Question

An automotive Battery is rated at120 A-h. This means that under certain test conditions, it canoutput 1 A at 12 V for 120 hours.

Answer 1

Answer:

Part A:

In W-h:

Energy Stored=1440 W-h

In Joules:

$Energy Stored=5.184*10^6Joules\\Energy Stored=5.184 MJ$

Part B:

In W-h:

Energy left=240 W-h

In Joules:

Energy left= 8.64*10^5 J

Explanation:

Part A:

We are given rating 120A-h and voltage 12 V

Energy Stored= Rating*Voltage              (Gives us units W-h)

Energy Stored=120A-h*12V

Energy Stored=1440 W-h

Converting it into joules (watt=joules/sec)

Energy Stored=$1440 Joules * \frac{3600sec}{h}h$

Energy Stored=5184000 Joules

$Energy Stored=5.184*10^6Joules\\Energy Stored=5.184 MJ$

Part B:

Energy used by lights for 8h=150*8

Energy used by lights for 8h=1200W-h

Energy left= Energy Stored(Calculated above)- Energy used by lights for 8h

Energy left=1440-1200

Energy left=240 W-h

Energy left=$240 Joules * \frac{3600sec}{h}h$

Energy left=864000 Joules

Energy left= 8.64*10^5 J