Electrical voltage, also known as potential difference, is the energy transfer between two points in an electrical circuit . This difference drives the electric current through the conductor and determines the amount of work done in the system.
Voltage Definition and Basics
Voltage represents the work done in moving 1 coulomb of charge from one point in the circuit to another.
U = W / Q
U: voltage (volts, V)
W: work (joules, J)
Q: charge (coulomb, C)
Definition of a volt: One volt (1 V) of voltage is present when 1 coulomb of charge gains or loses 1 joule of energy while passing between two points.
Voltage types:
- Direct current (DC): The voltage is constant, its direction and magnitude do not change. Example: Battery-type energy sources (e.g. 1.5 V pencil battery).
- Alternating voltage (AC): Voltage that changes periodically, both in magnitude and direction. Example: Household electrical network (230 V, 50 Hz in Hungary).
Voltage and electric current
Voltage is the “driving force” of electric current, which moves the current through the conductor. The relationship can be described by Ohm’s law:
U = I × R
U: voltage (volts, V)
I: current (amperes, A)
R: resistance (ohms, Ω)
Example: A current of 2 A flows in a circuit if the resistance is 5 Ω:
U = 2 × 5 = 10 V
Voltage measurement
Voltage measuring devices are used to measure electrical voltage, such as:
- Digital multimeters: They offer accurate and wide-ranging measurements.
- Analog voltage meters: They have a clear display and are suitable for simpler measurements.
Practical examples
Direct current (DC):
- Electric cars: Batteries typically operate at 400-800 V DC.
- Electronic devices: Many devices, such as laptops and mobile phones, require 5V, 9V or 12V.
Alternating voltage (AC):
- Household network: In Hungary, the standard alternating voltage is 230 V, with a frequency of 50 Hz.
- Industrial systems: Industrial equipment often uses 400V three-phase alternating voltage.
The role of voltage in energy transfer
Energy-efficient transportation: During long-distance transportation, high voltages (e.g. 110 kV or higher) are used to minimize energy losses. Transformers reduce the voltage to a safe level near energy consumers.
Safety: Lower voltages are used in everyday equipment (e.g. 12V LED lights) to minimize the risk of electric shock.
Historical background of tension
Alessandro Volta (1745–1827): The unit of measurement for electrical voltage, the volt, is named after the Italian physicist Volta, who invented the first electrochemical cell, the voltaic pile.
Ohm's Law (Georg Simon Ohm): Describes the relationship between electrical resistance, current, and voltage, which is fundamental to modern electricity.
Voltage and power relationship
Electrical power (P) can be calculated using voltage, current, and resistance:
P = U × I
P = I² × R
P = U² / R
Example:
An electrical device is connected to a 230 V network and draws 2 A of current:
P = 230 × 2 = 460 W
This device operates at a power of 460 watts.
Voltage and safety
Low voltage: Safer and less risk of electric shock (e.g. 12V systems).
High voltage: It carries greater risk and therefore requires special protection and insulation.
Grounding: Grounding is an important protective mechanism that conducts away excess current and reduces the risk of electric shock.
Summary
Electrical voltage, a measure of potential difference, is a fundamental concept in the operation of electrical circuits. Voltage determines the efficiency and direction of energy transfer, playing a key role in modern technologies, power supply, and the operation of everyday devices. Proper measurement, regulation, and application of voltage are essential for safe and efficient electrical systems.