Ohm’s law is the most important law that shows the dependence between the characteristics of electric current in a circuit or part of a circuit! Ohm’s law describes the dependence between:

  • The electric voltage
  • The strength of the electric current
  • The electrical resistance

Definition of Ohm’s law

Ohm’s law reads: The strength of the electric current is directly proportional to the electric voltage and inversely proportional to the electric resistance!

Ohm’s law is often interpreted as: The quotient between the electric voltage and the strength of the electric current in a given circuit is a constant (invariable) value, which actually represents its electrical resistance!

Formula for Ohm’s law

The formula with which we can express Ohm’s law is:

Ohm's law formula

The other two transformations from the basic formula that we get by transforming the basic formula for Ohm’s law are:

Formula by which the electric voltage can be calculated through the strength of the electric current and the electric resistance:

Ohm's low Electrical voltage from amperage and electrical resistance

Formula with which we can calculate the electrical resistance through the electrical voltage and the strength of the electrical current:

Ohm's law Electrical resistance from amperage and electrical voltage

Examples with simple tasks

Example 1. Calculate the electrical resistance of a circuit in which, under the influence of an electrical voltage of 220 volts, an electrical current of 2 amperes flows.

To calculate the electrical resistance of a circuit using this law, we apply the third transformation of the formula from this page. After replacing the values in the formula, it looks like this:

Calculation of resistance according to Ohm's law

Finally, it is enough to divide the values, which gives the final value of the electrical resistance, which is:

110 Ohms

Example 2: Calculate the strength of the electric current that flows in a circuit under the influence of an electric voltage of 15 volts, if the circuit has an electrical resistance of 12 ohms.

To calculate the strength of the electric current, we apply the first formula for the law from this page. After replacing the values in the formula, it looks like this:

Calculation of current strength according to Ohm's law

After dividing the values, we get the final value for the strength of the electric current, which is:

1.24 amps

Video examples

The video below contains three examples of solved problems using this law:

Ohm's law examples

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