How do I calculate electrical loads

Electrical current, electrical power
and electrical voltage
electricity and electric charge
The most common general formulas in electrical engineering
Formulas and Calculations 
context the physical and electrical quantities (Parameters)
Electric voltageU,AmperageI.,resistanceR., ImpedanceZ, powerP
voltin V,ampin A,resistance and Impedance in ohm Ω andwatt in W
In physics we speak of electrical voltage and electrical current as the strength of the current.
How do I calculate the voltage? Avoid the weird wrong word Voltage,
that tour operators and lawyers like to use and replace with one of the following
Words: electrical voltage, operating voltage or mains voltage. Practitioners rarely speak of
the Potential difference, when simply electrical voltage is meant.
Even if the last name of the namesake "Ampère" is written with accent grave,
The SI unit in the German and English-speaking countries is written without an accent, ie "Ampere".
For the resistance R. often becomes the nominal impedance Z = 4, 8 and 16 ohms assumed (loudspeaker)
The impedance is the alternating current resistance, which consists of the components capacitor, coil and
ohmic resistance is formed and its value and phase position changes with frequency.
Ohm's law U = R · I. or Ohm's law including power P = U · I; P = power.
I. = international ampere, intensity or Latin influare (to flow in), E. = electromotive force (EMF)
and R. = resistance. U comes from the Latin urgere (urge, drive, press). U is supposed
also mean "difference" because of the potential difference as a difference or also as a voltage drop.
If you don't like the vile word voltage, you can also use voltage in a very elegant way (electrical)
Call the potential difference. The letter I. can come from "International Ampere", but also from lat. influare
(flow in) come and R. of resistance or of resistare (to resist).
Formulas: URI and PUI.
Please enter two values - the other two values ​​are calculated.

Basics of electrical laws
Electronics formula collection
 The formula wheel ▼  Important formulas  
& # 160 of electrical engineering for electronics
Electrical formulas in circle representation (diagram)
The formula wheel of electrical engineering
In English is U not known for tension. There you know "voltage" = V or E. by "electro motive force"
Energy = tension · Charge. E. = U · Q. For the resistance R. is also the impedance Z to take.
The 12 most important formulas:
tension U = R.·I. = P / I. = √(P·R.) in volts V amperage I. = U / R. = P / U = √(P / R.) in ampere A
resistance R. = U / I. = P / I.2 = U2 / Pin Ohm Ω power P = U·I. = R.·I.2 = U2/ R. in watt W
See also: The formula wheel of acoustics (audio)

The big ones Performance formulas   
or, more contemporary, "The Mega Power Formulas"
- Electrical and mechanical power calculation (strength)

 Performance formula 1 - Electric power equation: powerP = U · I. = R. · I.2 = U2R.
here is performance P in watts, voltage U in volts and amperage I. in amps.
With alternating current, the power factor cos φ, i.e. the power factor angle φ
(Phase angle) between voltage and current must be observed.
Electric energy is E. = P·t - measured in watt hours or in kWh. 1J = 1N·m = 1W·s
 Performance formula 2 - Mechanical power equation: power P = Δ E / Δ there is
 Δ W = work done accordingly Δ E = energy expended.
power P in watts. power P = Work / time (W.t).
 energyE. in joules and time t in seconds. 1 W = 1 joule / second.
Power = force times distance (deflection) through time, that is P = F · s / t or in other words:
Power = power times speed, so P = F · v.
The powerful sound you are looking for cannot be found in these formulas. Watch your ears!
The eardrums of our ears and also microphones really only react to thatSound pressure
and are thereby effectively moved. That doesn't affect the intensity, the performance or
even the energy. Anyone who is involved in creative sound recording in sound engineering is doing well
remember to care less about the root cause than to worry about intensity, power and energy, but rather the
pay more attention to that effect of sound pressure p and level(Sound pressure level) on the ears
and the microphones, as well as the audio voltage corresponding to this all U ~ p; please refer:
 Sound pressure and sound power - effect and cause
Loud loudspeakers - they like Boxing - should be called a lot of "power",
thus perform; better see the significant one Efficiency the speaker.
This includes the typical question:
 How many decibels are actually twice, three times or four times as loud?
In reality, there is no effective value (RMS) for power as an energy quantity.
"RMS performance" is not intended to indicate in a completely correct manner that this performance
was calculated from the product of rms voltage and rms current. Just read:
 Why there are no 'RMS Watts' or 'Watt RMS' - and never have been.
"RMS" Power is a pretty silly term, but one that is popular among audio folks.
Power is the amount of energy that is converted in a certain time unit.
If you want more power, you have to pay more all the time.
André-Marie Ampère was a French physicist and mathematician.
The SI unit of measurement of electrical current in amp, was named after him.
Alessandro Giuseppe Antonio Anastasio Volta was an Italian physicist.
The SI unit of measurement of electrical voltage in volt, was named after him.
Georg Simon Ohm was a German physicist and mathematician.
The SI unit of measurement of electrical resistance in ohm, was named after him.
James Watt was a Scottish inventor and mechanical engineer.
The SI unit of measurement of electrical power in watt, was named after him.
Power, like all energy quantities, is predominantly a calculated quantity.
The word "power amplifier" is incorrect - especially in audio engineering.
Voltage and current can be amplified.
The term "power amplifier" is strange, but it means
that an amplifier should drive a load - like a loudspeaker.
We call the product of the current and voltage gain simply
"Power Boost".


Apparent power =
√ (active line2 +
Reactive power2)
Courtesy of Brian Willis and Causeway Art Studio

Tip: The triangle of electrical voltage U = R. · I. (Ohm's Law URI)

You're welcome two Enter values, the third value will be calculated.

Tip: The triangle of electrical power P = U · I. (PUI benefit law)

You're welcome two Enter values, the third value will be calculated.

A "magic triangle" can be used to calculate all formulas quite easily.
The value to be calculated is covered. The result is calculated with the other two values.

Calculations: Ohm's law - The magic triangle


Ul = Mains voltage (volts), Up = Phase voltage (volts), I.l = Mains current (amps), I.p = Phase amperage (amperes)
Z = Impedance (ohms), P = Power (watt) φ = Power factor (angle), VAR = volt-ampere (reactive)

Amperage (single phase): I. = P / U· cos φ  Current strength (3 phases): I. = P / √3 Ul· cos φ or I. = P / 3 U· cos φ 
Performance (single phase): P = Up·I.p · cos φ  Performance (3 phases): P = √3 Ul·I.l· cos φ or P = √ 3 Up·I.p · cos φ 
Power factor PF = cos φ = R / (R2 + X2)1/2, φ = Power factor angle. When direct current is PF = 1.

The term cos φ is called power factor, active factor or displacement factor. This is
the quotient of active and apparent power (cos φ = P / S) or the cosine of the phase shift.
The apparent power S. is calculated according to Pythagoras from the active power P and reactive power Q.    S. = √(P2 + Q2)

DC power formulas
Stress calculation U in (V) from amperage I. in (A) and resistance R. in (Ω):
U(V) = I.(A) × R.(Ω)
The performance calculation P in (W) from voltage U in volts (V) and amperage I. in (A):
P(W) = U(V) ×I.(A) = U2(V) / R.(Ω) = I.2(A) × R.(Ω)
AC power formulas
The voltage U in volts (V) is equal to the current strength I. in amps (A) times the impedance Z in Ohm (Ω):
U(V) = I.(A) × Z(Ω) = (| I. | × | Z |) and (θI. + θZ)
The apparent power S. in volt-amperes (VA) is equal to the voltage U in volts (V) times the current I.
in ampere (A):
S.(VA) = U(V) × I.(A) = (| U | × | I. |) and (θVθI.)
The real powerP in watts (W) is equal to the voltage U in volts (V) times the current I. in amps
(A) times the power factor (cos φ):
P(W) = U(V) × I.(A) × cos φ
The reactive power Q in volts-amperes reactive (VAR) is equal to the voltage U in volts (V) times the
Amperage I. in amperes (A) times the sine of the complex power phase angle (φ):
Q(VAR) = V(V) × I.(A) × sin φ
The power factor (FP) is equal to the absolute value of the cosine of the complex
Power phase angle (φ):
PF = | cos φ |

Electrical dimension definitions
frequency fHertz (Hz)1 / s
force F.Newton (N)kg·m / s²
print pPascal (Pa) = N / m²kg / m·
energy E.Work Joule (J) = N·mkg·m² / s²
power PWatt (W) = J / skg·m² / s³
Electric charge QCoulomb (C) = A·sA.·s
tension UVolts (V) = W / Akg·m² / A·
electricity I.Amps (A) = Q / sA.
capacity C.Farad (F) = C / V = ​​A·s / V = ​​s / Ω·s4/ kg·
Inductance L.Henry (H) = Wb / A = V·s / Akg·m² / A²·
resistance R.Ohm (Ω) = V / Akg·m²A²·
conductivity GSiemens (S) = A / V·s³ / kg·
Magnetic flux ΦWeber (Wb) = V·skg·m² / A·
Flux density B.Tesla (T) = Wb / m² = V·s / m²kg / A·

The flow of electrical charge Q is called electric current I. designated. The change in the amount of charge per
The unit of time is the electrical current strength. A current flows with constant strength I. During the time tso he transports
the charge Q = I · t. For a current that is constant over time, the relationship between charge and current is: I = Q / t
or Q = I · t. Because of this relationship of the base units amps and seconds, the coulomb is in internationals
System of units specified. The unit Coulomb can be expressed as 1 C = 1 A. · s represent.
charge Q, (Unit in ampere-hours Ah), discharge current I., (Unit in ampere A), time t, (Unit in hours h).

The acoustic equivalence to Ohm's law (calculator)

This applies to acoustics acoustic equivalent to Ohm's law

Relationship of the acoustic quantities in the case of flat, progressing sound waves

Conversions of other units, such as power and energy

Prefixes | Length | Area | Volume | Weight | Pressure | Temperature | Time | energy | power | Density | Speed ​​| Acceleration | force

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