Changing resistance and magnetic field · PhysicsBowl 2013 #35

Physics · electromagnetism

Problem

For the figure shown, the variable resistance of the inner circuit,

R

, is increasing at a constant rate. While this is occurring, in which direction is the magnetic field associated with the inner circuit at the point P in the plane of the circuit and in which direction is the flow of electrons through the resistor labeled

R_{ext}

Magnetic Field at P	Electron flow through $R_{ext}$
(A) There is no field	There is no flow
(B) Into the page	From Y to X
(C) Into the page	From X to Y
(D) Out of the page	From Y to X
(E) Out of the page	From X to Y

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