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The maximum current that flows through a fuse wire, before it blows out, varies with its radius 'r' as -

(a) r3/2  

(b) r

(c) r2/3

(d) r1/2

 

Please answer in detail

Anurag Kishore , 14 Years ago
Grade 12
anser 1 Answers
Najbul Gazi

Last Activity: 3 Years ago

Option -(a) r^(3/2) 
  The heat produce by the fuse wire= i^2R= i^2* row*L/(π*r^2) 
Now, the rate of loss of heat from the fuse wire by radiation= Emissivity* Area * Excess temp. Over surrounding=e*2πrL*theta
 
Before the fuse will be blown out, 
   The heat produce in fuse wire = rate of loss of heat from the fuse
So, i^2*row*L/(πr^2) =e*2πrL*theta
  i^2 = [e*2πrL*theta*πr^2]/[row*L]
 Clearly, i^2 proportion r^3
And i proportion to r^(3/2) 
 

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