Resistance of the wire is measured as 2Ω and . . .

Question : Resistance of the wire is measured as 2Ω and 3Ω at 10°C and 30°C respectively. Temperature co-efficient of resistance of the material of the wire is 
(a) 0.033 
°C-1
(b) -0.033 
°C-1
(c) 0.011 
°C-1
(d) -0.055 
°C-1

Doubt by Suhani

Solution :
Here
α= ?
R=2Ω
R'=3Ω
T=10°C
T'=30
°C

We know, 
R=R₀[1+α(T-T₀)
Case I
R=R₀[1+α(10-0)]
2=R₀[1+α(10)]
2=R₀[1+10α]  — (1)

Case II
R'=R₀[1+α(T'-T₀)
3=R₀[1+α(30-0)]
3=R₀[1+α(30)]
3=R₀[1+30α] — (2)

Dividing Equation (2) by (1)

3/2=R₀[1+30α]/R₀[1+10α]
1.5=[1+30α]/[1+10α]
1.5+15
α=1+30α
1.5-1=30
α-15α
0.5=15
α
0.5/15=
α
1/30=
α
α=1/30
α=0.033 °C-1

Hence, (a) 0.033 °C-1 would be the correct option.