Knowing 'Voltage' in a Circuit

The term "drop" here refers to the same concept as the voltage across an element, such as a resistor, LED, or even a switch. LEDs belong to the diode family and have a nominal voltage drop. Historically, this was approximately 0.7 volts, but now it ranges from 0.7 volts to 2.7 volts depending on the manufacturing process. You don’t need to memorize the voltage drop of an LED because, when designing almost anything, you’ll want to consult the component's datasheet for accurate specifications.

If you add up all the voltage drops in a circuit, they must equal the source voltage. This principle can easily be verified by measuring the voltage drops across each element in the circuit.