Ohm's Law

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

 

OHM'S LAW PIE CHART

 

 

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)

 

Voltage formulas

\(\large{ Volts = \sqrt{Watts \; Ohms} = V = \sqrt{P \; R} }\)
\(\large{ Volts = \frac{Watts}{Amps} = V = \frac{P}{I} }\)
\(\large{ Volts = Amps \; Ohms = V = I \; R }\)

 

Current (Amp)

Current \(\:(I)\:\) is the rate of flow of electricity in a circuit, 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.

 

Current formulas

\(\large{ Amps = \frac{Volts}{Ohms} = I = \frac{V}{R} }\)
\(\large{ Amps = \frac{Watts}{Volts} = I = \frac{P}{V} }\)
\(\large{ Amps = \sqrt{\frac{Watts}{Ohms}} = I = \sqrt{\frac{P}{R}} }\)

 

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.

 

Power formulas

\(\large{ Watts = \frac{Volts^2}{Ohms} = P = \frac{V^2}{R} }\)
\(\large{ Watts = Volts^2 \; Ohms = P = V^2 \; R }\)
\(\large{ Watts = Volts \; Amps = P = V \; I }\)

 

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.

 

Resistance formulas

\(\large{ Ohms = \frac{Volts}{Amps} = R = \frac{V}{I} }\)
\(\large{ Ohms = \frac{Volts^2}{Watts} = R = \frac{V^2}{P} }\)
\(\large{ Ohms = \frac{Watts}{Amps^2} = R = \frac{P}{I^2} }\)

 

electrical symbols

Quantity	Symbol	Measuring Units	Description
Capacitance	\(C\)	Farad	unit of capacitance \(C=Q + V\)
Charge	\(Q\)	Coulomb	unit of electrical charge \(Q=C \; V\)
Conductance	\(G\;\)	Siemen	reciprocal of resistance \(G=1+R\)
Current	\(I\)	Amp	unit of electrical current \(I= \frac{V}{R}\)
Frequency	\(Hz\)	Hertz	unit of frequency \(f=1 + T\)
Impedance	\(Z\)	Ohm	unit of AC resistance \(Z^2=R^2 + X^2\)
Inductance	\(L\;\) or \(\;H\)	Volt	unit of inductance \(V_L=L \frac{di}{dt} \)
Power	\(P\)	Watt	unit of power \(P=V \; I\)
Resistance	\(R\) or \(\Omega\)	Ohm	unit of DC resistance \(R=V+I\)
Voltage	\(V\;\) or \(\;E\)	Volt	unit of electrical potential \(V=I \; R\)