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Question #42715

Difficulty: 8/10 | 🟢 Free

The Question

A straight conducting wire is uniformly accelerated along its length (the +x+x direction) with a constant acceleration a0a_0. A uniform constant electric field of magnitude EE is applied along the +x+x direction within the wire. The conduction electrons have mass mm, charge −e-e, and an average relaxation time τ\tau between successive collisions with the lattice. Assume the standard Drude model where electrons lose their entire drift momentum relative to the lattice upon each collision, and the steady-state drift velocity is given by v⃗d=F⃗netτ/m\vec{v}_d = \vec{F}_{\text{net}}\tau/m. In the non-inertial frame of the accelerating wire, let PheatP_{\text{heat}} be the average rate of heat dissipation per electron, and PEP_E be the average rate at which the electric field does work on a single electron. Which of the following expressions correctly represents the difference (Pheat−PE)(P_{\text{heat}} - P_E)? (All given quantities are in standard SI units)

Options

  • A.

    a0(eE+ma0)τa_0 (eE + m a_0)\tau

  • B.

    a0(eE−ma0)τa_0 (eE - m a_0)\tau

  • C.

    12a0(eE+ma0)τ\frac{1}{2} a_0 (eE + m a_0)\tau

  • D.

    00

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Intuition_Breaker

Train your brain to resist "obvious" answers that are designed to deceive your intuition.

Concepts Behind This Question

Drift Velocity Mechanism|Work against Conservative Force|Frame of Reference

Why This Question Is Tricky

Common Mistakes

This question tests the application of the Work-Energy Theorem in a non-inertial reference frame within a dissipative system.

A common trap is assuming that Joule heating is always exactly equal to the work done by the electric field (P=J⃗⋅E⃗P = \vec{J} \cdot \vec{E}), leading students to incorrectly choose 0.

By placing the conductor in an accelerating frame, students must recognize that the pseudo force also does mechanical work on the electrons during their ballistic flight between collisions.

This additional kinetic energy is thermalized upon impact with the lattice, meaning the total heat dissipated exceeds the work done by the conservative electric field alone.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterCurrent Electricity - Class 12
ConceptDrift Velocity Mechanism
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree