The resistances of the platinum wire of a platinum resistance thermometer at the ice point and steam point are $8 \Omega$ and $10 \Omega$ respectively. After inserting in a hot bath of temperature $400^{\circ} \mathrm{C}$, the resistance of platinum wire is :

JEE Main · 2024 · 04 Apr 2024 · Shift 1 · Current Electricity

The resistances of the platinum wire of a platinum resistance thermometer at the ice point and steam point are

8Ω

and

10Ω

respectively. After inserting in a hot bath of temperature

40 0^{\circ} C

, the resistance of platinum wire is :

Answer: (B)

Resistance varies with temperature as

R_{t} = R_{0} (1 + α t)

, with

R_{0} = 8 Ω

(ice point).

From the steam point (

10 0^{\circ}

C):

10 = 8 (1 + 100 α) \Rightarrow 100 α = \frac{1}{4} .

40 0^{\circ}

R_{400} = 8 (1 + 400 α) = 8 (1 + 4 \times \frac{1}{4}) = 8 (1 + 1) = 16 Ω.

Option B.

JEE Main · 2024 · 04 Apr 2024 · Shift 1 · Single correct option