A common cell phone charger operates at 6.5V and consumes of 5W of power. a) Wha
ID: 1322036 • Letter: A
Question
A common cell phone charger operates at 6.5V and consumes of 5W of power.
a) What is the current flowing in the charger?
b) If it takes two hours to charge a phone completely, how much total energy was used?
c) If a 1 kg particle has the same amount of kinetic energy as your answer to part (b), how fast is it moving?
d) A claim was circulated on the internet recently which stated that a smartphone uses more energy than a refrigerator. Given that refrigerators consume about 750 W of power, and assuming that a phone is charged once a day, is this claim correct? (Hint: Unsourced scientific claims circulated on the internet are rarely, if ever, true. However, to answer the question you should calculate the average wattage of the cell phone.)
Explanation / Answer
As we know that
P = VI
Therefore
I = P/V
= 5/6.5
= 0.769 A
=========================================================
Energy = P*t
= 5*2*60*60
= 36000 J
=================================================
Kinetic Energy = 0.5*m*v^2
36000 = 0.5*1*v^2
v = 268.328 m/sec
=================================================
Energy Consumed by the movile phone = P*t
= 5*2*60*60
= 36000 J
Energy Consumed by refrigerator = P*t
= 750*24*60*60
= 64800000 J
No the claim is not true Because Power consumed by refrigerator is more
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