A solid cylindrical conductor of radius 2.0 mm carries mobile electrons of number density

PHYSICS · Multi-part · CBSE · Physics · Current Electricity · Current Electricity

Problem

A solid cylindrical conductor of radius 2.0 mm carries mobile electrons of number density n=8.0×1028 m−3n=8.0\times10^{28}\,\text{m}^{-3}. In a laboratory demonstration the conductor is prepared so that, at an instant of time, electrons in the inner core of radius 1.0 mm drift to the right with speed v1=1.5×10−3 m s−1v_{1}=1.5\times10^{-3}\,\text{m}\,\text{s}^{-1}, while electrons in the outer cylindrical shell drift to the left with speed v2v_{2}. (a) Derive an expression for the net conventional current II through a cross-section of the wire in terms of v1v_{1}, v2v_{2}, nn, the elementary charge ee, and the specified radii. (b) Determine the value of v2v_{2} required so that the net current is zero. (c) Calculate the magnitude of the electric charge that crosses the mid-plane of the wire in a time interval of 2.0 ms for the inner core alone. (d) Despite your answer in part (b), explain why significant magnetic effects would still be produced in the space between the two cylindrical regions.

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