This diagram shows four sine waves one above the other. The top one is labeled V p and begins at zero at the left end and goes up. The second wave is labeled I p and begins at minus 1 at the left end. This wave lags the wave above it by 90 degrees. The next wave is labeled V s and is in phase with the wave above it. The fourth and last wave lags the wave above it by 90 degrees. It begins at zero and goes down. End verbal description.