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H=V 2 /R =>H α 1/R, Potential Difference and time remaining constant Therefore, heat produced is more if R is less. R=ρl/A =>R α 1/A Therefore, heat produced is more if A is more. [Because, R decreases if A increases which in turn produces more heat.] More heat would produce more light. Therefore more A would produce more light. Then why are filaments used in bulb made thin i.e. their A is made less? Notations: A-area of cross section R-Resistance H-Heat Ρ-restivity

 


      H=V2/R


=>H α 1/R, Potential Difference and time remaining constant


Therefore, heat produced is more if R is less.


R=ρl/A =>R  α  1/A


Therefore, heat produced is more if A is more.  [Because, R  decreases if A increases which in turn                                                 produces more heat.]


More heat would produce more light.


Therefore more A would produce more light.


Then why are filaments used in bulb made thin i.e. their A is made less?


Notations:


A-area of cross section


R-Resistance


H-Heat


Ρ-restivity

Grade:10

2 Answers

great king
27 Points
13 years ago

it depends upon the elements used the tugstun is used which have maximum capacity to withstand the heat and not melt certain temperature is required for it to heat up thats why there is no 100 %  guarantee it fuses

bhanuveer danduboyina
95 Points
13 years ago

because filaments should have high resistance and low melting point 

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