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Unformatted text preview: Don’s Boot Camp for Midterm 1
These are problems to help you prepare for midterm 1 UB
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3 1. The ampliﬁcation or gain of a transistor ampliﬁer may depend on the temperature. The
gain for a certain ampliﬁer at room temperature ( 20.0◦ C ) is 30.0, where as at 55.0◦ C it
is 35.2. What would be the gain at 30.0◦ C if the gains depends linearly, over a limited
range?
2. To measure temperatures, physicists and astronomers often use the variation of intensity
of electromagnetic radiation emitted by an object. The wavelength λmax at which the
intensity is greatest is given by the equation λmax T = 0.2898cm K, where T is the object
temperature in Kelvins. In 1965, microwave radiation peaking at λmax = 0.107cm was
discovered coming in all directions from space. To which temperature does this correspond?
What was the 1978 Nobel Prize in Physics give for? What was the 2006 Nobel Prize in
Physics give for?
3. In the interval between the freezing point of water and 700.0◦ C, a platinum resistance
thermometer is used for interpolating the temperatures on the international scale. The
Celsius temperature TC is given by a formula for resistance R with temperature
R = R0 (1 + ATC + BTC 2 ) where A and B are constants determined by measurements at the ice point of water, the
steam point of water, and the melting point of zinc ( 419.514◦ C ). (a) If R equals 10.000
ohms at the ice point, 13.946 ohms at the steam point, and 24.174 ohms at the melting
point of zinc, ﬁnd R0 , A, and B; (b) Plot R versus TC in the range from 0◦ C to 700.0◦ C. 4. The length of a mercury column of a thermometer is 4.0 cm long when immersed in ice
water and 24 cm long when immersed in boiling water. (a) What would be the length at
22◦ C? (b) When immersed in a solution the length is 25.4 cm. What is the temperature
of the solution?
5. A cubic metal box with sides of length 20 cm contains air at pressure of 1 atm and
a temperature of 300K. The box is sealed so that the volume is constant and heated to
400K. What is the net force on each side of the box? 6. A 1 km steel railroad rail is fastened securely at both ends when the temperature is
20◦ C. With increasing temperature the rail begins to buckle. Assuming the buckle is
triangular, how high is the buckle at 25◦ C? Ph For these problems 711 use the following constants:
αaluminum = 2.8×10−5 K −1 , αsteel = 1.3×10−5 K −1 , αbrass = 1.9×10−5 K −1 , Yaluminum =
8 × 1010 P a, Ysteel = 21 × 1010 P a 7. A composite bar of length L = L1 + L2 is made from a bar of material 1 and length L1
attached to a bar of material 2 and length L2 , as shown.
(a) Show the eﬀective coeﬃcient of linear expansion is
α= (α1 L1 + α2 L2 )
.
L (b) Using steel and brass, design such a composite bar whose length is 52.4 cm and
whose eﬀective coeﬃcient of linear expansion is 16.0 × 10−6 K −1 .
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material 2 material 1 L 8. A thick aluminum rod and thin steel wire is attached in parallel, as shown. The
temperature is 12.0◦ C. Both the rod and wire are 95.0cm long and neither is under stress.
The system is heated to 100◦ C. Calculate the resulting stress in the wire, assuming that
the rod expands freely. wire aluminum rod Ph 9. A steel ball is 4.000cm in diameter at 28◦ C. A brass ring has an interior diameter of
2.992cm at 30◦ C. At what common temperature will the ball just slide through the ring? 10. a) The inner diameter of a steel ring is 2.0000 cm, and the diameter of an aluminum
disk is 2.0100 cm. Both are at 430◦ C. At what common temperature will the disk ﬁt
precisely into the hole in the steel ring?
b) If after the aluminum disk is ﬁtted precisely into the hole the two metals are the
temperature is changed to 200 C, what is the stress in the steel ring? 11. A grandfather’s clock is calibrated at a temperature of 20◦ C. The pendulum is a thin
brass rod with a heavy mass attached to the end. On a hot day, when the temperature is
30◦ C does the clock “run” fast or slow? How much time does it gain or lose in a 7 day
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This note was uploaded on 11/12/2010 for the course PHYS 153 PHYS 153 taught by Professor Sarahburke,donaldwitt,michaeldhasinoff,andrzejkotlicki during the Spring '10 term at The University of British Columbia.
 Spring '10
 SarahBurke,DonaldWitt,MichaelDHasinoff,AndrzejKotlicki

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