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PHY 102 CHAPTER 6 CBT EXAMINATION
Conductors, Semiconductors, Insulators, Charge Carriers, Electric Current, Resistance and Ohm's Law
1.
Materials are generally classified into:
A. Solids, liquids and gases
B. Conductors, semiconductors and insulators
C. Elements, compounds and mixtures
D. Metals, liquids and gases
Answer: B
2.
A material that allows electric current to flow easily is called:
A. Insulator
B. Semiconductor
C. Conductor
D. Dielectric
Answer: C
3.
Which of the following is a conductor?
A. Glass
B. Rubber
C. Copper
D. Plastic
Answer: C
4.
A material that opposes the flow of electric current is called:
A. Conductor
B. Semiconductor
C. Insulator
D. Electrolyte
Answer: C
5.
Which of the following is an insulator?
A. Copper
B. Aluminium
C. Rubber
D. Silver
Answer: C
6.
A semiconductor is a material whose conductivity is:
A. Very high
B. Very low
C. Between that of a conductor and an insulator
D. Infinite
Answer: C
7.
Which of the following is a semiconductor?
A. Copper
B. Silicon
C. Gold
D. Aluminium
Answer: B
8.
Another commonly used semiconductor is:
A. Iron
B. Zinc
C. Germanium
D. Silver
Answer: C
9.
The most widely used semiconductor material is:
A. Germanium
B. Copper
C. Silicon
D. Gold
Answer: C
10.
Charge carriers in metallic conductors are:
A. Protons
B. Neutrons
C. Free electrons
D. Ions
Answer: C
11.
Charge carriers in electrolytes are:
A. Free electrons
B. Ions
C. Neutrons
D. Protons
Answer: B
12.
Charge carriers in semiconductors are:
A. Protons and neutrons
B. Electrons and holes
C. Electrons only
D. Ions only
Answer: B
13.
Silicon has how many valence electrons?
A. 2
B. 3
C. 4
D. 5
Answer: C
14.
Germanium has how many valence electrons?
A. 2
B. 3
C. 4
D. 5
Answer: C
15.
Electric current is the:
A. Flow of resistance
B. Flow of voltage
C. Rate of flow of charge
D. Rate of flow of energy
Answer: C
16.
The symbol for electric current is:
A. R
B. V
C. I
D. Q
Answer: C
17.
The SI unit of electric current is:
A. Volt
B. Ohm
C. Coulomb
D. Ampere
Answer: D
18.
Current is given by:
A. V = IR
B. I = Q/t
C. P = IV
D. R = V/I
Answer: B
19.
One ampere is equal to:
A. One volt per second
B. One coulomb per second
C. One joule per second
D. One watt per second
Answer: B
20.
The charge of an electron is:
A. 1.6 × 10⁻¹⁹ C
B. 1.6 × 10¹⁹ C
C. 9.1 × 10⁻³¹ C
D. 6.02 × 10²³ C
Answer: A
21.
The conventional direction of current is:
A. Negative to positive
B. Positive to negative
C. Electron to proton
D. Random
Answer: B
22.
Current flowing in one direction only is:
A. AC
B. DC
C. Oscillating current
D. Alternating current
Answer: B
23.
DC stands for:
A. Dynamic Current
B. Direct Current
C. Differential Current
D. Distributed Current
Answer: B
24.
A battery supplies:
A. AC
B. DC
C. Both AC and DC
D. None
Answer: B
25.
Alternating current changes:
A. Resistance only
B. Voltage only
C. Magnitude and direction
D. Frequency only
Answer: C
26.
AC means:
A. Active Current
B. Alternating Current
C. Applied Current
D. Ampere Current
Answer: B
27.
The standard AC frequency in Nigeria is:
A. 25 Hz
B. 50 Hz
C. 75 Hz
D. 100 Hz
Answer: B
28.
The SI unit of resistance is:
A. Ampere
B. Volt
C. Ohm
D. Joule
Answer: C
29.
Resistance is represented by:
A. I
B. V
C. R
D. Q
Answer: C
30.
Ohm's law states that:
A. Current is directly proportional to voltage at constant temperature
B. Voltage is inversely proportional to current
C. Resistance is proportional to voltage
D. Power is proportional to current
Answer: A
31.
The mathematical expression for Ohm's law is:
A. P = IV
B. I = Q/t
C. V = IR
D. R = VI
Answer: C
32.
The SI unit of potential difference is:
A. Ohm
B. Volt
C. Joule
D. Coulomb
Answer: B
33.
An instrument used to measure electric current is:
A. Voltmeter
B. Ammeter
C. Ohmmeter
D. Wattmeter
Answer: B
34.
An ammeter is connected in:
A. Parallel
B. Series
C. Mixed
D. Shunt
Answer: B
35.
An instrument used to measure voltage is:
A. Ammeter
B. Ohmmeter
C. Voltmeter
D. Galvanometer
Answer: C
36.
A voltmeter is connected in:
A. Series
B. Parallel
C. Mixed
D. Shunt
Answer: B
37.
Resistance depends on:
A. Length of conductor
B. Cross-sectional area
C. Nature of material
D. All of the above
Answer: D
38.
Increasing the length of a conductor:
A. Decreases resistance
B. Increases resistance
C. Has no effect
D. Removes resistance
Answer: B
39.
Increasing the cross-sectional area of a conductor:
A. Increases resistance
B. Decreases resistance
C. Has no effect
D. Doubles voltage
Answer: B
40.
The resistance of a conductor is:
A. Directly proportional to its length
B. Inversely proportional to its length
C. Independent of length
D. Equal to voltage
Answer: A
41.
The resistance of a conductor is:
A. Directly proportional to area
B. Inversely proportional to area
C. Equal to area
D. Independent of area
Answer: B
42.
The relation between resistance and resistivity is:
A. R = ρL/A
B. R = AL/ρ
C. R = Aρ/L
D. R = ρ/A
Answer: A
43.
The symbol ρ represents:
A. Current
B. Resistance
C. Resistivity
D. Voltage
Answer: C
44.
The SI unit of resistivity is:
A. Ω
B. Ωm
C. A
D. V
Answer: B
45.
If V = 12 V and R = 4 Ω, calculate the current.
A. 2 A
B. 3 A
C. 4 A
D. 6 A
Answer: B
46.
If I = 5 A and R = 10 Ω, calculate the voltage.
A. 20 V
B. 30 V
C. 40 V
D. 50 V
Answer: D
47.
If V = 24 V and I = 6 A, calculate the resistance.
A. 2 Ω
B. 4 Ω
C. 6 Ω
D. 8 Ω
Answer: B
48.
1000 mA is equal to:
A. 0.1 A
B. 1 A
C. 10 A
D. 100 A
Answer: B
49.
1 kV is equal to:
A. 100 V
B. 1000 V
C. 10000 V
D. 10 V
Answer: B
50.
Electrical power is given by:
A. P = IV
B. P = IR
C. P = V/R
D. P = I/R
Answer: A
CHAPTER 6 FORMULAS
Electric Current
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Ohm's Law
Resistance of a Conductor
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Electrical Power
Electrical Energy
Symbols
I = Current (Ampere, A)
Q = Charge (Coulomb, C)
t = Time (s)
V = Potential Difference (Volt, V)
R = Resistance (Ohm, Ω)
ρ = Resistivity (Ωm)
L = Length of conductor (m)
A = Cross-sectional area (m²)
P = Power (Watt, W)
E = Electrical Energy (Joule, J)
This version integrates Conductors, Insulators, Semiconductors, Silicon, Germanium, Charge Carriers, Current, Resistance, and Ohm's Law into a single 1–50 CBT sheet for easy copying.