Fall 2012 Midterm 3 Solutions

# Immediately after opening the switch what is the rate

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: t is the rate (in Joules/s = Watts) at which magnetic energy stored in the inductor, L, is decreasing? 12 V L 2 mH 60 Ω 20 Ω A) B) C) D) E) 1. calculate current in inductor immediately before the switch is opened. 29 W 0W 48 W 7W 15 W This is the current that must go through the two resistors when the switch is opened. Use it to calculate power. Version 1 Page 9 The rate that energy in the inductor decreases is equal to the power dissipated in the two resistors because that is where the energy is going. 16. Current I is charging a circular parallel plate capacitor with plate radius of R. The circulation of the magnetic field, B dl , around a coaxial circular path between the plates with r = R/3 has some definite value. Consider two surfaces bounded by this circular path; the round flat surface (shaded); and the open soup-can (dashed). What can we conclude from the Ampere-Maxwell Law? The total current of all kinds flowing in to the cylinder must be exactly equal to the total current of all kinds flowing out. (this is a paraphrase of the Kirchhoff junction rule). I The cylinder only covers 1/9 of the area of the capacitor plate. This means only 1/9 of the displacement current of the capacitor goes through the shaded side. To make up the difference 8/9 of current must go out the sides in the form of conduction current (remember, the charge has to spread out across the entire plate...). A) The &quot;current&quot; (conduction + displ...
View Full Document

## This document was uploaded on 03/11/2014 for the course PHYSICS 240 at University of Michigan.

Ask a homework question - tutors are online