Foundation Radio Amateur Licence - BDARS Online Syllabus

Ohm's Law explained

Ohm's Law is - A mathematical equation that shows the relationship between electric voltage, current and resistance. Ohm’s Law was named after Bavarian mathematician and physicist Georg Ohm.

Ohm’s Law can be stated as three mathematical equations, all derived from the same principle. In the following equations, V is voltage measured in volts, I is current measured in amperes and R is resistance measured in ohms:
V = I x R
R = V / I
I = V / R
Knowing any two of the values of a circuit, one can determine the third using Ohm’s Law. For example, if a circuit has a current of 2 amperes, and a resistance of 1 ohm, then according to Ohms Law, voltage equals 2 (V = 2 x 1).
Typically, Ohm’s Law is only applied to DC circuits and not AC circuits.

Note well: The letter “E” is sometimes used in representations of Ohm’s Law for voltage instead of “V.”


Type in the 
Current 

Amps 		 Type in the 
Resistance 

Ohms 		 This is the  
Voltage 

Volts
Type in the 
Voltage 

Volts 		 Type in the 
Resistance 

Ohms 		 This is the  
Current 

Amps
Type in the  
Voltage 

Volts 		 Type in the  
Current 

Amps 		 This is the  
Resistance 

Ohms