• Circuit analysis can be troubling because we are dealing with particles that have never been seen. We depend upon calculations and approximations to determine what is happening inside the circuit, and measuring instruments to verify our numbers.
• Current and voltage are very important terms that are not well understood by the beginner. Consider an electron/proton pair. If both are together they are stable and steady. If we separate them they exert a force of attraction, much like gravity. This potential of attraction is called voltage. If we create a channel for these electrons to flow back to the protons (electrons are much lighter and more mobile than protons), the flow of electrons is called a current. The electrons do not flow freely, the restriction of flow is called resistance.
• All of us have seen an electromagnet at least once in our lives. This is effectively a large inductor. The device is best described as resisting current flow changes (almost as if preserving the momentum of the current). The resulting relationship is,
• When you get a static shock you are touching a basic form of capacitor. An electrical capacitor typically allows current to flow freely when a voltage is applied, but the current will quickly reach a steady state. The relationship is,
• Voltage sources are also very common. Disposable batteries (e.g, 1.5V, 9V) are one good example. When we use these normally we assume that the batteries will supply any amount of current, at the rated voltage. The schematic symbol is shown below,