms (Ω)

According to the ohm’s law journal written in Academia.edu, the factor that affects the magnitude of current and voltage is the resistance. The magnitude of the current strength is equal to the magnitude of the voltage, the greater the voltage, the greater the current strength. While the greater the resistance, the smaller the current.

Examples of Ohm’s Law Problems

To understand more about this law, some examples of Ohm’s law problems will help in understanding how the formula applies to the example problem. Consider the following example problem.

  • Take a look at the picture of the series below! What is the value of current strength (I) in the circuit?

ohm's law


Known : Voltage (E) = 12 V , Resistance (R) = 6 Ω

Current Strength (I) = I = E/R = 12V/6Ω = 2A

  • Pay attention to the picture of the series electric circuit below! What is the value of Resistance (R) in the circuit?

ohm's law


Known : Voltage (E) = 24 V , Strong Current (I) = 6 A

hambatan (R) = E/I = 24V/6A =

  • Pay attention to the picture of the series electronics series below! What is the value of Voltage (E) in the circuit?

ohm's law


Known : Resistance (R) = 8 Ω , Strong Current (I) = 5 A

Tegangan (E) = I x R = (5A). (8Ω) = 40 V

  • An electrical circuit has a voltage of 20V with a strong electric current of 4A. Determine the resistance value of the circuit!


Known V = 20V

I = 4A

R = V/I = 20/4 = 5 Ohm

  • It is known that in an electrical circuit with a voltage of 24 Volts an electric current of 10mA flows. What is the resistance value in the electrical circuit?



I = 10mA = 0.01A

R = V/I = 24 / 0.01 = 2400 Ohm

  • A simple electrical circuit has a voltage of 10Volt and a resistance of 10 Ohms. Hiung the magnitude of the electric current in the circuit!


V = 10 volts

R = 10 ohms

I = V/R = 10/10 = 1 A


Ohm’s law can be used to validate the static values of components in electronic circuits which include current levels, voltage supply, and voltage value drops.

For example, if a test instrument detects a higher-than-normal current measurement, it could mean that the resistance value has decreased or increased, causing a high-voltage situation. This could indicate a supply problem or on the circuit.

In a direct current (dc) circuit, a lower-than-normal electric current measurement may mean that the voltage has decreased, or the circuit resistance has increased.

Possible causes of increased resistance are poor or loose connections, corrosion or damaged components.

During the test, if we find that ordinary values are not registered on electrical measuring instruments such as multimeters or voltmeters, we can use Ohm’s Law to detect which part of the electrical circuit is experiencing trouble.

A brief and clear explanation of the entire material above may help you understand and solve examples of problems related to this law. You can download various Ohm law practicum pdf reports  to get a more complete reference on this material.

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