Question

The temperature co-efficient of resistance of a wire is 0.00125ºC. At 300 K, its resistance is 1W. The resistance of the wire will be 2W at –

• A. 1154 K
• B. 1100 K
• C. 1400 K
• D. 1127 K

Answer 1

Answer: (D)

1127 K

Answer 2

1W = R_2T = R₀(1 + a 2T) .... (i)

2W = R_T = R₀(1 + aT) ..... (ii)

2 = $\frac{1 + \alpha T}{1 + 2T\alpha}$, $\frac{2 + 54\alpha –1}{\alpha}$= T,

$\frac{1}{\alpha}$+ 54 = T; $\frac{100000}{125}$ + 54 = T, T = 854ºC

\ T = 854 + 273; T = 1127K