Unformatted text preview: uniformly throughout its volume, the magnitude of the
potential difference Vb – V0 would
53%
A. increase B. decrease ALWAYS START FROM DEFINITION OF POTENTIAL
b ∆ V = − ∫ E ⋅ dr
0 C. stay the same Break integral into two pieces
a b ∆V = − ∫ E ⋅ dr − ∫ E ⋅ dr
0 conductor: = 0
insulator: 0 a same for conductor & insulator Physics 212 Lecture 29, Slide 9 RL Circuits 1 In the circuit below, V = 6 Volts, R = 10 Ohms, L = 100 mH. The
switch has been open for a long time. Then, at t = 0, the switch is
closed. What is the time constant for the current through the
inductor?
30%
A. R/L
B. R/2L
C. L/R
D. 2L/R
E. L/2R
I 2 I – I1 L
L dI1
− ( I − I1 ) R = 0
dt
IR = V − L 1 I1 2 L dI1
+ IR − V = 0
dt dI1
dt dI1
dI
− V + L 1 + I1R = 0
dt
dt 2L dI1
+ I1R = V
dt Strategy: Back to First Principles • The time constant is determined from a differential equation for the current through the inductor.
• Equation for current through inductor obtained from Kirchhoff’s Rules τ= " L" 2 L
=
" R" R Physics 212 Lecture 29, Slide 10 Faraday’s Law A rectangular wire loop travels to the right with constant velocity, starting in a region of no magnetic
field, moving into a region with a constant field pointing into the page (shaded rectangle below),
and continuing into a region of no magnetic field. Which plot below best represents the induced
current in the loop (Iloop) as it travels from the left through these three regions? Note: a positive Iloop
corresponds to a counterclockwise current. Current in...
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 Fall '08
 SELEN
 Physics, Electrostatics, Electric charge

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