Lesson Plan

Define electric power and calculate it using P = IV

Derive and apply the alternative forms P = I²R and P = V²/R

Calculate electrical energy consumption and cost using E = Pt

Explain why power transmission lines use high voltage and low current

Interpret power ratings on household devices and calculate operating costs

19.4

"Power is the rate at which energy of any type is transferred; electric power is the rate at which electric energy is transferred in a circuit." "But a Coulomb per second (C/s) is an electric current, which we can see from the definition of electric current... Thus, the equation above tells us that electric power is voltage times current, or P = IV." "Thus, by combining Ohm's law with the equation P = IV for electric power, we obtain two more expressions for power: one in terms of voltage and resistance and one in terms of current and resistance." "This means that the physical characteristic of a circuit that determines how much power it dissipates is its resistance."