Voltage (V) electrical unit
What is a Voltage?
Electrical Voltage is defined as the electric potential difference between 2-points of an electric field.
Using the water pipe analogy, we can visualize the voltage as a height difference that makes the water flow down.
Calculation to Electric Field formula:
V = φ2 – φ1
V = is the voltage between point 2 and 1 in volts (V).
φ2 = is the electric potential at point-2 in volts (V).
φ1 = is the electric potential at point-1 in volts (V).
Volt definition
Volt is the electrical unit of voltage or potential difference (symbol: V).
1 Volt is defined as energy consumption of 1 joule per electric charge of 1 coulomb.
1V = 1J/C
1 volt is equal to a current of 1 amp times the resistance of 1 ohm:
1V = 1A × 1Ω
Alessandro Volta
A Volt unit is named after Alessandro Volta, an Italian physicist who invented an electric battery.
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Electric Voltage Calculation
In an electrical circuit, the electrical voltage (V) in volts (V) is equal to the energy consumption (E) in Joules (J).
divided by the electric charge Q in coulombs (C).
V = is the voltage measured in volts (V)
E = is the energy measured in joules (J)
Q = is the electric charge measured in coulombs (C).
Volt subunits and conversion table
| name | symbol | conversion | example |
|---|---|---|---|
| microvolt | μV | 1μV = 10-6V | V = 30μV |
| millivolt | mV | 1mV = 10-3V | V = 5mV |
| volt | V | - |
V = 10V |
| kilovolt | kV | 1kV = 103V | V = 2kV |
| megavolt | MV | 1MV = 106V | V = 5MV |
Voltage in series Circuit Connection
The total voltage of several voltage sources Supply or voltage drops in series is their sum.
VT = V1 + V2 + V3 +…
VT = the equivalent voltage source or voltage drop in volts (V).
V1 = voltage source or voltage drop in volts (V).
V2 = voltage source or voltage drop in volts (V).
V3 = voltage source or voltage drop in volts (V).
Voltage in Parallel Circuit Connection
The total voltage of several voltage sources Supply or voltage in Parallel I have equal Voltage.
VT = V1 = V2 = V3 =…
VT = the equivalent voltage source or voltage Same or equal in volts (V).
V1 = voltage source or voltage equal in volts (V).
V2 = voltage source or voltage equal in volts (V).
V3 = voltage source or voltage equal in volts (V).
Voltage Divider Circuit Connection for DC Circuit
For an Electrical circuit with resistors (or other impedance) in series, the voltage drop Vi on resistor Ri is:
For a DC circuit with a constant voltage source VT and resistors in series, the voltage drop Vi in resistor RI is given by the formula:
Vi – voltage drop in resistor Ri in volts [V].
VT – the equivalent voltage source or voltage drop in volts [V].
Ri – resistance of resistor Ri in ohms [Ω].
R1 – resistance of resistor R1 in ohms [Ω].
R2 – resistance of resistor R2 in ohms [Ω].
R3 – resistance of resistor R3 in ohms [Ω].
Voltage Divider Circuit Connection for AC Circuit
For an AC circuit with voltage source VT and loads in series, the voltage drop Vi in load Zi is given by the formula:
Vi – voltage drop in load Zi in volts [V].
VT – the equivalent voltage source or voltage drop in volts [V].
Zi – impedance of load Zi in ohms [Ω].
Z1 – impedance of load Z1 in ohms [Ω].
Z2 – impedance of load Z2 in ohms [Ω].
Z3 – impedance of load Z3 in ohms [Ω].
Kirchhoff’s voltage law (KVL) Circuit Connection
The sum of the voltage drops at a current loop is zero.
∑ Vk = 0
DC Circuit Connection
Direct current Line (DC) is generated by a constant voltage source like a battery (12V) or DC voltage source.
The voltage drop on a resistor (R) can be calculated from the resistor’s resistance and the resistor’s current, using Ohm’s law:
Voltage calculation with Ohm’s law
VR = IR × R
VR = voltage drop on the resistor measured in volts (V).
IR = current flow through the resistor measured in amperes (A).
R = resistance of the resistor measured in ohms (Ω)
AC Circuit Connection
An alternating current is generated by a sinusoidal voltage source.
Ohm’s law
VZ = IZ × Z
VZ = voltage drop on the load measured in volts (V)
IZ – current flow through the load measured in amperes (A)
Z – impedance of the load measured in ohms (Ω)
Momentary voltage
v(t) = Vmax × sin(ωt+θ)
v(t) = voltage at time t, measured in volts (V).
Vmax = maximal voltage (= amplitude of sine), measured in volts (V).
ω = angular frequency measured in radians per second (rad/s).
t = time, measured in seconds (s).
θ = phase of sine wave in radians (rad).
RMS (effective) voltage
Vrms = Veff = Vmax / √2 ≈ 0.707 Vmax
Vrms = RMS voltage, measured in volts (V).
Vmax = maximal voltage (=amplitude of sine), measured in volts (V).
Peak-to-peak voltage
Vp-p = 2Vmax
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Line Voltage by Country
AC voltage supply may vary for each country.
| Country | Voltage (V) | Frequency (Hz) |
|---|---|---|
| China | 220V | 50Hz |
| Philippines | 220V | 50Hz |
| Russia | 220V | 50Hz |
| South Africa | 220V | 50Hz |
| Thailand | 220V | 50Hz |
| France | 230V | 50Hz |
| Germany | 230V | 50Hz |
| India | 230V | 50Hz |
| Ireland | 230V | 50Hz |
| Israel | 230V | 50Hz |
| Italy | 230V | 50Hz |
| New Zealand | 230V | 50Hz |
| UK | 230V | 50Hz |
| Japan | 100V | 50/60Hz |
| Brazil | 110V | 60Hz |
| USA | 120V | 60Hz |
| Canada | 120V | 60Hz |
Volts to watts conversion
The power in watts (W) is equal to the voltage in volts (V) times the current in amps (A):
watts (W) = volts (V) × amps (A)
Volts to joules conversion
The energy in joules (J) is equal to the voltage in volts (V) times the electric charge in coulombs (C):
joules (J) = volts (V) × coulombs (C)
Volts to amps conversion
The current in amps (A) is equal to the voltage in volts (V) divided by the resistance in ohms (Ω):
amps (A) = volts (V) / ohms(Ω)
The current in amps (A) is equal to the power in watts (W) divided by the voltage in volts (V):
amps (A) = watts (W) / volts (V)
Volts to electron-volts conversion
The energy in electronvolts (eV) is equal to the potential difference or voltage in volts (V) times the electric charge in electron charges (e):
electronvolts (eV) = volts (V) × electron-charge (e)
electronvolts (eV) = volts (V) × 1.602176e-19 coulombs (C)
Voltage Drop Definition
A Voltage drop is the drop of electrical potential or potential difference in the load in an electrical circuit diagram.
Voltage Measurement Definition
Electrical voltage is measured with a Voltmeter. The Voltmeter is connected in parallel to the measured component or circuit testing. The voltmeter has very high resistance, so it almost does not affect the measured circuit.
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