An automobile uses two halogen headlights 2

An automobile uses two halogen headlights connected as shown. Determine the power supplied by the battery if each headlight draws 3 A of current.

Image from: Irwin, J. David., and R. M. Nelms. Basic Engineering Circuit Analysis, Tenth Edition. N.p.: John Wiley & Sons, 2010.

Solution:

We know that each lamp draws 3 A of current, which means both lamps in total draw a total of 6 A of current.

The equation to determine power is P=VI where P is power, V is voltage and I is current. Substituting the values we know, we can write the following:

P=VI

P=(12V)(6A)

P=72W

This question can be found in Basic Engineering Circuit Analysis, 10th edition, chapter 2, question 2.8.