52 ϟ
52 calculators. Clear formulas and interactive charts.
Ohm's law
U = R × I · P = U × I
↗△Power triangle
S = P / cos φ · Q = P × tan φ
↗≋Series and parallel resistance
Rserie = ΣR · 1/Rparallell = Σ(1/R)
↗↧Voltage divider
Uut = Uin × R₂ / (R₁ + R₂)
↗⑂Current divider
I₁ = I × R₂/(R₁ + R₂)
↗3φThree-phase power
I = P / (√3 × U × cos φ)
↗∿RLC impedance
Z = √(R² + (Xᴸ − Xᶜ)²)
↗⊣Capacitor
Xᶜ = 1/(2πfC) · E = ½CU²
↗HzFrequency and period
T = 1/f · ω = 2πf
↗φPower factor correction
Qc = P × (tan φ₁ − tan φ₂)
↗ΔUVoltage drop
ΔU ≈ k × I × R × cos φ
↗ρCable resistance
R = ρ₂₀ × [1 + α(T − 20)] × L/A
↗IκShort-circuit current
Ik = c × U₀ / √(R² + X²)
↗ALoad current
I = P / (k × U × cos φ)
↗mm²Cable data check
Iz = Iztabell × kt × kg
↗MMotor power
I = Pmek / (η × √3 × U × cos φ)
↗rpmSpeed and slip
ns = 120f/p · n = ns(1 − s)
↗kWhEnergy cost
E = P × t · Kostnad = E × pris
↗N₁Transformer
U₁/U₂ = N₁/N₂ = I₂/I₁
↗▰Battery runtime
t ≈ U × Ah × DoD × η / P
↗ΣIKirchhoff: two nodes
ΣIin = ΣIut · IAB = IA + IB · I₂ = IAB + IC
↗⑂Kirchhoff: branch currents
I = I₁ + I₂ · I₁ = I − I₂
↗ΣUKirchhoff's voltage law
U − U₁ − U₂ = 0 · U₂ = U − U₁
↗2RTwo resistors: voltage, current, power
Serie: R = R₁ + R₂ · Parallell: R = R₁R₂/(R₁ + R₂) · P = UI = I²R = U²/R
↗R∥Mixed resistor circuit
Rp = R₁R₂/(R₁ + R₂) · Rtot = Rs + Rp · I = U/Rtot · Up = I × Rp · I₁ = Up/R₁ · P = I²R
↗ESource internal resistance
Ib = E/(Ri + Rb) · Ub = E − IbRi = IbRb
↗RLRL series circuit
XL = 2πfL · Z = √(R² + XL²) · I = U/Z · φ = arctan(XL/R)
↗UIAC power from voltage and current
S = kUI · P = S cos φ · Q = S sin φ · k = 1 eller √3
↗RCRC charging
Uc = U(1 − exp(−t/RC))
↗RCRC discharging
Uc = U₀ exp(−t/RC)
↗RLRL current transient
I = (U/R)(1 − exp(−tR/L))
↗LCLC resonance
f₀ = 1/(2π√(LC))
↗LPRC low-pass filter
fc = 1/(2πRC) · |H| = 1/√(1 + (2πfRC)²)
↗HPRC high-pass filter
fc = 1/(2πRC) · |H| = x/√(1+x²), x = 2πfRC
↗√2RMS and peak voltage
Û = √2 Urms · Upp = 2Û
↗XLInductive reactance
XL = 2πfL
↗JInductor energy
E = ½LI²
↗C∥Parallel capacitors
C = C₁ + C₂ + C₃
↗CsSeries capacitors
1/C = 1/C₁ + 1/C₂ + 1/C₃
↗LEDLED series resistor
R = (U − Uf)/I · PR = (U − Uf)I
↗QJoule heating
Q = I²Rt
↗I²RConductor power loss
Pförlust = I²R
↗ρResistivity
ρ = RA/L
↗YΔStar–delta resistance
RΔ = 3RY
↗NmMotor torque
M = P/ω · ω = 2πn/60
↗sSlip from rotor speed
s = (ns − n)/ns · fr = |s|f
↗ηEfficiency
η = Put/Pin
↗EVEV charging time
t = C(SOCslut − SOCstart)/(Pη)
↗BsBatteries in series
Userie = nU · Ahserie = Ah
↗B∥Batteries in parallel
Uparallell = U · Ahparallell = nAh
↗dBVoltage gain in dB
G = 20 log₁₀(Uut/Uin)
↗dBPower gain in dB
G = 10 log₁₀(Put/Pin)
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