Flowing current causes magnetic fields. Magnetic force is proportional to the current flow, ignoring non-ideal effects. Magnetic force causes valve spool and electric motor movement. Just as forcing fluid through a restriction generates heat, forcing current through resistance also generates heat. The heat is measured in wattage .
Inductance is the property of a coil resisting changes in current flow.
Capacitance is the property of a capacitor resisting changes in voltage. Feel free to fast forward past the next section, but remember where to find it when you need it. No formulas involving magnetism, inductance or capacitance are presented as they usually involve calculus, seldom are useful to consumers of electronics, and understanding that level of detail is why you pay us. How to hook it up Current insists on being able to flow back to where it started from, thus the name circuit. You must have two wires hooked up to work.