Solutions Manual: Fundamentals of Electric Circuits,
7th Edition by Charles K. Alexander & Matthew N.O.
Sadiku – with Complete Solutions
CHAPTER 1: BASIC CONCEPTS (Questions 1-30)
Question 1:
Which of the following is the SI unit of electric charge?
A) Ampere
B) Volt
C) Coulomb
D) Watt
*Rationale: * The coulomb (C) is the SI unit of electric charge, defined as the charge
transported by a constant current of one ampere in one second. One coulomb is
equivalent to approximately 6.24 × 10^18 elementary charges .
Question 2:
What is the SI unit of electric current?
,A) Coulomb
B) Volt
C) Ampere
D) Ohm
*Rationale: * The ampere (A) is the SI unit of electric current, representing the flow of one
coulomb of charge per second. It is one of the seven base SI units .
Question 3:
A current of 5 amperes flowing for 10 seconds transfers how much charge?
A) 2 C
B) 15 C
C) 50 C
D) 0.5 C
*Rationale: * Charge (Q) equals current (I) multiplied by time (t): Q = I × t = 5 A × 10 s =
50 C. This is the fundamental relationship between current, charge, and time.
Question 4:
The voltage across a resistor is 12 V and the current through it is 3 A. What is the
resistance?
A) 36 Ω
B) 15 Ω
C) 4 Ω
D) 0.25 Ω
*Rationale: * Using Ohm's Law, R = V/I = 12 V / 3 A = 4 Ω. This is the foundational
relationship for circuit analysis.
Question 5:
Power absorbed by a resistor can be calculated using which formula?
,A) P = I²R
B) P = V²/R
C) P = VI
D) All of the above
*Rationale: * All three formulas are equivalent for resistors. Using Ohm's Law (V = IR), we
can derive P = VI = I²R = V²/R. These are all valid expressions for power dissipated in a
resistor.
Question 6:
A 100 W light bulb is connected to a 120 V source. What current does it draw?
A) 1.2 A
B) 0.83 A
C) 0.833 A
D) 12 A
*Rationale: * Using P = VI, I = P/V = 100 W / 120 V ≈ 0.833 A. This demonstrates the
practical application of power calculations.
Question 7:
What is the power absorbed by a resistor with resistance 10 Ω when a current of 2 A
flows through it?
A) 20 W
B) 10 W
C) 5 W
D) 40 W
*Rationale: * Using P = I²R = (2 A)² × 10 Ω = 4 × 10 = 40 W. The power is proportional
to the square of the current.
, Question 8:
If the voltage across an element is 8 V and the current entering the positive terminal is 2
A, what is the power?
A) 16 W (absorbed)
B) 16 W (supplied)
C) 4 W
D) 6 W
*Rationale: * When current enters the positive terminal of an element, the element
absorbs power. P = VI = 8 V × 2 A = 16 W absorbed .
Question 9:
If the voltage across an element is 8 V and the current leaves the positive terminal
(negative current entering positive terminal), what is the power?
A) -16 W (supplied)
B) 16 W (absorbed)
C) 4 W
D) -4 W
*Rationale: * When current flows out of the positive terminal, the element supplies power.
The power is negative when using passive sign convention: P = VI = 8 V × (-2 A) = -16 W,
indicating power is being supplied .
Question 10:
Which of the following is NOT a passive element?
A) Resistor
B) Capacitor
C) Inductor
D) Voltage source
*Rationale: * Resistors, capacitors, and inductors are passive elements that absorb or store
energy. Voltage and current sources are active elements that supply energy to the circuit.
7th Edition by Charles K. Alexander & Matthew N.O.
Sadiku – with Complete Solutions
CHAPTER 1: BASIC CONCEPTS (Questions 1-30)
Question 1:
Which of the following is the SI unit of electric charge?
A) Ampere
B) Volt
C) Coulomb
D) Watt
*Rationale: * The coulomb (C) is the SI unit of electric charge, defined as the charge
transported by a constant current of one ampere in one second. One coulomb is
equivalent to approximately 6.24 × 10^18 elementary charges .
Question 2:
What is the SI unit of electric current?
,A) Coulomb
B) Volt
C) Ampere
D) Ohm
*Rationale: * The ampere (A) is the SI unit of electric current, representing the flow of one
coulomb of charge per second. It is one of the seven base SI units .
Question 3:
A current of 5 amperes flowing for 10 seconds transfers how much charge?
A) 2 C
B) 15 C
C) 50 C
D) 0.5 C
*Rationale: * Charge (Q) equals current (I) multiplied by time (t): Q = I × t = 5 A × 10 s =
50 C. This is the fundamental relationship between current, charge, and time.
Question 4:
The voltage across a resistor is 12 V and the current through it is 3 A. What is the
resistance?
A) 36 Ω
B) 15 Ω
C) 4 Ω
D) 0.25 Ω
*Rationale: * Using Ohm's Law, R = V/I = 12 V / 3 A = 4 Ω. This is the foundational
relationship for circuit analysis.
Question 5:
Power absorbed by a resistor can be calculated using which formula?
,A) P = I²R
B) P = V²/R
C) P = VI
D) All of the above
*Rationale: * All three formulas are equivalent for resistors. Using Ohm's Law (V = IR), we
can derive P = VI = I²R = V²/R. These are all valid expressions for power dissipated in a
resistor.
Question 6:
A 100 W light bulb is connected to a 120 V source. What current does it draw?
A) 1.2 A
B) 0.83 A
C) 0.833 A
D) 12 A
*Rationale: * Using P = VI, I = P/V = 100 W / 120 V ≈ 0.833 A. This demonstrates the
practical application of power calculations.
Question 7:
What is the power absorbed by a resistor with resistance 10 Ω when a current of 2 A
flows through it?
A) 20 W
B) 10 W
C) 5 W
D) 40 W
*Rationale: * Using P = I²R = (2 A)² × 10 Ω = 4 × 10 = 40 W. The power is proportional
to the square of the current.
, Question 8:
If the voltage across an element is 8 V and the current entering the positive terminal is 2
A, what is the power?
A) 16 W (absorbed)
B) 16 W (supplied)
C) 4 W
D) 6 W
*Rationale: * When current enters the positive terminal of an element, the element
absorbs power. P = VI = 8 V × 2 A = 16 W absorbed .
Question 9:
If the voltage across an element is 8 V and the current leaves the positive terminal
(negative current entering positive terminal), what is the power?
A) -16 W (supplied)
B) 16 W (absorbed)
C) 4 W
D) -4 W
*Rationale: * When current flows out of the positive terminal, the element supplies power.
The power is negative when using passive sign convention: P = VI = 8 V × (-2 A) = -16 W,
indicating power is being supplied .
Question 10:
Which of the following is NOT a passive element?
A) Resistor
B) Capacitor
C) Inductor
D) Voltage source
*Rationale: * Resistors, capacitors, and inductors are passive elements that absorb or store
energy. Voltage and current sources are active elements that supply energy to the circuit.
