In the figure below there is a circular region of radius r_1 in which there is a
ID: 1497781 • Letter: I
Question
In the figure below there is a circular region of radius r_1 in which there is a uniform magnetic field B pointing out of the page (the magnetic field is essentially zero outside this region). The magnetic field is decreasing at this moment at a rate |dB/dt|. A wire of radius r_2 and resistance R lies entirely outside the magnetic-field region (where there is no magnetic field). In which direction does conventional current I flow in the ring? What is the magnitude of the current I ? (Use the following as necessary: r_1, r_2, R, and |dB/dt|)Explanation / Answer
clockwise
lenz law
flux=B*pi*r12
Emf=-d(flux)/dt =-d(B*pi*r12)/dt =-[d(B)/dt]*pi*r12
current =emf/resistance =[d(B)/dt]*pi*r12/R