Ohm's law


Ohm's law is a scientific formula that establishes the relationship between current, voltage, and resistance in an electrical circuit.

The electrical circuits always have the same operation, the current leaves the power supply and runs through the entire circuit. What Ohm's law measures is how the three variables involved in this operation are related.

The formula was developed by the physicist and mathematician Georg Simon Ohm in the 19th century. In his research he discovered electrical resistance. So as a result and in his honor, this is measured in ohms.

Formula components

The three variables involved in the formula developed by Ohm are the following:

  • Current: "It is the physical quantity that expresses the amount of electricity that flows through a conductor in a unit of time." It is measured in amps
  • Voltage: It is the difference that exists between the electrical charge that leaves the source and with which it finally reaches the end of the circuit. It is expressed in volts and is a fixed value.
  • Endurance. It was the variable discovered by Ohm, and it is the "difficulty that a circuit opposes to the passage of a current." In other words, when the electric charge passes through the conductive material of the circuit, it “slows down”, since that is the resistance. They are measured in ohms.

Ohm's law formula

Ohm's law formula states that current equals voltage divided by resistance.

The consequences that are drawn from it is that the higher the voltage and the lower the resistance, the greater the intensity of the current, the greater the number of amps. And the higher the resistance and the lower the voltage, the lower the electric current. Due to the simplicity of the formula, knowing two pieces of information we can know the third.

Thus, in the first formula, knowing the current and the resistance we can obtain the voltage. And in the one on the right, knowing the voltage and the current, the intensity value can be obtained.


If we have an electrical appliance whose voltage is 120v and its resistance is 40 ohms. What is the intensity of the current?

  1. I = V / R It is the formula of Ohm's law that we need.
  2. I = 120/40 We put in the formula the values ​​that the statement has given us.
  3. 120/40 = 3 We carry out the division with 3A (amps) being the solution to the problem.

The process would be the same depending on the variable that we have to clear, the values ​​are substituted in the formula and it is executed.

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