Answer: 120 J
Explanation:
The law of conservation of energy states that energy cannot be created nor destroyed, but only converted into other forms.
In this problem, we have an initial amount of electrical energy, E, converted into two forms of energy: light energy (L) and heat (H). For the law of conservation of energy, we have:
[tex]E=L+H[/tex]
So, we can find the initial amount of electrical energy:
[tex]E=20 J+100 J=120 J[/tex]
