|The nominal impedance Z = 4, 8, and 16 ohms (loudspeakers) is often assumed as resistance R.
Ohm's law equation (formula): V = I × R and the power law equation (formula): P = I × V.
P = power, I or J = Latin: influare, international ampere, or intensity and R = resistance.
V = voltage, electric potential difference Δ V or E = electro motive force (EMF = voltage).
|Enter any two of the following values and click the calculation button.
The missing values will be calculated. Enter only two values.
|V comes from "voltage" and E from "electromotive force". E means also energy, so V is chosen. Energy = voltage × charge. E = V × Q. Some like better to stick to E instead to V, so do it.|
|Voltage V = I × R = P / I = √(P × R) in volts V Current I = V / R = P / V = √(P / R) in amperes A
Resistance R = V / I = V2 / P = P / I2 in ohms Ω Power P = V × I = R × I2 = V2 / R in watts W
| The Big Power Formulas
Electrical and mechanical power calculation
Power is like all energy sizes
primarily a calculated value.
Tip: The electric power triangle (power formula)
The magic triangle can be used to calculate all formulas of the "electric power law". You hide with
a finger the value to be calculated. The other two values show then how to do the calculation.
Please enter two values, the third value will be calculated.
Calculations: Ohm's law - Ohm's magic triangle
Measurement of input impedance and output impedance
ALTERNATING CURRENT (AC) ~
Vl = line voltage (volts), Vp = phase voltage (volts), Il = line current (amps), Ip = phase current (amps)
Z = impedance (ohms), P = power (watts), φ = power factor angle, VAR = volt-amperes (reactive)
|Current (single phase): I = P / Vp×cos φ||Current (3 phases): I = P / √3 Vl×cos φ or I = P / 3 Vp×cos φ|
|Power (single phase): P = Vp×Ip×cos φ||Power (3 phases): P = √3 Vl×Il×cos φ or P = √3 Vp×Ip×cos φ|
|frequency f||hertz (Hz)||1/s|
|force F||newton (N)||kg·m/s²|
|pressure p||pascal (Pa) = N/m²||kg/m·s²|
|energy E||work joule (J) = N·m||kg·m²/s²|
|power P||watt (W) = J/s||kg·m²/s³|
|electric charge Q||coulomb (C) = A·s||A·s|
|voltage V||volt (V)= W/A||kg·m²/A·s³|
|capacitance C||farad (F)= C/V = A·s/V = s/Ω||A²·s4/kg·m²|
|inductance L||henry (H) = Wb/A = V·s/A||kg·m²/A²·s²|
|resistance R||ohm (Ω) = V/A||kg·m²A²·s³|
|conductance G||siemens (S) = A/V||A²·s³/kg·m²|
|magnetic flux Φ||weber (Wb) = V·s||kg·m²/A·s²|
|flux density F||tesla (T) = Wb/m² = V·s/m²||kg/A·s²|
|The flow of electric charge Q is referred to as an electrical current I. The amount of charge per unit time
is the change in electrical current. A current flows at a constant value I. during the time t, it transports the
charge Q = I × t. For a temporally constant power, the relationship between the charge and current:
I = Q / t or Q = I × t. Through this relationship, the basic units of amps and second the Coulomb in International System of Units is set. The Coulomb unit can be represented as 1 C = 1 A × s.
In acoustics we have an "Acoustic equivalent for ohm's law"
Relationships of acoustic sizes associated with plane progressive sound waves
Conversions of many units, like power and energy
prefixes | length | area | volume | weight | pressure | temperature | time | energy | power | density | velocity | acceleration | force
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