Ideal vs Real

Electricity will always keep you on your toes. When working around electrical circuits your calculations used for troubleshooting are unlikely to perfectly match up with what you measure in the field, even if everything is functioning properly.

In this class, we will refer to these differences as ideal vs real. We calculate with ideal numbers to give us a baseline of what should to be happening in a circuit.  When we talk about ideal. We are talking about perfect.

 
 

Ideal sources

Constant voltage source

An ideal voltage source has a fixed output voltage meaning the value never changes. We use ideal sources to calculate electrical quantities when diagnosing or designing circuits.

For example, when calculating a small DC circuit we would use an ideal voltage of 1.5V for a AAA battery. For residential AC circuit that you’d find in your house, we would use 120V for the outlets and light sockets. These values are ideal.

In the real world these numbers would vary slightly if measured. Batteries slowly lose voltage as they die and the AC outlets in your house could measure anywhere from 114VAC to 126VAC.

 

Ideal components

An ideal component or load (resistor, capacitor, inductor) is used in the same way as an ideal source. We calculate and design based on the ideal values. If you are designing with a 10KΩ resistor component, you calculate based on the ideal number given (10,000Ω). But there is always a margin of error due to tolerances. In real life there are always variations, nothing is perfect, and nothing operates at 100% efficiency.

Tolerances describe how much variation a components real value might have compared to its ideal. (Real vs Ideal) Tolerances describe how accurate real values will be. For example, the 10kΩ resistor above might have a 10% tolerance, meaning its real value could be 10% higher or lower than the ideal 10,000Ω (9,000Ω-11,000Ω)


Ideal calculations give you IDEAL answers which represent values in perfect scenarios with perfect sources and perfect components even though we know all components have some variation, and are not perfect.

“We calculate with ideal numbers to give us a baseline of what should be happening in a circuit.”


Real values come from measurements. An example of a real value would be using a multi-meter to measure a light socket and the meter tells you 122.1V. This is acceptable and a common occurrence.