Sirindhorn International Institute of Technology
Thammasat University at Rangsit
School of Information, Computer and Communication Technology
SCS 139: Problem Set 1
Due date: Feb 8, 2013 (Friday)
1. [Halliday, Resnick, and Walker, 9E, P28.4]
2. [Halliday, Resnick, and Walker, 9E, P28.21]
3. [Halliday, Resnick, and Walker, 9E, P28.28]
4. [Halliday, Resnick, and Walker, 9E, P28.40]
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SCS139 HW1
Monday, January 28, 2013
9:46 PM
SCS139 HW Page 1
SCS139 HW Page 2
SCS 139 Dr.Prapun: Problem Set 2
Due date: Feb 15, 2013 (Friday)
1. [HRW, 9E, Q29.12] In Figure 1, two long straight wires at separation d = 16.0 cm carry
currents i1= 3.61 mA and i2 = 3.00i1 out of the page. (a) Where on the x axis is the net
magnetic field equal to zero? (b) If the two currents are doubled, is the zero-field point
shifted toward wire 1, shifted toward wire 2, or unchanged?
Figure 1: [HRW, 9E, Fig. 29-42]
2. [HRW, 9E, P29.15] Figure 2 shows two current segments. The lower segment carries a
current of i1= 0.40 A and includes a semicircular arc with radius 5.0 cm,angle 180°, and
center point P. The upper segment carries current i2 = 2i1 and includes a circular arc with
radius 4.0 cm, angle 120°, and the same center point P. What are the (a) magnitude and (b)
direction of the net magnetic field B at P for the indicated current directions? What are the
(c) magnitude and (d) direction of if i1is reversed?
Figure 2: [HRW, 9E, Fig. 29-44]
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3. [HRW, 9E, P29.36] In Figure 3, five long parallel wires in an xy plane are separated by
distance d = 8.00 cm, have lengths of 10.0 m, and carry identical currents of 3.00 A out of
the page. Each wire experiences a magnetic force due to the other wires. In unit-vector
notation, what is the net magnetic force on (a) wire 1, (b) wire 2, (c) wire 3, (d) wire 4, and
(e) wire 5?
Figure 3: [HRW, 9E, Fig. 29-63]
4. [HRW, 9E, P29.46] Eight wires cut the page perpendicularly at the points shown in Figure 4.
A wire labeled with the integer k (k = 1, 2, . . . , 8) carries the current ki, where i = 4.50 mA.
For those wires with odd k, the current is out of the page; for those with even k, it is into
the page. Evaluate
 B  ds
along the closed path in the direction shown.
Figure 4: [HRW, 9E, Fig. 29-69]
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SCS139 HW2
Saturday, February 02, 2013
10:20 PM
SCS139 HW Page 1
SCS139 HW Page 2
SCS139 HW Page 3
SCS 139 Dr.Prapun: Problem Set 3
Due date: Feb 22, 2013 (Friday)
1. [HRW, 9E, P29.52] A solenoid 1.30 m long and 2.60 cm in diameter carries a current of 18.0
A. The magnetic field inside the solenoid is 23.0 mT. Find the length of the wire forming the
solenoid.
2. [HRW, 9E, P30.2] A certain elastic conducting material is stretched into a circular loop of
12.0 cm radius. It is placed with its plane perpendicular to a uniform 0.800 T magnetic field.
When released, the radius of the loop starts to shrink at an instantaneous rate of 75.0 cm/s.
What emf is induced in the loop at that instant?
3. [HRW, 9E, P30.4] A wire loop of radius 12 cm and resistance 8.5 is located in a uniform
magnetic field B that changes in magnitude as given inFigure 1. The vertical axis scale is set
by Bs = 0.50 T, and the horizontal axis scale is set by ts = 6.00 s. The loop’s plane is
perpendicular to B . What emf is induced in the loop during time intervals (a) 0 to 2.0 s, (b)
2.0 s to 4.0 s, and (c) 4.0 s to 6.0 s?
Figure 1: [HRW, 9E, Fig. 30-33]
4. [HRW, 9E, P30.54] In Figure 2, = 100 V, R1 = 10.0, R2 = 20.0, R3 = 30.0, and L = 2.00
H. Immediately after switch S is closed, what are (a) i1 and (b) i2? (Let currents in the
indicated directions have positive values and currents in the opposite directions have
negative values.) A long time later, what are (c) i1 and (d) i2? The switch is then reopened.
Just then, what are (e) i1 and (f) i2? A long time later, what are (g) i1 and (h) i2?
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Figure 2: [HRW, 9E, Fig. 30-60]
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SCS139 HW3
Friday, February 15, 2013
2:02 PM
SCS139 HW Page 1
SCS139 HW Page 2
SCS139 HW Page 3
SCS139 HW Page 4
SCS 139 Dr.Prapun: Problem Set 4
Due date: None
1. A current through an element in a circuit can be described by
i  t   8cos  500 t  25
a.
b.
c.
d.
A
What is the amplitude of the current?
What is its angular frequency?
Find the frequency of the current.
Calculate is at t = 2 ms.
Hint: None of these are correct: 7.25, 7.93, 6.939, -4.405, -7.93, -3.622, 7.425
2. Express the following signals in their standard forms.
a. v(t) = 21 cos(4t-15o) V
b. i(t) = -8 sin(10t+70o) mA
c. v(t) = 120 sin (10t –50o ) V
d. i(t) = -60cos(30t +10o) mA
3. [HRW, 9E, P33.1] A certain helium–neon laser emits red light in a narrow band of
wavelengths centered at 632.8 nm and with a “wavelength width” of 0.0100 nm. What is
the corresponding “frequency width” for the emission?
4. [HRW, 9E, P33.12] In a plane radio wave the maximum value of the electric field component
is 5.00 V/m. Calculate the maximum value of the magnetic field component.
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SCS139 HW4
Tuesday, February 19, 2013
2:06 PM
SCS139 HW Page 1
SCS139 HW Page 2