Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main 2004
Exam
JEE Main
Year
2004
Subject
Physics
Chapter
Thermal Properties of Matter

JEE Main 2004 · Physics · Thermal Properties of Matter

The thermo emf of a thermocouple varies with the temperature θ of...

The thermo emf of a thermocouple varies with the temperature θ\theta of the hot junction as E=aθ+bθ2\mathrm{E}=\mathrm{a} \theta+\mathrm{b} \theta^2 in volts where the ratio a/b\mathrm{a} / \mathrm{b} is 700∘C700^{\circ} \mathrm{C}. If the cold junction is kept at 0∘C0^{\circ} \mathrm{C}, then the neutral temperature is

Options

  1. A700∘C700^{\circ} \mathrm{C}
  2. B350∘C350^{\circ} \mathrm{C}
  3. C1400∘C1400^{\circ} \mathrm{C}
  4. Dno neutral temperature is possible for this thermocouple.

Correct answer

D. no neutral temperature is possible for this thermocouple.

Step-by-step solution

E=aθ+bθ2E=a \theta+b \theta^2 At neutral temperature dE/dθ=0\mathrm{dE} / \mathrm{d} \theta=0 ∴dEdθ=a+2 bθn=0;θn=−a2 b\therefore \frac{\mathrm{dE}}{\mathrm{d} \theta}=\mathrm{a}+2 \mathrm{~b} \theta_{\mathrm{n}}=0 ; \theta_{\mathrm{n}}=-\frac{\mathrm{a}}{2 \mathrm{~b}} Now ab=700∘C\frac{a}{b}=700^{\circ} \mathrm{C} (given) θn=−700/2=−350∘C\theta_n=-700 / 2=-350^{\circ} \mathrm{C} Now θc=0∘C\theta_c=0^{\circ} \mathrm{C}. So, θn>0∘C\theta_n>0^{\circ} \mathrm{C} But mathematically θn<0∘C\theta_{\mathrm{n}} < 0^{\circ} \mathrm{C}.
Practice Thermal Properties of Matter on Quantrex Academy →

More from Thermal Properties of Matter

As shown in the figure, an insulated container is fitted with a thermally conducting but… JEE Advanced 2026The heat extracted out of x gram of water initially at 50°C to cool it down to 0°C is… JEE Main 2026The temperature of a metal strip having coefficient of linear expansion α is increased… JEE Main 2026Which of the following best represents the temperature versus heat supplied graph for… JEE Main 202610 kg of ice at -10^ ∘ C is added to 100 kg of water to lower its temperature from 25 ^ ∘… JEE Main 2026A brass wire of length 2 m and radius 1 mm at 27^ ∘ C is held taut between two rigid… JEE Main 2026Rods x and y of equal dimensions but of different materials are joined as shown in… JEE Main 2026An aluminium and steel rods having same lengths and cross-sections are joined to make… JEE Main 2026 Full Thermal Properties of Matter list All JEE Main PYQs