ES2210-01 Homework #3.
Remember to show all work. Some answers are given to help you check your solution. You only receive credit for work
shown, not for answers!
Problem 1. Obtain the equivalent resistance $R_{ab}$ for the circuit shown, and use it to find current $i$ and power supplied by
the 120 V source. Start by applying a wye-delta transform on the 5, 10, and 20 ohm wye. Then use series-parallel
simplifications to get $R_{ab}$. Please be sure to make separate drawings of your intermediate circuits and explain your steps
carefully.
Hint: Two of the delta resistances are 35 and 17.5 Ohms. The power is -1495 W.
a
12.5 $\Omega$
10 $\Omega$
5 $\Omega$
120 V
c
30 $\Omega$
15 $\Omega$
20 $\Omega$
b
Problem 2. Find $R_{ab}$ for the circuit in the previous problem, but this time begin by using a delta-wye conversion on the
delta giving by the 10, 5, and 12.5 ohm resistors.
a
12.5 $\Omega$
10 $\Omega$
5 $\Omega$
120 V
c
30 $\Omega$
15 $\Omega$
20 $\Omega$
b
b
Problem 3. In the above circuit, identify one other wye network that could be replace with a delta (you can just circle
the appropriate resistors), and redraw the circuit showing the delta replacement. You do not have to compute
component values.
Problem 4. In the above circuit, identify two other delta networks that could be replaced with wyes. Draw the two
corresponding circuits showing wye replacements. You do not have to compute component values.
