Difference between Voltage and Current

Differences Digital Electronics Electronics & Electrical

Voltage and current are the two fundamental electrical quantities. The voltage is the factor in an electric circuit which causes electric current to flow in the circuit. The magnitude of the voltage and current depend upon each other. However, there are several differences between voltage and current which are described in the comparison chart below.

What is Voltage?

The difference in the electric potential between two points in an electric circuit is known as voltage. The voltage is also known as potential difference or electric pressure or electric tension. If the work done in moving a unit positive charge (Q) from one point to another in the electric field is W joules, then the voltage between two points is given by,

$$\mathrm{\mathrm{Voltage,}\mathit{V}\:=\:\frac{\mathrm{Work\: done\mathrm{\left ( \mathit{W} \right )}}}{\mathrm{Charge\mathrm{\left ( \mathit{Q} \right )}}}}$$

The voltage or potential difference between two points in an electric circuit is caused either by an electromotive force (EMF) or by build-up of electric charge. Basically, the voltage can be considered as the electric pressure that forces the electric charge to flow in an electric circuit. The voltage is denoted by letters ‘V or v’ and is measured in volts (V). The electric voltage can be of two types viz. alternating voltage or direct voltage.

What is Current?

The directed flow of electric charge or electrons in a conductor is known as electric current or simply current. The electric current is denoted by ‘I (constant current)’ or ‘i (instantaneous current)’. Mathematically, the electric current can be given by the following expression −

$$\mathrm{\mathit{I}\:=\:\frac{\mathit{Q}}{\mathit{t}} \mathit{\:or\:i} \:=\:\frac{\mathit{dq}}{\mathit{dt}}}$$

Where, Q is the charge in coulomb and t is time in seconds.

Therefore, the electric current can also be defined as the rate of change of electric charge per unit time. The SI unit of electric current is Ampere (A). The electric current can also be of two types viz. direct current (DC) and alternating current (AC).

Difference between Voltage and Current

The key differences between current and voltage are described in the following table −

Parameter	Voltage	Current
Definition	The voltage is defined as the difference in the electric potential between two points in an electric circuit.	The rate of directed flow of electric charge through a conductor is known as electric current or current.
Representation	The voltage between two points denoted by letter ‘V’.	The current flowing through a conductor is denoted by ‘I’.
Unit of measurement	The voltage is measured in Volts (V). The other unit of voltage is ‘Joule per Coulomb’. Where, 1 Joule/Coulomb = 1 Volt	The current is measure in Ampere (A). The other unit of electric current is ‘Coulomb per Second’. Where, 1 Coulomb/second = 1 Ampere
Types	The electric voltage is classified into two types viz. − alternating voltage and direct voltage.	The electric current is also classified into two types, i.e. alternating current and direct current.
Expression	The voltage is given by the expression − $\mathrm{\mathrm{Voltage}\:=\:\frac{\mathrm{Work\: done\mathrm{\left ( \mathit{W} \right )}}}{\mathrm{Charge\mathrm{\left ( \mathit{Q} \right )}}}}$	The electric current is expressed by − $\mathrm{\mathrm{Current}\:=\:\frac{\mathrm{Charge\mathrm{\left ( \mathit{Q} \right )}}}{\mathrm{Time\mathrm{\left ( \mathit{t} \right )}}}}$
In series circuit	The voltage across all the components is different (depending upon the value of element) in a series circuit.	The current flowing through all the elements in a series circuit remains the same.
In parallel circuit	The voltage across all the elements in a parallel circuit remains the same.	The current flowing through all the elements in a parallel circuit is different and depends upon the value of element.
Caused by	The voltage between two points is caused either by build-up of electric charge (as in a capacitor) or by electromotive force (produced by generator).	The current flowing in an electric circuit is caused by the potential difference or voltage between two points in the circuit.
Measuring instrument	A ‘voltmeter’ is used to measure the voltage between two points in an electric circuit.	A measuring instrument called ‘ammeter’ is used to measure the current flowing through a circuit.
Field created	The voltage creates an electrostatic field.	The electric current creates a magnetic field.
Cause & effect	The voltage is the cause of the flow of current.	The current is the effect of the voltage.
Existence	Voltage between two points can exists without current, because the voltage between two points is caused by the EMF of the power source.	Current cannot exists without the voltage.

Conclusion

In this article, we highlighted the key differences between voltage and current. These differences can help an individual to understand the basics of voltage and current better. Both voltage and current are the two fundamental electrical quantities. However, the most significant difference between voltage and current is that the voltage is caused by the EMF that causes the current to flow in a circuit, while the current is the flow of electrons that is caused by the voltage. Therefore, if there is no voltage in a circuit, then no current will flow through the circuit.