Grade 12th passElectric Current

fuse has a high resistance why?
How it depends upon the high resistance?

Rahul

7 Years agoGrade 12th pass

1 Answer

anil

7 Years ago

They have a relatively low resistance compared to the circuit they are protecting, otherwise they would dissipate too much power and fuse. They have to be higher than all other conductors in the circuit or otherwise an accidental fuse will blow somewhere else. The lower the fuse current rating, the higher the resistance is. A traditional wire fuse works using dissipated power P = I*I*R. (I want to I squared R but I can't do superscript on this tablet!). When the current reaches the prescribed level then the power dissipation is enough to heat the fuse wire, increasing the resistance of the wire with temperature (all metals get higher resistance with temperature), which in turn dissipates more power. This soon reaches a critical temperature where the wire melts and the fuse blows.