Ohms Law

Ohm’s Law is a fundamental principle in electronics that describes the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit. It is mathematically expressed as:

V = IR (Voltage = current * resistance)

From this equation, we can derive the following formulas:

Current = V / R
Resistance = V / I

Find the appropriate resistor size for a given voltage, forward voltage, and current (amperage): Forward voltage can usually be found in the datasheet of the component being used (like an LED).

resistance = (supply_voltage - forward_voltage) / current

Example (LED):

Supply voltage: 9v battery Forward voltage: 5.2v Desired current: 20Ma (.02A)

(9 - 5.2) / .02 = 190 Ohms