WERABE UNIVERSITY
COLLEGE OF NATURAL AND COMPUTATIONAL SCIENCE
DEPARTMENT OF PHYSICS
Electromagnetism (Phys 2002)
Final Exam for Chemistry second year students
Time Allowed: 1 Hours
Maximum Mark: 𝟓𝟎%
Name ……………………………………………… ID. No……………
Instructions
1. Be sure that you have written your ID. No and Name.
2. This exam contains five parts.
3. Your Answer Should be Clear and Precise.
4. Do not spend too much time on any one question.
5. There will be a strict penalty for any misbehavior observed during examination.
6. Except scientific calculator no need of any electronic devices (switch off your mobile).
Identify the choice that best completes the statement or answers the question. Write your
answer in the space provided.
1. _______ A parallel plate capacitor has an area of 1000 𝑐𝑚2 and a distance of
1𝑐𝑚. A new dielectric material is inserted and its new capacitance
value is calculated to be 1.77 𝑥 10−10 F. What must be the value of the
dielectric constant κ ?
A. 0.75
B.
1.5
C.
2
D.
2.25
2. _______ Three resistors are connected between points a and b as shown in the figure
below.
The effective resistance of the circuit is
A.
1𝜴
B. 11 𝜴
C.
1 k𝜴
D.
11 k𝜴
3. _______ The charge of 20.0 𝜇𝐶 is stored on the capacitor when a potential difference
between its two parallel plates is 200.0 𝑉, what is the capacitance of the capacitor?
A. 1.0 𝜇𝐹
10.0 𝜇𝐹
B.
C. 0.1 𝜇𝐹
4.0 𝑚𝐹
D.
4. _______ An air filled parallel plate capacitor is connected to a potential difference v to
store electric charge. If the area of the plates is A and the separation between the plates is
d, then the electrical energy stored on the capacitor is
1 𝜀0 𝑑𝑉 2
A.
2
𝐴
B.
𝜀0𝐴𝑉2
𝑑
C.
𝜀0𝑑𝑉2
𝐴
D.
1 𝜀0 𝐴𝑉 2
2
𝑑
5. _______ Kirchhoff”s junction rule is a consequence of conservation of
A. Mass
B.
Momentum
C.
Electrical energy
D.
Charge
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6. _______ Four resistors are connected to a voltage source as shown in the circuit diagram
shown below
What are the current through the 3 Ω resistor and the voltage drop across the 4 Ω resistor,
respectively?
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A. 2 A and 4 𝑉
B.
2
3
𝐴 and 4 𝑉
C.
3
4
𝐴 and 8 𝑉
D.
4
3
𝐴 and 8 𝑉
7. _______ Four capacitors are connected in a capacitor network as shown in the figure
below.
The equivalent capacitance between terminals a and b in 𝜇F is
A. 4
B. ¼
C. ¾
D. 12
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8. ______________ All of the following wires are made of the same material but are
different sizes. Identify the wire with the lowest resistance.
9. ______________ The charge for a parallel plate capacitor is determined to be
450 𝑥 10−6 𝐶. It is charged with a source of V = 110V. What is the
energy stored on the capacitor?
A. 0.02475 J
B. 0.0495 J
C. 0.2475 J
D. 0.495 J
10. ______________ A wire of length L and cross-sectional area A has a resistivity ρ. Which
of the following formulas can be used to calculate the resistance of the
wire?
𝜌𝐿
A. 𝑅 = 𝐴
B.
𝜌𝐴
𝑅= 𝐿
C.
𝐿
𝑅 = 𝜌𝐴
D.
𝐴
𝑅 = 𝜌𝐿
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11. ______________ Two resistors 𝑅1 = 6𝛺 and 𝑅2 = 12𝛺 are connected in parallel to
each other and in series to 𝑅3 = 2𝛺 as shown in figure below. What is
the net resistance in the circuit?
A. 1𝛺
B.
3𝛺
C.
6𝛺
D.
2𝛺
12. _______ The capacitance of a parallel-plate capacitor depends on which of the
following?
I. The plate area
II. The plate separation
III. The voltage of the capacitor
A. II only
B. III only
C. II and III only
D.
I and II only
13. _______ If the sheet of a Bakelite is inserted between the plates of an air capacitor, the
capacitance will
A. Decrease
C. remain unchanged
B. Increase
D. become zero
14. _______ If three 15 µF Capacitors are connected in series, the net capacitance is
A. 5 µF
C. 45 µF
B. 30 µF
D. 50 µF
15. _______ A dielectric material must be
A. Resistor
B. Insulator
C. good conductor
D. Semi conductor
16. _______ A parallel plate condenser with oil between the plates (dielectric constant of oil
K = 2) has a capacitance C. If the oil is removed, then capacitance of the capacitor
becomes
A. √2 𝐶
B. 2C
C.
𝐶
√2
𝐶
D. 2
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17. _______ What is the total capacitance in the given circuit?
A. 7 F
B. 13 F
C. 4.3 F
D. 16 F
18. _______ What effect will be on the capacitance of a capacitor when the area of the
parallel plate capacitor is decreased?
A. It will increase
C. It will decrease
B. There will be no effect
D. It will initially increase and then decrease
19. _______ What happens to the potential difference between the capacitors parallel plates
as the distance between parallel plates halved?
A. Decreased
B. Increased
C. Remains constant
D. All
20. _______ Which of the following options are incorrect? C is the capacitance of the
capacitor, V is the voltage and Q is the charge of the capacitor.
A. Energy stored in the capacitor is 0.5 CV2
B. Energy stored in the capacitor is 0.5 QV
C. Charge stored in the capacitor is CV
D. The capacitance equivalent when C1, C2, C3, ……….., Cn capacitors are connected in
series: 𝐶1 + 𝐶2 + 𝐶3 + ⋯ … … + 𝐶𝑛
21. _______ In a nonuniform electric field, electric dipole experiences
A. Torque only
B. Torque as well as net force
C. Force only
D. None of these
22. _______ What is the SI unit of electric current?
A. Volt
B. Watt
C. Ohm
D. Ampere
23. _______ The current density in a conductor is defined as:
A. Current per unit volume
B. Current per unit area
B. Current per unit length
D. Resistance per unit area
24. _______ If the current in a conductor is doubled, what happens to the current density?
A. It remains the same B. It doubles
C. It halves
D. It quadruples
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25. _______ The drift velocity of electrons in a conductor is:
A. Directly proportional to the current
B. Inversely proportional to the current
C. Independent of the current
D. Directly proportional to the electric field
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Answer Key Phys 2031
1. _______
2. ________
3. _________
4. _________
5. _________
6. ________
7. _________
8. _________
9. _________
10. ________
11. _________
12. __________
13. _________
14. _________
15. ________
16. _________
17. __________
18. __________
19. ________
20. ________
21. _______
22. _________
23. _________
24. _________
25. _________
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