Question

the resistance of bulb at 30 degrees is 30 ohms. Find at 0 degree Celsius.​

Answer 1

Answer:-

Given: The resistance of a conductor at 20∘C is 3.15Ω and at 100∘C is 3.75Ω.

To find the temperature co-efficient of resistance of the conductor.

Solution:

Here R20​=3.15,R100​=3.75

We know that Rt​=R0​(1+αt)

where R0​= resistance at 0∘C

and Rt​= resistance at t∘C

α= temperature coefficient of resistance

Now,

R20​=3.15=R0​(1+20α)....(i)

R100​=3.75=R0​(1+100α)....(ii)

Dividing (i) and (ii), we get

R0​(1+100α)R0​(1+20α)​=3.753.15​⟹3.75(1+20α)=3.15(1+100α)⟹3.75+75α=3.15+315α⟹240α=0.6⟹α=0.0025∘C−1

From equation(i) ,

R0​=1+20α3.15​⟹R0​=1+20(0.0025)3.15​⟹R0​=1+0.053.15​⟹R0​=3Ω

is the temperature co-efficient of resistance of the conductor.

Hope it works..!!

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