Question

A rechargeable battery initially stores 3.6 kJ of chemical energy. Anna puts the battery in a flashlight, where 2.1 kJ of energy are transformed into light and heat. Then, Anna puts the battery in a charger, where 6.8 kJ of electrical energy are transformed into chemical energy. How much chemical energy is now stored in the battery?

Answer 1

8.3 kJ of energy is remaining in the battery.

Explanation:

According to conservation of energy, the tendency of energy is to convert it from one form to another. So if the battery has an energy of 3.6 kJ at first and then it has utilized as 2.1 kJ of energy. So after loosing this energy, it will be 3.6-2.1 = 1.5 kJ of energy.

Again it is stated that the battery is recharged with 6.8 kJ of energy.

Then the modified or the latest energy stored in the battery will be the sum of energy present in the battery after using flashlight with the energy added in the battery by charger.

So, the total energy stored in the battery = 6.8+1.5 = 8.3 kJ

Thus, 8.3 kJ of energy is remaining in the battery.