The current through an element is given in the figure below (bold line).
What is the net charge that passes through the element between t = 4 and t = 8 seconds?
Fall 2013, Exam #1, Problem #1(a)
Answer: 24 C
1
The charge entering the positive terminal of an element is given in the figure below.
Estimate the current through the element between t = 5 and t = 7 seconds.
Fall 2013, Exam #1 sample, Problem #1(c)
Answer: –4 A
2
The charge that has passed through a wire is plotted in the figure.
Sketch the corresponding current through this wire.
Fall 2014, Exam #1, Problem #1(a)
 9 mA 0  t  2 μs

Answer: i  t    0 mA 2  t  4 μs
6 mA 4  t  7 μs

3
The voltage drop across an element is 4 mV and the current through the element (along the drop)
is 10 mA. Calculate the electrical energy absorbed by the element over 8 ms.
Fall 2014, Exam #1, Problem #1(b)
Answer: 320 nJ
4
For the circuit below, the scale of the voltmeter is Volts (V) and the scale of the ammeter is
milli-Amps (mA).
(a)
(b)
(c)
(d)
Determine the value of the resistance, R .
Compute the power absorbed by the voltage source.
Calculate the amount of charge that passes through the ammeter over 8 seconds.
If the resistance is doubled, but the voltage and current source do not change, does the
reading on either meter change? If so, which one(s) change(s) and what is the new
reading?
Fall 2014, Quiz #1
Answers: (a) 10 k , (b) 6 mW , (c) 4 mC , (d) voltmeter, 10 V
5
In the figure below is a plot of current flowing into a capacitor plate over time. The decay of this
current is exponential, for all time. At t = 15 seconds, the current has decayed to approximately
5% of its initial value. Determine the total charge that has accumulated on the capacitor plate at
t = 5 minutes.
Fall 2014, Take-home exam, Problem #1
Answer: 10 mC
6
Given measurements of voltage and current in the figure (for a single element, and in accordance
with the passive sign convention), determine this element’s resistance.
Fall 2014, Final exam, Problem #3(b)
Answer: 100 k
7
The time-varying current through an electrical element is plotted below. The voltage across the
element, in accordance with the passive sign convention, is 5 Volts.
(a)
(b)
(c)
(d)
Calculate the total charge that passes through the element between t = 0 and t = 8 s .
Calculate the net charge that passes through the element between t = 0 and t = 8 s .
Sketch the power absorbed by the element between t = 0 and t = 8 s .
Determine the net electrical energy absorbed by the element between t = 0 and t = 8 s .
Fall 2014, Final exam review, Problem #18
Answers: (a) 10 nC , (b) 6 nC , (d) 30 nJ
8
Assuming a global population of 9 billion people, each using approximately 100 W of power
continuously throughout the day, calculate the total land area that would have to be set aside for
photovoltaic power generation, assuming 800 W/m2 of incident solar power and a conversion
efficiency (sunlight to electricity) of 10%.
Fall 2013, Homework #1, Problem #3
Answer: 1.125 x 104 km2
9
Determine the power absorbed by each of the elements below.
Fall 2013, Homework #1, Problem #3
Answers: (a) –2 W , (b) –47.1 mW , (c) –200 W
10
Refer to the circuit given below, while noting that the same current flows through each element.
The voltage-controlled dependent source provides a current which is 5 times as large as the
voltage Vx . (a) For VR = 10 V and Vx = 2 V , determine the power absorbed by each element.
(b) Is element A a passive or an active source? Why?
Fall 2013, Homework #2, Problem #1
Answers: (a) pVx = –20 W , pVR = 100 W , p5Vx = –80 W , (b) passive, absorbs power
11
The circuit depicted below contains a dependent current source; the magnitude and direction of
the current it supplies are directly determined by the voltage labeled v1 .
Note that therefore i2 = –3v1 . Determine the voltage v1 if v2 = 33i2 and i2 = 100 mA .
Fall 2013, Homework #2, Problem #5
Answer: –33.3 mV
12

0

2t
The total charge, in coulombs, that enters the terminal of an element is 

2 t  2 
3  e
Find the current and sketch its waveform for t  0 .
Fall 2014, Homework #1, Problem #1

0A
t0

2A
0t 2
Answer: i  t   

2 t  2 
A
t2
2e
13
t0
0t 2 .
t2
The current through and voltage across an element vary with time as shown in the figure below.
(a) Sketch the power delivered to the element for t > 0 . (b) Determine the total energy
delivered to the element between t = 0 and t = 25 s . The element voltage and current adhere to
the passive convention.
Fall 2014, Homework #1, Problem #3
Answers: (a)
, (b) 5833 J
14
An electric heater is connected to a constant 250-V source and absorbs 1000 W. Subsequently,
this heater is connected to a constant 220-V source. (a) What power does it absorb from the
220-V source? (b) What is the resistance of the heater?
Fall 2014, Homework #1, Problem #4
Answers: (a) 62.5  , (b) 774 W
15
A current source and a voltage source are connected in series with a resistor as shown in the
circuit below. All of the elements connected in series have the same current is in this circuit.
Suppose that vs = 10 V , is = 3 A , and R = 5  . (a) Calculate the voltage v across the resistor
and the power absorbed by the resistor. (b) Change the voltage source to vs = 5 V and
recalculate the voltage v across the resistor and the power absorbed by the resistor.
Fall 2014, Homework #1, Problem #5
Answers: (a) 15 V , 45 W , (b) 15 V , 45 W
16
The following experimental data is acquired for an unmarked resistor, using a variable-voltage
power supply and a current meter. The current meter readout is somewhat unstable,
unfortunately, which introduces error into the measurement.
(a) Plot the measured voltage-versus-current characteristic.
(b) Using a best-fit line, estimate the value of the resistance.
Fall 2013, Homework #2, Problem #2
Answers: (a)
, (b) 2 k
17
The amount of charge contained in a device over time is 10t 2  22t  mC 
where t is in seconds. Sketch the current through the device during 0  t  5 s .
Fall 2015, Homework #1, Problem #1
Answer: i(t) = 10t – 22 mA
18
The current through a light bulb as a function of time is 114sin 100 t   A  .
Determine the net charge transported through the bulb in 10 milliseconds
(immediately after t = 0 ).
Fall 2015, Homework #1, Problem #3
Answer: 726 mC
19
In the first circuit depicted, vs = 15 V, is = 4 A, and R = 5  .
Calculate the current i through the resistor.
Fall 2015, Homework #1, Problem #4
Answer: 3 A
20
A plot of current into a capacitor plate is given. The charge on the plate at t = 2 s is 0 C .
Determine the charge on the plate at t = 6 s .
Fall 2015, Exam #1, Problem #4
Answer: 30 nC
21
The battery of a flashlight provides 3 V to the bulb, and the resistance of the bulb is 15 .
Determine the electrical energy that is absorbed by the bulb over a period of five minutes.
Fall 2015, Practice quiz, Problem #1
Answer: 180 J
22
The current flowing through an element is given in the plot below.
Calculate the total charge that passes through the element between t = 10 s and t = 15 s .
i  mA 
i
v
Fall 2015, Practice quiz, Problem #2
Answer: 125 mC
23
In the circuit given, determine the energy absorbed by the current source
over a period of 6 seconds.
Fall 2015, Quiz #1, Problem #1
Answer: 240 J
24
The current in a lightning thunderbolt is 3 104 A , and its duration is 120 ms.
The voltage between the clouds and the ground is 5 108 V .
Determine the total charge transmitted to the earth.
Fall 2015, Quiz #1, Problem #2
Answer: 3.6 kC
25