Download Physics 102 Second Major Exam (942) - ( 13 problems)

Physics 102 Second Major Exam (942) -
( 13 problems) - 28 May, 1995
Q1. A monatomic ideal gas undergoes the process shown in the figure,
i.e. the system begins in state A and ends in state C.
Calculate the change in the internal energy of the gas.
Al-Shukri.P102.942.ex2
P ( kPa )C.
480 -
180 -
C
B
A

6x10-3
V(m3)

12x10-3
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Q2. A monatomic ideal gas is initially at a pressure of 101 kPa in a cylinder of volume 2.25x10 -3 m3 and in equilibrium with
Its surroundings at 300 K. The gas is then adiabatically compressed to a final volume of 1.65x10-3 m3 and held at this
volume. (a) Find the temperature and pressure of this gas at the moment the volume reaches 1.65x10 -3 m3. (b) What
must be the temperature and pressure of this gas when it returns again to thermal equilibrium with its surroundings ?
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Q3. One kilogram of water at 0 oC is heated to 62o C. Calculate the change in its entropy.
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Q4. An ideal ( i.e. Carnot ) heat pump is used to pump heat from the outside air at T = - 5o C into a house which is at 25o C.
How much work is required to pump 1000 J of heat into the house?
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Q5. An electron is placed at each corner of an equilateral triangle having sides 20 cm long.
Y
See the figure. (a) What is the magnitude and direction of the electric field at the origin, O?
(b) What is the magnitude and direction of the force on an electron placed at the origin ?
X
o
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Q6. A uniform electric field exists in a region between two oppositely charged plates. An electron is released from rest at the
surface of the negatively charged plate and strikes the surface of the opposite plate 2.0 cm away, in a time 1.5x10-8 s. (a) What
is the speed of the electron as it strikes the second plate ? (b) What is the magnitude of the electric field between the plates?
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Q7. Consider a very long insulating cylinder of radius R with a uniform volume charge density ρ .
(a) What is the magnitude of the electric field at points far from the ends and inside the cylinder ( r < R )?
(b) What is the electric field outside the cylinder ( r > R ) ?
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Q8. A solid conducting cylinder has a charge of 10 µC. Inside the cylinder
10 µC
a −3 µC charge rests at the centre of a hollow spherical space, as shown in
the figure. (a) What is the charge on the surface of the hollow spherical space ?
—3 µC
(b) What is the charge on the surface of the cylinder ?
Hollow spherical
space
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Q9. A sphere with a charge of 4x10-9 C and mass of 5.0 g is suspended by means of a light thread
between two large parallel plates 7.0 cm apart. The thread makes an angle of 30o with the
vertical ( see the figure ). (a) Draw a free body diagram for the forces acting on the charged
sphere (b) What should be the potential difference between the two plates so that
30°
the sphere will be in equilibrium in this position ?
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Q10. At a certain distance from a point charge, the electric field intensity is 500 volts/m and the potential is -3000 volts.
What is the sign a nd magnitude of the point charge ?
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Q11.
In the circuit shown, C1 = 2 µF, C2 = 4 µF and C3 = 6 µF.
The potential applied is Vab = 24 V. Calculate
(a) the charge on each capacitor, and
(b) the potential difference between a and b ( i.e. Va - Vb ).
a+
b–
C1
C2
C3
d
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Q12. A 4-µF capacitor is charged to 200 V. It is then connected across
an uncharged 6-µF capacitor, as shown in the figure.
(a) Find the charge on each capacitor .
(b) Find the potential across each capacitor.
4-µF
6-µF
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Q13. Suppose that you wish to install a heating coil that will convert electrical energy to heat at a rate of 300 W with a
current of 1.5 A. If the resistivity of the coil is 10-6 Ω.m and its diameter is 0.3 mm, Determine its resistance and length.