1.1
ECE 2300 – CIRCUIT ANALYSIS
HOMEWORK #1
1.
The diagram in Figure P1.1 shows the electrical connection of two devices.
The current
i
X
and the voltage
v
X
are shown.
Assume that the current
i
X
(t)
is a current made up of the flow of
electrons.
Assume that
1
475[s ]
( )
42[mA]
25[mA] ; for
0, and
( )
3.75[V]; for
0.
t
X
X
i
t
e
t
v
t
t
a)
Is Device 1 in the active or passive sign convention with respect to
i
X
and
v
X
?
b)
Which way are the electrons moving through Device 2 at
t
= 1[ms]?
c)
Which way are the electrons moving through Device 1 at
t
= 5[ms]?
d)
What is the power absorbed by Device 2 for
t
> 0?
e)
Are the electrons gaining or losing energy as they move through Device 1, at t = 3[ms]?
f)
What is the energy delivered by Device 2 for the time period 0 <
t
< 2[ms]?
g)
What is the energy delivered by Device 1 for the time period 2[ms] <
t
< 10[ms]?
Device 2
i
X
(t)
v
X
(t)
+

Device 1
2.
The diagram shown in Figure P1.2 shows a model for a car’s electrical system.
The current
i
B
and the voltage
v
B
are given as
1
2.3[s ]
5[A]
5[A] ; for
0, and
rad
14[V]cos(3.7[
] ); for
0.
s
t
B
B
i
e
t
v
t
t
a)
Is the battery in the active or passive convention with respect to
i
B
and
v
B
?
b)
How much energy is absorbed by the battery in the first second after
0
t
?
Rest of the
Car
i
B
(t)
v
B
(t)
+

Battery
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3.
The voltage in a wall socket has been measured, and found to be equal to
A blender is connected to this wall socket, and the current in the blender is measured and found
to be
The diagram shows the voltage and current
polarities in this connection.
a)
Find the power absorbed by the blender
at
t
= 0.
b)
Find the power absorbed by the blender
at
t
= 4.3[ms].
c)
Find the power absorbed by the blender
at
t
= 8.6[ms].
d)
Find the energy absorbed by the blender
over one cycle of the sinusoid.
(PWA Problem 1 in Module 1)
4.
The diagram below shows a model for a car’s electrical system.
The current
i
B
and the
voltage
v
B
are given as
1
2[
]
10
5 [A]; for
0, and
14[V]; for
0.
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 Fall '08
 Staff
 Conservation Of Energy, Energy, Volt

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