Overview:

This page will focus on the topic of efficiency:

Efficiency- is a measure of how much work or energy is conserved in a process. In many processes, work or energy is lost, for example as waste heat or vibration. The efficiency is the energy output, divided by the energy input, and expressed as a percentage. A perfect process would have an efficiency of 100%.

Efficiency

No process transfers 100% of its energy (unless its to heat).

We can define the efficiency of a process as

 

h  =  usefuloutput work   =  useful power output

             total input work         total power input

 

Expressed as a %, efficiency    =   useful output   x  100 %

                                                             total input

Example 

100 J of electrical energy is supplied to a 100 W light bulb every second. Of this, only 10 J is transferred to the surroundings as light energy. The rest, is transferred to the surroundings as heat energy.  Calculate the efficiency of the light bulb.

h  =  useful output work   =  useful power output

           total input work            total power input

h =     10 J x 100 %  =  10 %

          100 J 

NB: A 100% efficient light bulb would convert all the electricity to light and not produce any heat at all

AlAnoud AlYazeedi
29 April 2019 at 19:03

You provided an example in this section. I suppose you forgot to add examples in the three previous sections ( work, power, and energy). 

 

Ahmed Hasnain
8 May 2019 at 21:31

Hi,

i personally found your e-portfolio to be very professional, you had all the external media inputted into your portfolio which was fantastic. i liked the fact that you have added a example question however you did not do this for all the other sections of the topic. 

 

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