BASIC ELECTRICITY REVIEWER
1. Which of the following elements of electrical engineering cannot be analyzed using Ohm’s law?
a) Capacitors
b) Inductors
c) Transistors
d) Resistance
Answer: c
Explanation: Ohm’s law cannot be used for unilateral networks as such networks only allow current
flow in one direction. Transistor forms a unilateral network. Thus, Ohm’s law cannot be used on
Transistors.
2. What is constant for a charged spherical shell according to basic electrical energy?
a) Electrical potential outside the spherical shell
b) Electrical potential inside the spherical shell
c) Electrical field outside the spherical shell
d) Electrical field inside the spherical shell
Answer: b
Explanation: According to principles of electrical energy, the electrical potential inside the spherical
shell is constant and is represented as V = kq/R where k = 1/4πεo. This potential is the same as that of
the potential on the surface of the sphere.
3. Where does electro-static shielding occur in a charged spherical shell?
a) When electrical potential outside spherical shell is zero
b) When electrical potential inside the spherical shell is zero
c) When electrical field outside the spherical shell
d) Electrical field inside the spherical shell
Answer: d
Explanation: The electrical field inside the spherical shell is zero and this is basically known as
electrostatic shielding. The electric field outside the sphere is inversely proportional to the square of
the radius.
4. Which of the following is a correct representation of peak value in an AC Circuit?
a) RMS value/Peak factor
b) RMS value*Form factor
c) RMS value/Form factor
d) RMS value*Peak factor
Answer: d
Explanation: A peak factor in an AC circuit represents the ratio of the peak value to the RMS value.
The peak factor also called the crest factor indicates how extreme the peaks are present in a
waveform.
5. Which of the following according to fundamentals of electrical energy is incorrect about alternating
current?
a) Frequency is zero
b) Magnitude changes with time
c) Can be transported to larger distances with less loss in power
d) Flows in both directions
Answer: a
Explanation: An alternating current changes its value with time and flows in both directions. The loss
in power is less due to alternating current properties and thus, can be transported to larger distances.
6. How many cycles will an AC signal make in 2 seconds if its frequency is 100 Hz?
a) 50
b) 100
c) 150
d) 200
Answer: d
Explanation: In electrical engineering, the frequency represents the ratio of the number of cycles to
the total time. Since frequency is given as 100 Hz and the time is 2 sec thus a total of 200 cycles will
be made.
7. What will be the direction of the drift velocity of electrons change with respect to the electric field?
a) same as that of electric field
b) opposite to that of electric field
c) perpendicular to that of the electric field in a positive direction
d) perpendicular to that of the electric field in a negative direction
Answer: b
Explanation: Basically drift velocity can be said to be the average velocity obtained by the free
electrons in metal when an electric field is applied. The direction of drift velocity for the electrons
present in metal will be opposite to that of the applied electric field.
8. What will be the current density of metal if a current of 30A is passed through a cross-sectional
area of 0.5m2?
a) 7.5 A/m2
b) 15 A/m2
c) 60 A/m2
d) 120 A/m2
Answer: c
Explanation: Current density is the ratio of the current flowing in a cross-sectional area. If a current of
30A is passed through a cross-sectional area of 0.5m2.
9. Which of the following is correct about the power consumed by R1 and R2 connected in series if
the value of R1 is greater than R2?
a) R1 will consume more power
b) R2 will consume more power
c) R1 and R2 will consume the same power
d) The relationship between the power consumed cannot be established
Answer: a
Explanation: In the electrical engineering introduction it is explained that the power can be expressed
as P = I2*R. When two resistors are connected in series the current flowing through the resistors is
the same and thus, power consumed by the larger resistor will be more.
10. What is zero for a charged spherical shell?
a) Electrical potential outside the spherical shell
b) Electrical potential inside the spherical shell
c) Electrical field outside the spherical shell
d) Electrical field inside the spherical shell
Answer: d
Explanation: According to the fundamentals of the electrical field inside the spherical shell is zero and
this is known as electrostatic shielding. The electric field outside the sphere is inversely proportional
to the square of the radius.
11. What kind of quantity is an Electric potential?
a) Vector quantity
b) Tensor quantity
c) Scalar quantity
d) Dimensionless quantity
Answer: c
Explanation: Electric potential refers to the work done to bring a unit positive charge from a point
with higher potential to a point with lower potential. Since electric potential only has magnitude but
no direction, it is a scalar quantity.
12. What do crowded lines of force indicate?
a) Strong electric field
b) Weak electric field
c) Strong electric potential
d) Weak electric potential
Answer: a
Explanation: According to the principles of electric fields, when crowded lines of field are present the
electric fields are very strong. The strong electric field can be witnessed near the poles of a magnet as
the lines of force are crowded in this region.
13. What is the direction of the electric field at a point?
a) Along the line perpendicular to the electric field
b) Along the line tangent to the electric field
c) Electric field has no direction
d) Electric field has a random direction
Answer: b
Explanation: According to the basics of the Electric field, it is a vector quantity and has a direction. The
direction of the electric field is said to be along the line tangent to the electric field.
14. What is the magnitude of mutually induced emf, E2 in a transformer?
a) directly proportional to rate of change of flux and number of secondary turns
b) inversely proportional to rate of change of flux and number of secondary turns
c) proportional to rate of change of flux and inversely proportional to number of secondary turns
d) inversely proportional to the rate of change of flux and proportional to number of secondary turns
Answer: a
Explanation: Due to the supply voltage, a secondary induced emf is produced. V1 is in antiphase with
E2 and the magnitude of E2 is proportional to rate of change of flux and number of secondary turns.
15. Which of the following will happen in a transformer when the number of secondary turns is less
than the number of primary turns?
a) The voltage gets stepped up
b The voltage gets stepped down
c) The power gets stepped up
d) The power gets stepped down
Answer: b
Explanation: The voltage transformation ratio is basically the ratio of the number of secondary turns
to that of the number of primary turns. When the transformation ratio is less than 1, the step-down
operation occurs.
16. What is the number of primary turns in a 200/1000 V transformer if the emf per turn is 10V?
a) 5
b) 10
c) 20
d) 40
Answer: c
Explanation: The number of primary turns is the ratio of induced emf in the primary to the emf
induced per turn. Thus, the number of primary turns in a 200/1000 V transformer with emf per turn
of 10V is 200/10 = 20.
17. Which of the following is a correct representation of average value in an AC Circuit?
a) RMS value/Form factor
b) RMS value*Form factor
c) RMS value/Peak factor
d) RMS value*Peak factor
Answer: a
Explanation: The form factor basically gives the expression for DC of equal power to a given AC. A
form factor in an AC circuit represents the ratio of the RMS value to the average value. Thus, average
value = RMS value/Form factor.
18. Who defined electric current and devised a method to measure current?
a) Michael Faraday
b) Andre-Marie Ampere
c) Nikola Tesla
d) Alessandro Antonio Volta
Answer: b
Explanation: Andre-Marie Ampere is a French physicist and mathematician who defined electric
current and devised a method to measure current in the 1820s.
19. How many electrons will constitute 2 Coulombs of electric charge?
a) 6.24 * 1018 electrons
b) 12.48 * 1018 electrons
c) 1.602 * 1019 electrons
d) 3.204 * 1019 electrons
Answer: b
Explanation: One Coulomb of charge consists of 1/(1.602*10-19) electron that is 6.24 * 1018
electrons. A coulomb is a unit for the charge. Thus, for 2 Coulombs of charge will have 6.24 * 1018 * 2
= 12.48 * 1018 electrons.
20. Which of the following is correct about direct current?
a) Magnitude is constant
b) Frequency is zero
c) Can be transported to larger distances with less loss in power
d) Flows in one direction
Answer: c
Explanation: A direct current has a fixed value and does not change with time. The frequency of the
direct current is equal to zero as it does not change with time.
21. Who witnessed the effect of magnetism for the first time?
a) Hans Christian Orsted
b) Alexander Graham Bell
c) Michael Faraday
d) Gustav Robert Kirchhoff
Answer: a
Explanation: Hans Christian Orsted was a Danish physicist and chemist who witnessed the effect of
magnetism for the first time. He discovered that electric current can create a magnetic field using an
experiment.
22. Which of the following according is correct about electrical conductivity?
a) It is the ratio of current density to the electric field
b) It is the product of current density and electric field
c) It is the ratio of the electric field to current density
d) It is the reciprocal of the product of current density and electric field
Answer: a
Explanation: Electrical conductivity gives the ability of a conductor to conduct electric current. The
point form of Ohm’s law says that the electrical conductivity (σ) is the ratio of current density (J) to
electric field (E).
23. What is responsible for the current to flow?
a) Protons
b) Electrons
c) Nucleus
d) Protons and Electrons
Answer: b
Explanation: For the current to flow in a circuit electrons are required. Electrons are negatively
charged and when the potential difference is applied these electrons flow to constitute a current. The
current direction is opposite to the electron flow.
24. Which of the following according to KCL must be zero?
a) Algebraic sum of currents in closed-loop
b) Algebraic sum of power in closed-loop
c) Algebraic sum of currents entering and leaving a junction
d) Algebraic sum of voltages across the input and output
Answer: c
Explanation: KCL or Kirchhoff’s current law helps in finding the currents flowing in the circuit. KCL
states that the current entering a junction is equal to the current leaving a junction.
25. How many directions can the electric field at a point have?
a) Zero
b) One
c) Two
d) Many
Answer: b
Explanation: Electric field is a vector quantity and has a direction. The direction of the electric field is
said to be along the line tangent to the electric field. Thus, the electric field at a point has one
direction.
26. Which of the following will happen in a transformer when the number of secondary turns is
greater than the number of primary turns?
a) The voltage gets stepped up
b) The voltage gets stepped down
c) The power gets stepped up
d) The power gets stepped down
Answer: a
Explanation: The voltage transformation ratio is the ratio of the number of secondary turns to that of
the number of primary turns. When the transformation ratio is greater than 1, the step-up operation
occurs.
27. Which of the following is correct about the voltage transformation ratio in electrical engineering?
a) Ratio of number of primary turns to the number of secondary turns
b) Ratio of induced emf in secondary to induced emf in primary
c) Ratio of secondary current to the primary current
d) Ratio of power in primary to power in secondary
Answer: b
Explanation: The voltage transformation ratio is the ratio of the number of secondary turns to the
number of primary turns. This can also be expressed as the ratio of induced emf in secondary to
induced emf in primary or ratio of primary current to secondary current.
28. Which of the following according to the fundamentals of electrical engineering is correct about
the induced emf in primary of transformer?
a) It is the ratio of primary turns to emf induced per turn
b) It is the product of primary turns and emf induced per turn
c) It is the ratio of secondary turns to emf induced per turn
d) It is the product of secondary turns and emf induced per turn
Answer: b
Explanation: The number of primary turns is the ratio of induced emf in the primary to the emf
induced per turn. Thus, the induced emf in the primary of the transformer is the product of primary
turns and emf induced per turn.
29. Which of the following current is drawn by the primary circuit of an ideal transformer when the
secondary is open?
a) Secondary current
b) Leakage current
c) Magnetizing current
d) Working on current
Answer: c
Explanation: When the secondary is open no current flows through the load, thus no secondary
current is drawn. The primary coil for an ideal transformer is purely inductive and thus, only draws
magnetizing current.
30. What does positive power in an electrical element indicate?
a) Element is absorbing power
b) Element is supplying power
c) Element may absorb or supply power
d) Element is neither absorbing nor supplying power
Answer: a
Explanation: Power in an electrical element is the product of voltage and current. Positive power will
be established when both voltage and current are positive or both are negative. Positive power will
indicate that the element is absorbing power.
31. How does induce emf in DC motor react to supply voltage?
a) It will aid the supply voltage
b) It will be double the supply voltage
c) It will oppose the supply voltage
d) It will be half of the supply voltage
Answer: c
Explanation: Lenz’s law suggests that the direction of induced emf is such that it opposes the cause.
The supply voltage will be the cause in this case. Thus induced emf will oppose the supply voltage.
32. Which of the following type of circuits in electrical engineering cannot be analyzed using Ohm’s
law?
a) Unilateral
b) Bilateral
c) Linear
d) Conductors
Answer: a
Explanation: Ohm’s law cannot be used for analyzing unilateral networks as such networks only allow
current flow in one direction. A unilateral network can consist diode, transistor, etc.
33. Which of the following according to KVL must be zero?
a) Algebraic sum of currents in closed-loop
b) Algebraic sum of power in closed-loop
c) Algebraic sum of losses in closed-loop
d) Algebraic sum of voltages in closed-loop
Answer: d
Explanation: KVL or Kirchhoff’s voltage law proves the law of conservation of energy around a closed
path. KVL can be used in the circuit to find the circuit parameters by considering that the algebraic
sum of voltages in a closed loop is zero.
34. What is the unit of electrical resistance?
A) Ohm (Ω)
B) Volt (V)
C) Ampere (A)
D) Watt (W)
Answer: A) Ohm (Ω)
35. Which law states that current is directly proportional to voltage and inversely proportional to
resistance?
A) Newton’s Law
B) Ohm’s Law
C) Faraday’s Law
D) Coulomb’s Law
Answer: B) Ohm’s Law
36. What is the formula for electric power?
A) P = VI
B) P = V/R
C) P = IR
D) P = V + I
Answer: A) P = VI
37. The SI unit of electric current is:
A) Volt
B) Ohm
C) Ampere
D) Watt
Answer: C) Ampere
38. Which device is used to measure electric current?
A) Voltmeter
B) Ammeter
C) Ohmmeter
D) Wattmeter
Answer: B) Ammeter
39. What is the charge of one electron?
A) +1.6 x 10^-19 C
B) -1.6 x 10^-19 C
C) +1.6 x 10^19 C
D) -1.6 x 10^19 C
Answer: B) -1.6 x 10^-19 C
40. In a series circuit, the current is:
A) Same through all components
B) Different through each component
C) Zero
D) Infinite
Answer: A) Same through all components
41. The resistance of a conductor depends on:
A) Length and cross-sectional area
B) Temperature only
C) Voltage
D) Current
Answer: A) Length and cross-sectional area
42. What is the purpose of a fuse in an electric circuit?
A) To increase current
B) To protect the circuit from overcurrent
C) To reduce voltage
D) To store energy
Answer: B) To protect the circuit from overcurrent
43. If voltage across a resistor is doubled, the current through it will:
A) Double
B) Halve
C) Remain the same
D) Become zero
Answer: A) Double
44. The unit of electric power is:
A) Joule
B) Watt
C) Coulomb
D) Volt
Answer: B) Watt
45. Electric power is a:
A) Vector quantity
B) Scalar quantity
C) Both A and B
D) None of these
Answer: B) Scalar quantity
46. Which of the following is an active device?
A) Battery
B) Resistor
C) Capacitor
D) Inductor
Answer: A) Battery
47. What is the current flowing through a 10 Ω resistor connected to a 20 V supply?
A) 0.5 A
B) 2 A
C) 10 A
D) 200 A
Answer: B) 2 A
48. The energy consumed by a 100 W bulb in 5 hours is:
A) 100 Wh
B) 200 Wh
C) 500 Wh
D) 50 Wh
Answer: C) 500 Wh
49. Which of the following materials is a good conductor of electricity?
A) Copper
B) Rubber
C) Glass
D) Plastic
Answer: A) Copper
50. The device that converts electrical energy into mechanical energy is called:
A) Generator
B) Transformer
C) Motor
D) Battery
Answer: C) Motor
51. The voltage across a 5 Ω resistor carrying 3 A current is:
A) 15 V
B) 8 V
C) 5 V
D) 3 V
Answer: A) 15 V
52. Which law is used to analyze complex circuits with multiple loops?
A) Ohm’s Law
B) Kirchhoff’s Laws
C) Coulomb’s Law
D) Faraday’s Law
Answer: B) Kirchhoff’s Laws
53. The power consumed by a device is 60 W when connected to 120 V. The current drawn is:
A) 0.5 A
B) 2 A
C) 60 A
D) 180 A
Answer: A) 0.5 A
54. The equivalent resistance of two resistors 4 Ω and 6 Ω connected in series is:
A) 2.4 Ω
B) 10 Ω
C) 1.5 Ω
D) 24 Ω
Answer: B) 10 Ω
55. The equivalent resistance of two resistors 4 Ω and 6 Ω connected in parallel is:
A) 2.4 Ω
B) 10 Ω
C) 1.5 Ω
D) 24 Ω
Answer: A) 2.4 Ω
56. Which of the following is true for an ideal transformer?
A) Power input = Power output
B) Voltage input = Voltage output
C) Current input = Current output
D) Resistance input = Resistance output
Answer: A) Power input = Power output
57. The unit of electric charge is:
A) Ampere
B) Coulomb
C) Volt
D) Watt
Answer: B) Coulomb
58. A device that stores electrical energy in an electric field is called:
A) Resistor
B) Capacitor
C) Inductor
D) Transformer
Answer: B) Capacitor
59. The flow of electric charge is called:
A) Voltage
B) Current
C) Resistance
D) Power
Answer: B) Current
60. Which scientist is credited with defining electric current and its measurement?
A) Michael Faraday
B) Andre-Marie Ampere
C) Nikola Tesla
D) Alessandro Volta
Answer: B) Andre-Marie Ampere
61. What happens to power if resistance is increased while voltage remains constant?
A) Power increases
B) Power decreases
C) Power remains the same
D) Power becomes zero
Answer: B) Power decreases
62. The formula for electric energy consumption is:
A) E = P × t
B) E = V × I
C) E = I × R
D) E = V / I
Answer: A) E = P × t
63. Which of the following is NOT a unit of power?
A) Watt
B) Horsepower
C) Joule
D) Kilowatt
Answer: C) Joule