This article describes the important differences between voltage and current. Let us first understand what are voltage and current before understanding the major differences between them.
The two major electrical parameters of any electronic circuit are voltage and current. Voltage is the electrical parameter resulting in the continuous flow of electric charges between two circuit points. This rapid flow of electric charge in the circuit is termed electric current. Georg Simon Ohm put forward Ohm’s law in 1827, stating the direct and proportional relationship between voltage and current in any electronic circuit. Besides the interrelation of voltage and current, some notable differences exist between them.
What is Voltage?
Voltage is defined as the electrical factor of the circuit, which determines the potential difference or voltage drop between any two points of the circuit. In other words, voltage is also called an electromotive force due to the pressure exerted between these two points, which results in the flow of charges across the two points of the circuit.
Voltage is denoted by the symbol ‘V,’ with the unit of measurement being volt (V). The voltage between two points when work is done (W) to move a positively charged proton, denoted by Q, from one point to another in an existing electric field is given by,
Depending on the polarity of the electric voltage between two given points, it can be of the following two types:
- Alternating Voltage – This type of voltage alternates or changes its polarity between positive and negative voltage values.
- Direct Voltage – This type of voltage does not alternate or change its polarity between positive and negative voltage values i.e., it remains constant.
What is Current?
Current is defined as the electric parameter used to measure the rate at which the electric charges flow across any conducting material—in other words, applying the voltage across two given points in an electric circuit results in the continuous motion of electrons across the conducting wire of the circuit.
Electric current is denoted by ‘I,’ which stands for constant or steady current, and ‘i’, which stands for instantaneous current. The unit of measurement for current is Amperes (A). The rate at which the electric charge (Q) across the conductor changes in unit time (t) is given by,
Or, in differential form,
Depending on the direction in which the electric current flows, it can be of two types as follows:
- Direct Current (DC) – When the electric current flows in only one direction in an electric circuit, it is called a direct current.
- Alternating Current (AC) – When the electric current flows in two opposite directions (i.e., positive and negative) in an electric circuit, it is called an alternating current.
Difference between Voltage and Current
The most important differences between the electric voltage and current in an electric circuit are described in the table below.
| Parameter | Voltage | Current |
| Definition | Electric voltage is defined as the potential difference across two points in a circuit. | Current is defined as the continuous rate of flow of electrons in a conductor across two points. |
| Relationship | Voltage is of two types: Direct voltage (DC) and Alternating voltage (AC). | Current is the effect of voltage(Cause). Current cannot flow without Voltage. |
| Types | Current is of two types viz: direct current (DC) and Alternating current (AC). | Current is of two types: direct current (DC) and Alternating current (AC). |
| Symbol | Voltage is represented by the symbol V or v. | Current is represented by the symbol I or i. |
| Unit | The SI unit of Voltage is Volt (V). | The SI unit of current is Ampere (A). |
| Formula | Electric voltage is given by, V= Work done(W)/Charge(Q) | Electric current is given by, I= Charge(Q)/ Time(t) |
| Measuring Tool | A voltmeter is used to measure the electric voltage drop across two given points. | Ammeter is used to measure the current flow through the conductor. |
| Type of Quantity | Voltage is a scalar quantity as it has only magnitude and no direction. | Current is a vector quantity as it has both magnitude and direction. |
| Produced by | Generator, Alternator, and Batteries | Voltage and EMF |
| Existence | Voltage can exist without current, as it is the cause of the flowing charge. Example- Open circuit | The current can flow only in an electric circuit in the presence of voltage. The voltage is the driving force for an electric current. The electric current can not exist without voltage. The closed circuit with voltage causes current to flow in the circuit. |
| Series Combination | The magnitude of the voltage across the electronic and electrical components of a circuit does not remain the same when they are connected in a series combination. | The magnitude of current through the electronic and electrical components of a circuit remains the same when they are connected in a series combination. |
| Parallel Combination | The magnitude of the voltage across the electronic and electrical components in a circuit remains the same when connected in a parallel combination. | The magnitude of current through the electronic and electrical components in a circuit does not remain the same when connected in a parallel combination. |
| Generated by | The flow of electric current in a circuit is generated by the potential difference between the two given points of the circuit. | The flow of electric current in a circuit is generated by the potential difference between the two given points of the circuit. |
| Type of Field Generated | The field generated by voltage is electrostatic force. | The fields generated by the current are the electrical field and the magnetic field. |
| Interrelation | The voltage across any two given points across the conductor causes the flow of electrons in the conductor. | The electric current starts flowing through the conductor due to the voltage applied across two specified points. |
| Polarity/Change in Direction | The direction of electric voltage either alternates (Alternating voltage) or remains constant (Direct voltage). | The direction of electric current either alternates (Alternating current) or remains constant (Direct current). |
Conclusion
This was all about voltage and current. This article discussed the major differences between voltage and current. It also highlights the interrelation of voltage with the current in an electric circuit, which is the most significant difference between the two electrical parameters.
Therefore, the major difference between them is that voltage is generated by the electrical pressure exerted by the electromotive force of the battery source. While the current flows in a circuit because of voltage. Hence, without voltage, there is no current flow in the circuit.