Which letter represents watt on the power wheel?

• A. P
• B. W
• C. Q
• D. R

Answer: (A)

Power is the quantity being represented, and its unit is the watt. In circuit notation, the letter used for this quantity is P. So on a wheel that maps letters to quantities, the one that stands for the wattage (the power) is P, since P denotes power and power is measured in watts. Remember the relationship P = V × I, which ties the letter P directly to the watt unit. The watt symbol W is the unit itself, but the letter used to label the quantity on the wheel is P.