How Effective Are Human-Powered Chargers for Everyday Use?

[azler]

Homework Statement

Can some one please help me out on this, i can't seem to get my head around it.

Regards,
Rob

 

[arkofnoah]

tell me what you've done so far.

 

[xcvxcvvc]

do you know the equation for efficiency? if not, do you think you can derive it? if a system were 0 percent efficient(0.00), you'd need to supply infinite energy to reach any finite stored energy. If the system were 100% efficient (1.00), you'd need to supply Z joules to store Z joules. Can you think of a relationship between P_in and P_stored that relies on the 0 to 1.00 representation of efficiency that would produce the end behavior we just explored?

 

[azler]

Hi Sorry about the late reply i have been away.
I have not managed to do any thing on this question it has stumped me from he start.
It says a human power charger is used but not what charger so i am assuming i can make on up? for instance a bike powered charger?
Any info to get me started would help me a lot.
Regards,
Rob