Question

280 J of electric energy flows into a certain light bulb every second and some energy is transferred into light energy while some ‘waste’ thermal energy is also generated. If 220 J of thermal energy is generated each second, what is the efficiency of this bulb?

Answer 1

Gives

Electric energy =280J

Thermal energy 229J

Efficiency $=\frac{thermal energy}{electric energy}$

Put values

$\eta=\frac{220}{380}\times100$

$\eta=57.89$ %