From 0e84fb8469ff10d813b743515c9ab347798afdc8 Mon Sep 17 00:00:00 2001
From: Erik Strand <erik.strand@cba.mit.edu>
Date: Wed, 13 Mar 2019 21:55:50 -0400
Subject: [PATCH] Add questions

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+---
+title: Problem Set 5
+---
+
+## (7.1)
+
+Cables designed to carry signals with minimum pickup of interference often consist of a twisted pair
+of conductors surrounded by a grounded shield. Why the twist? Why the shield?
+
+## (7.2)
+
+Salt water has a conductivity ∼4 S/m. What is the skin depth at $$10^4$$ Hz?
+
+## (7.3)
+
+Integrate Poynting’s vector $$P = E \times H$$ to find the power flowing across a cross-sectional
+slice of a coaxial cable, and relate the answer to the current and voltage in the cable.
+
+## (7.4)
+
+Find the characteristic impedance and signal velocity for a transmission line consisting of two
+parallel strips with a width $$w$$ and a separation $$h$$ (Figure 7.4). You can ignore fringing
+fields by assuming that they are sections of conductors infinitely wide.
+
+## (7.5)
+
+The most common coaxial cable, RG58/U, has a dielectric with a relative permittivity of 2.26, an
+inner radius of 0.406 mm, and an outer radius of 1.48 mm.
+
+### (a)
+
+What is the characteristic impedance?
+
+### (b)
+
+What is the velocity?
+
+### (c)
+
+If a computer has a clock speed of 1 ns, how long can a length of RG58/U be and still deliver a
+pulse within one clock cycle?
+
+### (d)
+
+It is often desirable to use thinner coaxial cable to minimize size or weight but still match the
+impedance of RG58/U (to minimize reflections). If such a cable has an outer diameter of 30 mils (a
+mil is a thousandth of an inch), what is the inner diameter?
+
+### (e)
+
+For RG58/U, at what frequency does the wavelength become comparable to
+the diameter?
+
+## (7.6)
+
+CAT6 twisted pair cable used in ethernet networks has a propagation delay of 4.6 ns/m, and an
+impedance of 100 ohms.
+
+### (a)
+
+What is the physical length of a minimum size 64 byte frame?
+
+### (b)
+
+Now consider what would happen if a “T” connector was used to connect one CAT6 cable to two other
+ones. Estimate the reflection coefficient for a signal arriving at the T.
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