Ohm's law calculation calculator calculate ohms formulas - voltage current resistance formula - magic triangle equation tip online voltage volts resitor resistance amps amperes audio engineering E V I R calc conductivity resistivity

● Ohm's law - calculator and formulas ●

Resistance (ohms), current (amps), and voltage (volts)

Ohm's Law is the linear proportionality between current and voltage that occurs for most conductors
of electricity. A graph of voltage against current is a straight line. The gradient is the resistance.

Practitioners rarely speak of potential difference, when electrical voltage (drop) is meant.

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V = R × I I = V / R R = V / I

The formulas of Ohm's Law

Ohm's Law can be rewritten in three ways for calculating current, resistance, and voltage.
If a current I should flow through a resistor R, the voltage V can be calculated.
V = R × I

If there is a voltage V across a resistor R, a current I flows through it. I can be calculated.
I = V / R

If a current I flows through a resistor, and there is a voltage V across the resistor R can be calculated.
R = V / I

Name	Formula sign	Unit	Symbol
voltage	V or E	volt	V
current	I	ampere (amp)	A
resistance	R	ohm	Ω
power	P	watt	W

Tip: Ohm's magic triangle

The magic V I R triangle can be used to calculate all formulations of ohm's law.
Use a finger to hide the value to be calculated. The other two values then show
how to do the calculation.

The symbol I or J = Latin: influare, international ampere, and R = resistance. V = voltage,
electric potential difference, also called voltage drop, or E = electro motive force (EMF = voltage).

If you need the unit of power P = V × I look for the
Big Power Formulas:
Calculations: power, voltage, current, resistance, and power

Some are of the opinion that Georg Simon Ohm calculated the "specific resistance".
Therefore they believe that only this can be the true ohm's law.

	Value of the Resistance

R	= Resistance	Ω
ρ	= Electrical resistivity	Ω·m
l	= Cable length	m
A	= Cross-sectional area	m²

Electrical conductivity (conductance) σ (sigma) = 1/ρ
Specific electrical resistance (resistivity) ρ (rho) = 1/σ

Electrical conductors	Electrical conductivity Electrical conductance	Electrical resistivity Specific resistance
silver	σ = 62	ρ = 0.0161
copper	σ = 58	ρ = 0.0172
aluminium	σ = 36	ρ = 0.0277

To use the calculator, simply enter a value.
Calculator works in both directions of the ↔ sign.

The value of the electrical conductivity (conductance) and the specific electrical resistance
(resistivity) is a temperature dependent material constant. Mostly it is given at 20 or 25°C.
Resistance R = ρ × (l / A) or R = l / (σ × A)

For all conductors the specific resistivity changes with the temperature. In a limited
temperature range it is approximately linear:

where α is the temperature coefficient, T is the temperature and T₀ is any temperature,
such as T₀ = 293.15 K = 20°C at which the electrical resistivity ρ (T₀) is known.

Cross-sectional area - cross section - slice plane

Now there is the question:
How can you calculate the cross sectional area (slice plane) A
from the wire diameter d and vice versa?

Calculation of the cross section A (slice plane) from diameter d:

r = radius of the wire
d = diameter of the wire

Calculation diameter d from cross section A (slice plane):
Formel Berechnung Durchmesser aus Querschnitt
Cross section A of the wire in mm² inserted in this formula gives the diameter d in mm.

Calculation − Round cables and wires:
• Diameter to cross section and vice versa •

Electrical voltage V = I × R (Ohm's law)

Electrical voltage = amperage × resistance

Please enter two values, the third value will be calculated.

Electric power P = V × I (Power law)

Electric power = voltage × amperage

Please enter two values, the third value will be calculated.

Ohm's law. V = I × R, where V is the potential across a circuit element, I is the current
through it, and R is its resistance. This is not a generally applicable definition of
resistance. It is only applicable to ohmic resistors, those whose resistance R is
constant over the range of interest and V obeys a strictly linear relation to I. Materials
are said to be ohmic when V depends linearly on R. Metals are ohmic so long as one
holds their temperature constant. But changing the temperature of a metal changes R
slightly. When the current changes rapidly, as when turning on a light, or when using AC
sources, slightly non-linear and non-ohmic behavior can be observed. For non-ohmic
resistors, R is current-dependent and the definition R = dV/dI is far more useful. This is
sometimes called the dynamic resistance. Solid state devices such as thermistors are
non-ohmic and non-linear. A thermistor's resistance decreases as it warms up, so its
dynamic resistance is negative. Tunnel diodes and some electrochemical processes
have a complicated I to V curve with a negative resistance region of operation. The
dependence of resistance on current is partly due to the change in the device's
temperature with increasing current, but other subtle processes also contribute to
change in resistance in solid state devices.

Calculation: Parallel Resistance (Resistor) Calculator

Color Code Calculator for Resistors

In acoustics we use ohm's law as acoustic equivalent

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Electrical conductivity σ: S · m / mm²	↔	Specific elec. resistance ρ: Ohm ∙ mm² / m
σ = 1 / ρ		ρ = 1 / σ