QUESTIONS FOR FINAL EXAM OF PHYSICS A1
A. MULTI CHOICE QUESTIONS:
1) Charge is distributed uniformly on the surface of a large flat plate. The electric field 2 cm
from the plate is 30N/C. The electric field 4 cm from the plate is:
A. 120N/C
B. 80N/C
C. 30N/C
D. 15N/C
E. 7.5N/C
2) Electric field lines:
A. are trajectories of a test charge
B. are vectors in the direction of the electric field
C. form closed loops
D. cross each other in the region between two point charges
E. are none of the above
3) An isolated charged point particle produces an electric field with magnitude E at a point 2m
away. At a point 1m from the particle the magnitude of the field is:
A. E
B. 2E
C. 4E
D. E/2
E. E/4
This and the next question refer to the following situation.
4) A solid sphere of radius R = 5 cm is made of non-conducting material and carries a total
negative charge Q = -12 C. The charge is uniformly distributed throughout the interior of the
sphere.
What is the magnitude of the electric potential V at a
distance r = 30 cm from the center of the sphere,
given that the potential is zero at r = ∞ ?
(a) V = -7.20 × 1010 V
(b) V = -3.60 × 1011 V
(c) V = -1.20 × 1012 V
(d) V = -2.16 × 1012 V
(e) V = -4.32 × 1013 V
5) What is the magnitude of the electric field E at a distance r = 2 cm from the center of the
sphere?
(a) E = 3.06 × 1012 N/C
(b) E = 5.40 × 1012 N/C
(c) E = 1.73 × 1013 N/C
(d) E = 4.32 × 1013 N/C
(e) E = 2.70 × 1014 N/C
6) A thin rubber rod is charged with a linear charge density λ > 0, then shaped into an arc of
angle 60° and radius R. The electric field magnitude at its center is:
7)
8) The potential associated with an electric field is defined by.
The field is then:
9) There is an ideal gas in a closed container.
If the temperature of the gas is doubled without changing its volume, the average number of gas
molecules striking a wall of the container per unit time is
(a) √2 times as large as that before the temperature is doubled.
(b) 1/√2 times as large as that before the temperature is doubled.
(c) the same as before the temperature is doubled.
(d) twice as large as that before the temperature is doubled.
(e) 1/2 times as large as that before the temperature is doubled.
This and the next question refer to the following situation
10) Five moles of oxygen gas initially have pressure p = 50 kPa and volume V = 0.25 m3.
What is the initial temperature Ti of the gas?
(a) Ti = 250 K
(b)
(c)
(d)
(e)
Ti = 301 K
Ti = 503 K
Ti = 1204 K
Ti = 1505 K
11) The oxygen expands adiabatically and quasistatically to V = 0.75 m3. Its final equilibrium
temperature becomes Tf. What is the ratio Tf /Ti?
(a) Tf /Ti = 0.333
(b) Tf /Ti = 0.481
(c) Tf /Ti = 0.644
(d) Tf /Ti = 0.735
(e) Tf /Ti = 0.887
12) During a reversible adiabatic expansion of an ideal gas, which of the following is NOT true?
A. pV γ = constant B. pV = nRT
C. TV γ−1 = constant D. pV = constant
13) The latent heat of the water-steam phase transition at p=1 atm and T=100oC is 2256 kJ/kg.
What is the entropy change S as the liquid vaporizes?
(a) –22.56 kJ/K-kg
(b) -6048 J/K-kg
(c) 0 J/K-kg
(d) 6048 J/K-kg
(e) 22.56 kJ/K-kg
14) An ideal monoatomic gas has a temperature of 350 K at a pressure of 1.5 atm.
What is the density of the gas?
(a) 0.05 mol/l
(b) 1 mol/l
(c) 6.2 mol/l
(d) 15.7 mol/l
(e) Not enough information is given.
15) Give circle current with a radius R and current I. Magnetic induction B of this current
creating in its center is equal:.
16) Two infinitely long straight currents which are parallel and have opposite dicrections will:
a) attract each other
b) does not interact with each other.
c) repel each other.
d) repulsive force is greater than atractive force.
17) An α particle has a charge q = +2 e, mass m = 6,64.10-27 kg moving with kinetic energy of
500 eV, perpendicular to the magnetic fields with B = 0.1 T. Cycle of rotation of particles
equals:
18)
This and the next question refer to the following situation.
Two cylindrical conductors each carry current I into the screen as shown. The conductor on the
left is solid and has radius R=3a. The conductor on the right has a hole in the middle and carries
current only between R=a and R=3a.
I
I
a
3
a
3a
2
a
19) What is the relation between the magnetic field at R = 2a for the two cases (L=left,
R=right)?
(a) BL(2a)< BR(2a)
(b) BL(2a)= BR(2a)
(c) BL(2a)> BR(2a)
20) What is the relation between the magnetic field at R = 6a for the two cases (L = left, R =
right)?
(a) BL(6a)< BR(6a)
(b) BL(6a)= BR(6a)
(c) BL(6a)> BR(6a)
ANSWERS
1)A
2)E
6)A
7)A
11)C
12)D
16)C
17)B
3)C
4)B
5)C
8)C
9)E
10)B
13)D
14)A
15)B
18)C
19)B
20)C
B. PROBLEMS:
1) Three identical point charges q are placed at three vertices of a square of side a. Calculate
the electric potential energy of the system.
3) 1 mole of an ideal gas follows the cycle shown in the figure 3. 1-2 is isochoric process,
2-3 is adiabatic process and 3-1 is isobaric process. V1, V2, P1, P2 are given.
Determine:
a) Adiabatic coefficient  and molar specific heats Cv
2
P2
and Cp (from the process 2-3) ?
b) The heats from 1-2 and 3-1 processes ?
c) The thermal efficiency of the engine operating with
this cycle.
3
P1
1
.
3) A heat engine makes use of the thermal cycle shown. The
working fluid is 3 grams of nitrogen, an ideal diatomic gas.
There are two isobaric and two isochoric processes:
p1 = 1×106 Pa, p2 = 2×106 Pa
V1 = 500 cm3, V2 = 1000 cm3.
3.1) What is the temperature, T, of the gas at point 4 (p1, V1)?
3.2) How much work, Wby, does the gas do in the 1→2 process?
3.3) How much work, Wby, does the gas do in the 2→3 process?
V1
Figure 3
V2