Question

The temperature coefficient of resistivity of a material is 4 × 10^–4 / K. When the temperature of material is increased by 50⁰C, its resistivity increases by 2 × 10^–8 Wm. The initial resistivity of material (in ohm-metre) is –

• A. 50 × 10^–8
• B. 90 × 10^–8
• C. 100 × 10^–8
• D. 200 × 10^–8

Answer 1

Answer: (C)

100 × 10^–8

Answer 2

r_T = r₀ (1 + aDT)

r_T – r₀ = r₀ a DT

\ r₀ = $\frac{\Delta\rho}{\alpha\Delta T}$ = $\frac{2 \times 10^{- 8}}{4 \times 10^{- 4} \times 50}$ = 10^–6 W–m