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Question #43360

Difficulty: 8/10 | 🟢 Free

The Question

Two identical perfectly black spherical resistors, each of surface area AA, are placed in a vacuum chamber whose walls are maintained at absolute zero (0 K0\text{ K}). The electrical resistance of each sphere varies with its absolute temperature TT according to the relation R(T)=R0(TT0)R(T) = R_0 \left(\frac{T}{T_0}\right), where R0R_0 is the resistance at a reference temperature T0T_0. Resistor 1 is connected to an ideal constant current source I0I_0, while Resistor 2 is connected to an ideal constant voltage source V0V_0. It is given that V0=I0R0V_0 = I_0 R_0. Let the initial power dissipated at temperature T0T_0 be P0=I02R0=V02R0P_0 = I_0^2 R_0 = \frac{V_0^2}{R_0}. If P0=η(AσT04)P_0 = \eta (A \sigma T_0^4), where σ\sigma is the Stefan-Boltzmann constant and η\eta is a dimensionless positive constant, what is the ratio of the steady-state power dissipated by Resistor 1 to the steady-state power dissipated by Resistor 2, P1P2\frac{P_1}{P_2}?

Options

  • A.

    η8/15\eta^{8/15}

  • B.

    η2/15\eta^{2/15}

  • C.

    11

  • D.

    η4/5\eta^{4/5}

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Multi-Concept_Bridge

Master problems that require linking physics and math concepts to solve complex competitive questions.

Concepts Behind This Question

Power Dissipation Ratio|Stefan-Boltzmann Power Law|Integration

Why This Question Is Tricky

Common Mistakes

This question tests the student's ability to couple electrical power dissipation with the Stefan-Boltzmann law under different circuit constraints (constant current vs. constant voltage).

The primary trap lies in assuming that since the initial power P0P_0 is identical for both resistors, their steady-state power dissipation will also be identical (leading to a ratio of 1).

Students often fail to recognize the feedback loop: temperature changes the resistance, which in turn alters the power dissipated differently depending on the source.

For a constant current source, power increases with temperature (P∝RP \propto R), whereas for a constant voltage source, power decreases with temperature (P∝1/RP \propto 1/R).

Solving the resulting non-linear equilibrium equations (T4∝TT^4 \propto T vs T4∝1/TT^4 \propto 1/T) is required to find the true steady-state power ratio.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterCurrent Electricity - Class 12
ConceptPower Dissipation Ratio
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree