# Differences between voltage and current

There are two key circuit quantities in electric circuit theory. Current and voltage. These circuit quantities are very important to study in electric circuits.

The followings are the differences between voltage and current:

Table of Contents

## Definitions

**Electricity is the flow of electrons in a conductor from one atom to the next atom in the same general direction. This flow of electrons is referred to as current. The current that constantly flows in the same direction is called direct current (DC). The current that periodically changes direction is called alternating current (AC). **

The force that causes current to flow through a conductor is called a difference in potential, electromotive force (emf), or voltage. A voltage can be generated in various ways. A battery uses an electrochemical process. A car’s alternator and a power plant generator utilize a magnetic induction process. All voltage sources share the characteristic of an excess of electrons at one terminal and a shortage at the other terminal. This results in a difference of potential between the two terminals.

For a DC voltage source, the polarity of the terminals does not change, so the resulting current constantly flows in the same direction. The terminals of an AC voltage source periodically change polarity, causing the current flow direction to change with each switch in polarity.

## Causes

Current is caused by the motion of electrons. Voltage is caused by the potential difference between two points.

## Units

Current is measured in amperes, which is often shortened to “amps”. The letter I” is the symbol for amps. 1 ampere is 6.241×10¹⁸ electrons per second.

The unit of measurement for voltage is “volts” which is also designated by the letter “V.”

## Formulas

As voltage increases, the current increases. Voltage and current are proportional, while the resistance remains constant.

V = I x R

If voltage is constant, the current decreases as resistance increases.

I = V / R

## Relationship

Current is the effect. Current cannot flow without voltage. Current is a measure of the rate of flow of electric charge through a circuit. A large current means a faster rate of flow. Current can be changed by increasing or decreasing the voltage of the circuit.

## Scientists

The unit “volt” is named after the Italian physicist Alessandro Volta who invented what is considered the first chemical battery. The I symbol was used by André-Marie Ampère, after whom the unit of electric current is named, in formulating Ampère’s force law.

## SI Units

SI unit of the voltage is “volt” but the SI unit of the current is “ampere”.

## Symbols

Current is designated by the symbol “I”. Voltage is designated by the letter “E” or the letter “V.”

## Measuring instruments

Current can be measured using an ammeter but voltage can be measured using a voltmeter. The ammeter must be connected in series with the circuit to measure current. The voltmeter should be connected in parallel with the circuit component to measure voltage. When using a voltmeter to measure potential difference, one electrical lead of the voltmeter must be connected to the first point, one to the second point.

## Series connection

The equation for total resistance in a series circuit allows us to simplify a circuit. Using Ohm’s Law, the value of current can be calculated. Current is the same anywhere it is measured in a series circuit. Voltage gets distributed over components connected in series.

## Parallel connection

When resistors are placed in parallel across a voltage source, the voltage is the same across each resistor. Current gets distributed over components connected in parallel.

## Field created

An electric current always produces a magnetic field. The stronger the current, the more intense is the magnetic field. A voltage produces an electrostatic field. As the voltage increases between two points, the electrostatic field becomes more intense.