Question

Mcq resistance of a wire at 20 degree celsius is 20 ohm and at 500 degree celsius is 50 m at what temperature its resistance is 25 ohm please give me answer

Answer 1

Ilet R1 be resistance in First case and temperature be t1.
let at t2 temperature resistance will be r2.
.and temperature coefficient of resistance be alpha.
now Given.
R1= 20ohm
R2 = 25ohm
t1= 500 27°C .
t2= ?.
see picture!!for solution!!....
since t2 is 625° C
hope it helped you!!....

Answer 2

Answer

Use , R(t)=R(1+at). ( a = alpha )

20 = R(1+20a). --------(i)

60 = R(1+500a). --------(ii)

Divide both equation ,

60/20 = 1+20a/1+500a

So,from this we get a = 0.0045

Then for 25°c the equation is

25 = R(1+at). --------(iii)

Divide (iii) and (i) equation we get

25/20 = 1+at/1+20a

5/4 = 1+at/1+20a

5(1+20a) = 4(1+at)

Solving this we get

t = 80°c

Explanation: