Clear selection 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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20000J or 20kJ

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

igneous rocks also form where plates converge. the subducting plate melts as it sinks into the crust of the earth, and the melt rises into the overriding plate forming volcanoes. metamorphic rocks are formed mainly in the lithosphere, wherever there is high pressure and high temperature. -woods

= initial pressure

= final pressure = 2

= initial volume

= final volume = /4

= initial temperature = 20 c = 20 + 273 = 293 k

= final temperature = ?

using the equation