Download 1.67 10 m = × 12.0sin(120 ) V t =

PHY 102 Exam #2
Problem
1
2
3
4
Total
Instructions:
1.
2.
3.
4.
5.
Name ____________ ______________
Points
8
11
18
13
50
Score
Do all of your work in this booklet.
Show all of your steps in problems for full credit.
Be clear and neat in your work. Any illegible work, or
scribbling in the margins, will not be graded.
Place your answers in a box.
If you need more space, you may use the back of the
page and write On back in the problem space.
1. Multiple choice (8 pts) Find the answer which best fits the
question and write it in the space provided.
a. Two long parallel wires have current moving in opposite
directions but perpendicular to your paper. The force on the left
wire points
a) to the left. b) to the right. c) downward. d) none of these.
_____
b. In a transformer the voltage in the secondary coil is greater
than that in the primary coil. This is
a) a step-up transformer; b) a step-down transformer;
c) a gobot transformer d) an efficient transformer
e) none of these.
_____
c. The earth's magnetic field is parallel to the earth's surface at
a) the North Pole; b) the South Pole; c) the equator;
d) Wilmington, NC, e) none of these.
_____
d. The impedance has units of
a) farads; b) hertz; c) ohms; d) henries e) none of these
_____
e. If the B-field points out of your paper and a negative charge
moves from right to left in this field, then the force is directed
a) towards the bottom; b) out of the paper; c) into the
paper; d) to the left; e) none of these.
_____
f. An inductor stores
a) electrical energy; b) magnetic energy;
c) thermal energy; d) no energy; e) none of these.
_____
g. In a capacitive circuit the voltage _________ the current.
a) leads;
b) is in phase with;
c) lags
_____
h. A current carrying wire is perpendicular to your paper with the
current going into the paper from above. The magnetic field
produced looks like
a) a uniform field directed from left to right; b) a uniform
field directed from right to left; c) concentric circles
directed counterclockwise in the plane of the paper;
d) concentric circles directed clockwise in the plane of the
paper; e) none of these.
_____
___________________________________________________
.  10 31 kg mp  1.67 1026 kg
Constants me  911
2. Definitions/Principles (11 pts)
a. Write the exact expression for the:
(i) the magnetic field inside a solenoid,
(ii) the maximum emf generated by a loop rotating in a magnetic
field,
(iii) the inductive reactance.
b. A voltage source of V  12.0sin(120t ) is connected to a 3.0 
resistor. Find the
(i) Frequency of the voltage source:
____________
(ii) Measured current across the resistor:
____________
c. Indicate the direction of the magnetic field at the center of the
solenoid.
d. What is the path of the electron?
_________________________________________________
Bonus: An LC circuit has a capacitance of 1.5 F and an
inductance of 3.0 mH. What is the resonant frequency of this
circuit?
PHY 102 Exam #2
Name ____________ ______________
3. Problems (18 pts)
a. On the same bar of iron are wound two coils, one with 45 loops
and the other with 15 loops. If a 100.0 V alternating voltage is
connected to the 45 loop coil, what will be the voltage in the 15
loop coil?
4. Problems (13 pts)
a. A series LRC circuit includes a resistance of 150 an
inductive reactance of 337 and a capacitive reactance of
293. The rms current in the circuit is 0.233 A. What is the
rms voltage of the generator?
b. An ionized deuteron (a particle with a +1 charge) passes
through a velocity selector with fields of magnitude 40 mT and
8.0 kV/m. Find the speed of the ion.
b. In the last part, determine the phase difference and state if the
current leads or lags the voltage.
c. A magnetic field perpendicular to the plane of a wire loop with
and area of 0.40 m2 decreases by 0.20 T in 10-3 s. What is the
magnitude of the average value of the emf induced in the loop?
c. A 1.0 m long conducting rod is moving perpendicular to a
0.35 T magnetic field. How fast must the rod move in order to
produce and emf of 12 V across the ends?
d. A proton moves at a speed of 6 106 m/s perpendicular to a
constant magnetic field. The path is a circle of radius
1.3 103 m. What is the magnitude of the magnetic field?
d. What voltage is needed to create a current of 29.0 A in a circuit
containing only a 0.565 mF capacitor, when the frequency of
the source is 2.60 kHz?
e. In the figures below indicate the direction (left or right) of the
induced current along the path between points a and b.
e. An electric power line carries a current of 1400 A in a location
where the earth's magnetic field is 0.5 G. The line makes an
angle of 75o with respect to the field. What is the magnitude of
the magnetic force on a 120 m length of line?
__________
(when switch closed)
f. What is the current in a long, straight wire if the magnetic
field 1.00 mm from the wire is 2.00 102 T?
__________
__________