Hello,

Solution :

The resistance and temperature relation is given by ,

Rt = R0 ( 1+ αt )

By electric resistance thermometer.

R0 - resistance at 0° C

R0= 2 ohm

R100 = 3 ohm

So,

2 =R0(1+α*0)

3 = R0 (1+ α*100)

By Cross multiplication,

2+ 200α= 3

200α = 3-2

200α = 1

So, α = 1/200 = 0.005

Now,

R = 5 ohm

5 = 2 ( 1+ 0.005t)

5 = 2 + 0.01t

5-2 = 0.01t

3 = 0.01t

3 = 1/100 t

t = 3*100

t = 300° C

So,

when resistance indicates 5 ohm the temperature will be 300° C

Hope it helps