Question

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10 points
A laptop battery stores energy with an efficiency of 80%. If 16 000 J of
energy are transferred to the laptop from the battery, how much energy
must have been transferred to the battery?
20 kJ
20 J
1.28 kJ
12 800 J
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Answer 1

20000J or 20kJ

Step-by-step explanation:

Given parameters:

Efficiency of the battery = 80%

Amount of energy transferred = 16000J

Unknown:

How much energy was transferred to the battery = ?

Solution:

Since the battery is 80% efficient, it loses 20% of energy anytime it wants to store energy.

Now, 16000J of energy is contained in the battery, the original amount of energy sent to the battery;

Let the amount of energy sent to the battery be y

80% of y = 16000

0.8y = 16000

y = 20000J or 20kJ