PHYSICS · Multi-part · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Electromagnetic induction and alternating-current circuits · Electromagnetic induction and alternating-current circuits
Electricity, Magnetism and Electromagnetism, Ch Faraday's law, motional emf and Lenz's law
Problem
An air-cored toroid is wound with N=800 turns. Its core has a rectangular cross-section: inner radius a=8.0cm, outer radius b=10.0cm, height h=2.0cm. The winding carries a current that increases at the steady rate dI/dt=4.0As−1. Take the winding as dense enough that the field inside the core is the ideal toroidal field and the field outside the core is negligible. A second coil of 150 turns and resistance 4.0Ω is wound tightly round the core at one place, so that every one of its turns links the whole flux of the core. Its ends are joined by a resistor of 8.0Ω.
((a)) Find the rate of change of the magnetic flux through one cross-section of the core.
((b)) Find the magnitude of the emf induced in the 150-turn coil.
((c)) Find the current in the 150-turn coil's circuit.
((d)) The two ends of the 150-turn coil are labelled P and Q. Explain why the reading of a voltmeter connected to P and Q is not a property of P and Q alone, using what Chapter 3 required of a field before a potential difference could be defined.