(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The two headlights of a car require a total of 10 A supplied at 12 V. Given that the combustion of 1 L of gasoline releases 3X 10^7 J and that the conversion to electrical power has an efficiency of 25%, how much gasoline is consumed in one hour for this purpose alone?

2. Relevant equations

3. The attempt at a solution[/b

I'm not sure if what I did is right since I don't have the answers..but here I go:

-I first found the power by multiplying I X V...10 A X 12 V =120 W

-then I multiplied 120 W by 3600 seconds (an hour) to turn the answer into Joules...in this case 432000 Joules.

-Then I multiplied this by 0.25 to get 108 000 Joules.

-After this, I set a ratio with 1 L and 3X10^7 Joules with 108000 Joules and the unknown amount of gas. And I got 0.0036 L...

Is how I did it correct (i'm not really sure about the 25% part and the ratio part at the end...)

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Ohm's Law and power

**Physics Forums | Science Articles, Homework Help, Discussion**