Electrical Hunts - Basic Electrical Knowledge
Electrical Voltage
Electrical voltage is defined as electric potential difference between two points of an electric field.
Using water pipe analogy, we can visualize the voltage as height difference that makes the water flow down.
Voltage in series
The total voltage of several voltage sources or voltage drops in series is their sum.
Voltage in parallel
Voltage sources or voltage drops in parallel have equal voltage.
Voltage divider
For electrical circuit with resistors (or other impedance) in series, the voltage drop Vi on resistor Riis:
Kirchhoff's voltage law (KVL)
The sum of voltage drops at a current loop is zero.
DC circuit
Direct current (DC) is generated by a constant voltage source like a battery or DC voltage source.
The voltage drop on a resistor 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
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
Voltage drop
Voltage drop is the drop of electrical potential or potential difference on the load in an electrical circuit.
Voltage Measurement
Electrical voltage is measured with Voltmeter. The Voltmeter is connected in parallel to the measured component or circuit.
The voltmeter has very high resistance, so it almost does not affect the measured circuit.
Voltage by Country
AC voltage supply may vary for each country.
European countries use 230 V while north America countries use 120 V.
| Country | Voltage
[Volts]
| Frequency
[Hertz]
|
|---|---|---|
| Australia | 230 V | 50 Hz |
| Brazil | 110V | 60 Hz |
| Canada | 120V | 60Hz |
| China | 220V | 50Hz |
| France | 230V | 50Hz |
| Germany | 230V | 50Hz |
| India | 230V | 50 Hz |
| Ireland | 230V | 50Hz |
| Israel | 230V | 50Hz |
| Italy | 230V | 50Hz |
| Japan | 100V | 50/60Hz |
| New Zealand | 230V | 50Hz |
| Philippines | 220V | 60Hz |
| Russia | 220V | 50Hz |
| South Africa | 220V | 50Hz |
| Thailand | 220V | 50Hz |
| UK | 230V | 50Hz |
| USA | 120V | 60 Hz |
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