Final answer:
The equation for power delivered to a load resistor by a constant voltage source is P = V² / R, derived by substituting Ohm's law (I = V/R) into the basic power formula P = IV.
Step-by-step explanation:
The equation for power delivered to a load resistor by a constant voltage source is P = V² / R, where P is the power, V is the voltage across the resistor, and R is the resistance of the resistor. To derive this, we start with the basic power formula P = IV (power equals current times voltage). Using Ohm's law, which states that I = V/R (current equals voltage divided by resistance), we substitute I in the power formula, yielding P = (V/R)V or simplifying to P = V²/R. Another related formula is P = I²R, where I is the current through the resistor.