Ohm's Law

on . Posted in Electrical Engineering

Ohm's Law is the relationships between power \((P)\), voltage \((V)\), current \((I)\), and resistance \((R)\).

 ohms pie chart 1

electrical Formulas

Current Power Resistance Voltage
\(\large{ I = \frac{V}{R} }\) \(\large{ P = I^2\;R }\)  \(\large{  R = \frac{V}{I} }\) \(\large{ V = I \; R }\)
\(\large{ I = \sqrt{\frac{P}{R} } }\) \(\large{ P = V\;I }\) \(\large{ R = \frac{P}{I^2} }\) \(\large{ V = \frac{P}{I} }\)
\(\large{ I = \frac{P}{V} }\) \(\large{ P = \frac{V^2}{R} }\) \(\large{ R = \frac{V^2}{I} }\) \(\large{ V = \sqrt{P\;R} }\)


Voltage (Volt)

Volt \(\:(V)\:\) or \(\:(E)\:\) is a unit of electrical pressure. One volt is the amount of pressure that will cause one ampere of current in one ohm of resistance. Different voltages that are typically used in the oilfield in the USA are 480V, 4,160V and 12kV (Kilo Volt)


Current (Amp)

Current \(\:(I)\:\) is the rate of flow of electricity passing through a circuit per unit of time., measured in amperes.

Amp is a unit of current. One ampere (amp) is the current flowing through one ohm of resistance at one volt potential.


Power (Watt)

Power \(\:(P)\:\) is the rate of doing work and is measured by the amount of foot pounds of work done in a particular unit of time. A horsepower is a measure of power.


Resistance (Ohm)

Resistance \(\:(R)\:\) is the ability to resist or prevent the flow of current. In order to overcome the resistance and get the current to flow a higher voltage will be required. Resistance is measured in Ohms, represented by \(R\) and has a symbols \(\Omega\).            

Ohm is a unit of resistance. A constant current of one ampere produces a force of one volt.


electrical symbols

Quantity Symbol Unit Formula
Capacitance \(C\) Farad \(C= \frac{Q}{V}\)
Charge \(Q\) Coulomb \(Q= I \; t\)
Conductance \(G\) Siemen \(G=\frac{P}{V^2}\)
Current \(I\) Ampere \(I= \frac{V}{R}\)
Frequency \(Hz\) Hertz \(f=1 + T\)
Impedance \(Z\) Ohm \(Z=\sqrt{R^2 + \left( X_L - X_C \right)^2 } \)
Inductance \(L\;\) or \(\;H\) Henry \( L = \mu \; n^2 \;\frac{A}{l} \) 
Power \(P\) Watt \(P=V \; I\)
Resistance \(R\;\) or \(\;\Omega\) Ohm \(R=\frac{V}{I}\)
Voltage \(V\;\) or \(\;E\) Volt \(V=I \; R\)


electrical Units (Multipliers and Submultipliers)

Prefix Symbol Multiplier Power of Ten
yotto Y \( 1,000,000,000,000,000,000,000,000\) \(10^{24}\)
zetta Z \( 1,000,000,000,000,000,000,000\) \(10^{21}\)
exa E \( 1,000,000,000,000,000,000\) \(10^{18}\)
peta P \( 1,000,000,000,000,000\) \(10^{15}\)
tera T \( 1,000,000,000,000\) \(10^{12}\)
giga G \( 1,000,000,000\) \(10^{9}\)
mega M \( 1,000,000\) \(10^{6}\)
kilo k \( 1,000\) \(10^{3}\)
hecto h \(100\) \(10^{2}\)
deca da \(10\) \(10^{1}\)
none none \( 1\) \(10^{0}\)
deci d \({\large\frac{1}{10}}\) \(10^{-1}\)
centi c \({\large\frac{1}{100}}\) \(10^{-2}\) 
milli m \({\large\frac{1}{1,000}}\) \(10^{-3}\) 
micro \(\mu\) \({\large\frac{1}{1,000,000}}\) \(10^{-6}\) 
nano n \({\large\frac{1}{1,000,000,000}}\) \(10^{-9}\) 
pico p \({\large\frac{1}{1,000,000,000,000}}\) \(10^{-12}\)
femto f \({\large\frac{1}{1,000,000,000,000,000}}\)  \(10^{-15}\)
atto a \({\large\frac{1}{1,000,000,000,000,000,000}}\) \(10^{-18}\) 
zepto z \({\large\frac{1}{1,000,000,000,000,000,000,000}}\) \(10^{-21}\) 
yocto y \({\large\frac{1}{1,000,000,000,000,000,000,000,000}}\)  \(10^{-24}\)


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Tags: Electrical Equations Cathodic Protection Equations Laws of Physics