Voltage Formula [Energy, Charge to Volts]

Voltage or potential difference is defined as the ratio between energy and charge. The voltage is actually the difference of potential between two points.

Formula for voltage

Voltage formula Calculator



Example 1: 200 J of energy is required to move a 10-coulomb charge from point a to point b. Find the potential difference between both points.

Solution: V = W/Q = 200 J / 10 C = 20 volts

Examples 2: It is desired to move a 2-coulomb charge from point b to point d. The potential difference between these points is noted to be 12 V. Find the energy which is required.

Solution: W = Q * V = 2 C * 12 V = 24 J

Example 3:  The voltage between two points is known to be 30 V. While moving an unknown charge between points the energy is found to be 100 J. Calculate the coulombs of charge.

Solution: Q = W/V = 100 J / 30 V = 3.33 C

Theory of voltage

Volts are often defined as the electrical potential difference between two points. Let’s understand the mechanical potentials first. Consider a 10 kg stone which is hoised by a crane at a certain height. When the stone is dropped from crane it reaches the earth and performs some work. The stone did some work because we first worked on it to carry it and hoise it with the crane. In other terms, we did some work and it stored the potential.

The same work is done in electrical batteries. Whenever two opposite charges are separated they store some gain a difference of electric potential. We can compare the process of charge separation with the crane lifting of stone. Now when the external source is connected the battery provides voltage to the circuit.

Practical sources

The cell in analog and digital watches: The most common example of practical V source is the cell in your analog and digital watches which provides 1.5 V to the watch.

The wall outlet in our homes: The wall outlets in our homes are ac V sources which provide 120/230 V alternating current.

Other formulas:

kW to amps: Useful formulas for calculating current from kW. It is used for dc circuits, single phase ac circuits, two, and three phase ac circuits.

Series resistor formula: It is used to solve two or more resistors in series and parallel circuit configuration.

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