Download AP Physics Daily Problem #140

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AP Physics Daily Problem #131
A particle containing 20C of charge is fired northward at 10m/s into a region occupied
by a 2T magnetic field directed downward. You may neglect gravity.
Determine the force exerted on the particle (magnitude and direction)
Determine the magnitude and direction of an electric field that could be created in the
same region to cause the particle to continue in a straight line.
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AP Physics Daily Problem #132 (1977 #3)
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P2
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Electron
An electron is accelerated from rest through a potential difference of magnitude V
between infinite parallel plates P1 and P2. The electron then passes into a region of
uniform magnetic field strength B which exists everywhere to the right of plate P2. The
magnetic field is directed into the page.
(a) On the diagram above, clearly indicate the direction of the electric field between the
plates.
(b) In terms of V and the electron’s mass and charge, determine the electron’s speed at
plate P2.
(c) Describe in detail the motion of the electron through the magnetic field, and explain
why the electron moves this way.
(d) In terms of V, B, and the electron’s mass and charge, determine the work done on the
electron after it passes to the right of plate P2
(e) If the magnetic field remains unchanged, what could be done to cause the electron to
follow the straight-line path to the right of P2? Be specific in your answer
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Per
AP Physics Daily Problem #133 (1994 #4)
In a linear accelerator, protons are accelerated from rest through a potential difference to
a speed of approximately 3.1 x 106 meters per second. The resulting proton beam
produces a current of approximately 2 x 10-6ampere.
(a) Determine the potential difference through which the protons were accelerated.
(b) If the beam is stopped in a target, determine the amount of thermal energy that is
produced in the target in one minute.
Region of
Field B
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Proton Beam
Electron
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(Positive z
out of page)
The proton beam enters a region of uniform magnetic field B, as shown above, which
causes the beam to follow a semicircular path.
(c) Determine the magnitude of the field that is required to cause an arc of radius 0.10
meters.
(d) What is the direction of the magnetic field relative to the axes shown on the right?
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AP Physics Daily Problem #134
B
A square loop of wire, 30cm on each side, is free to rotate about the vertical axis shown.
A current of 5.0A flows through the wire in a clockwise direction. The loop is in a
uniform magnetic field of 2T directed from left to right. You may ignore the wires
leading into the loop.
(a) Determine the force on the leftmost side of the loop (magnitude and direction).
(b) Determine the force on the rightmost side of the loop (magnitude and direction).
(c) Determine the force on the top side of the loop (magnitude and direction).
(d) Determine the torque about the vertical axis (magnitude and direction).
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Per
AP Physics Daily Problem #135
B
N
wire
A horizontal wire is placed in a direction where it is perpendicular to the earth’s magnetic
field (55x10-6T) at the equator of the earth.
(a) Derive an equation to determine the current I needed to precisely negate the earth’s
magnetic field at a distance d above the wire.
(b) Using this equation, determine the current needed to negate the earth’s magnetic field
at a distance of 2m above the wire.
(c) At this current, what would be the magnetic field strength and direction at a location
2m below the wire?
(d) At this current, what would be the magnetic field strength and direction at a location
2m north of the wire?
Name
Per
AP Physics Daily Problem #136
A circular coil of wire, 30cm in diameter and containing
100 turns is placed in a magnetic field of 2T. The field is
decreased to a value of 1T over a time period of 5s.
(a) If the leads were connected, which way would current
flow in the loop?
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(b) What is the voltage between the leads?
(c) If a resistance of 4Ω is placed between the leads, what is the current that would flow
in the loop?
(d) If this process were repeated for an hour, how much energy would be dissipated by
the resistor?
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Per
AP Physics Daily Problem #137
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3m/s
5Ω
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A wire loop, 2meters by 4 meters, of negligible resistance is in the plane of the page with
its left end in a uniform 0.5-tesla magnetic field directed into the page, as shown above.
A 5-ohm resistor is connected between points X and Y. The field is zero outside the
region enclosed by the dashed lines. The loop is pulled to the right with a constant
velocity of 3 meters per second. Make all determinations for the time that the left end of
the loop is still in the field, and points X and Y are not in the field.
(a) Determine the potential difference induced between points X and Y.
(b) On the figure above, show the direction of the current induced in the resistor.
(c) Determine the force required to keep the loop moving at 3 meters per second
(d) Determine the rate at which work must be done to keep the loop moving at 3 meters
per second.
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AP Physics Daily Problem #138 (1994 #6)
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Rail
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Rod
A force F is applied
to
that therod slides with constant speed v over
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 a conducting
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rod so 
a frictionless pair of parallel conducting rails that are separated by a distance l. The rod
and rails have negligible resistance, but the rails are connected by a resistance R, as
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field Bperpendicular to and directed out of
shown above. Thereis a uniform
magnetic
the plane of the paper.
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(a) What is the direction of the induced current through the resistor?
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Determine expressions for the following in terms of v, B, l, and R
(b) The induced emf in the rod.
(c) The electric field in the rod
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(d) The magnitude
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(e) The power dissipated in the resistor as the rod moves in the magnetic field
(f) The magnitude of the external force F applied to the rod to keep it moving with
constant speed v.
Name
Per
AP Physics Daily Problem #139
200m/s
60m
An airplane is flying directly over the magnetic south pole of the earth. It has a speed of
200m/s and a wingspan of 60m. The earth’s magnetic field is about 55x10-6T
(a) What is the rate at which the aircraft cuts the magnetic flux?
(b) What is the induced emf from one wingtip to the other?
(c) Which wingtip (right or left as you face forward in the airplane) will be positive?
Explain your reasoning.
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Per
AP Physics Daily Problem #140
1/4λ
a. The optimum length for one type of receiving antenna is ¼ wavelength long.
How long would this antenna be to receive a radio station on a frequency of
97.1MHz?
b. How long would the antenna be to receive an AM radio station on a frequency of
1070kHz?
c. How long would the antenna be to receive a cellular phone transmission on a
frequency of 2.4GHz?