Power dissipated by a battery and bulb

Question: If a 9.0-volt battery causes 1.0 A to flow through a alightbulb, how much power is dissipated?

Solution: The voltage rating of a battery tells us what voltage edifference ΔV it is designed to maintain between its terminals.

The only nontrivial thing in this problem was dealing with the units. One quickly gets used to translating common combinations like A.V into simpler terms.