Question

A bulb converts 9J of energy in each second from an input of 100J of energy. Calculate efficiency of this light bulb

Answer 1

Efficiency is calculated through dividing the actual mechanical advantage by the hypothetical mechanical advantage:

- the actual mechanical advantage is 9J because that's how much work the light bulb doing

- the hypo. mechanical advantage is 100J. Ideally, in a perfect world, the light bulb can convert 100J input into 100J output, but do to resistance and other factors it is not possible.

$\frac{9}{100} = .09$
change the decimal to a percentage:

$.09 = 9\%$
the light bulb had 9% efficiency