An electrical circuit is a complete path through which electrons flow. A circuit must have a power source, such as a battery, and a load, such as a light bulb, that uses the electricity. The load is connected to the power source by conductors, such as wires.

## Ohm’s Law Equation

If you know the voltage of the power source and the resistance of the load, you can calculate the current flowing through the circuit using the equation:

Current (I) = Voltage (V) / Resistance (R)

**This is called Ohm’s law equation.**

If the power source is an alternating current (AC) rather than a direct current (DC), you must use a slightly different equation:

Current (I) = Voltage (V)/Reactance (X)

Reactance is a measure of the opposition to current flow caused by the circuit’s inductance or capacitance.

If you know the current flowing through the circuit and the voltage of the power source, you can calculate the resistance of the load using the equation:

Resistance (R) = Voltage (V) / Current (I)

If you know the current flowing through the circuit and the reactance of the circuit, you can calculate the voltage of the power source using the equation:

Voltage (V) = Current (I) x Reactance (X)

These equations are all you need to solve most circuit problems. However, one more equation is sometimes needed, and that is the equation for impedance.

Impedance (Z) is the total opposition to current flow in a circuit, and it is equal to the sum of the resistance and reactance.

Impedance (Z) = Resistance (R) + Reactance (X)

If you know the voltage of the power source and the current flowing through the circuit, you can calculate the impedance using the equation:

Impedance (Z) = Voltage (V) / Current (I)

Once you know the impedance, you can use the other equations to calculate the voltage, current, or resistance.

This article has explained the four most important equations for solving circuit problems. These equations are:

**Ohm’s law:**

Current (I) = Voltage (V) / Resistance (R)

The equation for impedance:

Impedance (Z) = Resistance (R) + Reactance (X)

The equation for voltage:

Voltage (V) = Current (I) x Reactance (X)

The equation for current:

Current (I) = Voltage (V) / Reactance (X)

I=V/X…