ECE 2300 – CIRCUIT ANALYSIS
HOMEWORK #3
1.
a) Find the power delivered by the source in this circuit.
b) Find the voltage
v
X
.
+

v
S
=
9[V]
R
1
=
1[k
Ω
]
R
2
=
2.7[k
Ω
]
R
3
=
1.5[k
Ω
]
R
5
=
3.3[k
Ω
]
R
4
=
5.6[k
Ω
]
R
6
=
2.2[k
Ω
]
+

v
X
(PWA Problem 1 in Module 2)
2.
A voltmeter is used in series with a resistor to obtain a new voltmeter with the ability to read
a higher voltage.
The combination is given in the circuit here.
The original voltmeter has a
meter resistance of 10[k
Ω
], and reads up to 2[V] fullscale.
a)
The goal is to have a new voltmeter that can read up to 50[V].
What value of resistor
R
V
should be used to make this happen?
b)
When 18[V] is applied to this series combination, with
R
V
as found in part a), what will the
original voltmeter read on the 2[V] scale?
(PWA Problem 7 in Module 2)
Next slide
Voltmeter
R
V
v
T
+

v
M
+

B
A
V
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3.
A measurement of an unknown resistor
R
X
is attempted using a voltmeter and an ammeter, as
shown in the circuit here.
The intention is to simultaneously measure the current through the
resistor with the ammeter, and the voltage across the resistor with the voltmeter.
The resistance
will then be obtained from the ratio of these two readings.
For this problem, assume that the
meter resistance for the ammeter is 100[
Ω
], and for the voltmeter is 10[k
Ω
].
a)
Find the ammeter reading, if
R
X
is 2.7[k
Ω
].
b)
Find the voltmeter reading, if
R
X
is 2.7[k
Ω
].
c)
Find the ratio of the voltmeter reading to the ammeter reading.
d)
How much error is there in this resistance measurement?
e)
What resistance is this technique really measuring?
(PWA Problem 8 in Module 2)
4.
A voltmeter has a fullscale reading of 5[V], and a resistance of 50[k
Ω
].
Consider each of the
following cases, one at a time, for the circuit shown below.
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 Spring '08
 Staff
 Volt, Resistor, Electrical resistance, Series and parallel circuits, Ammeter

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