Honors Physics II
Problem Set 7b (due Wed Apr 13)
Spring 2016
[In all assignments this semester, you are advised to first look at worked out examples as well as
work out simple problems from your textbook before you attempt the homework problems
assigned.]
1. (i) At a given instant the current and the induced emf in an
inductor are as indicated in the figure. (a) Is the current increasing
or decreasing? (b) The emf is 17 V, and the rate of change of the
current is 25 kA/s; what is the value of the inductance?
(ii) The inductance of a closely wound N-turn coil is such that an emf of 3.0 mV is induced when
the current changes at the rate 5.0 A/s. A steady current of 8.0 A produces a magnetic flux of 40
µWb through each turn. (a) Calculate the inductance of the coil. (b) How many turns does the coil
have?
2. The current i through a 4.6-H inductor varies with time t as
shown. Calculate the induced emf during the time intervals (a)
t = 0 to t = 2 ms, (b) t = 2 ms to t = 5 ms, and (c) t = 5 ms to t =
6 ms. (Ignore the discontinuities at the ends of the intervals.)
3. In the figure, E = 100 V, R1 = 10 Ω, R2 = 20 Ω, R3 = 30 Ω, and
L = 2.0 H. Find the values of i1 and i2, (a) immediately after
switch S is closed, (b) a long time later; (c) immediately after
switch S is opened again; (d) a long time later.
4. A switch that connects a battery of emf E, a resistor of resistance R, and an inductor of
inductance L, are connected in series. Suppose that the inductive time constant of the circuit is
37.5 ms. The current in the circuit is zero at time t = 0. At what time is the rate at which energy is
dissipated in the resistor equal the rate at which energy is being stored in the inductor?
5. In an oscillating LC circuit, L = 1.13 mH and C = 3.88 µF. The maximum charge on the
capacitor is 2.94 µC. Find the maximum current.