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## 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.

### 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)

v(t) = voltage at time t, measured in volts (V).

Vmax = maximal voltage (= amplitude of sine), measured in volts (V).

t = time, measured in seconds (s).

RMS (effective) voltage

VrmsVeff =  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

### 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

### 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.