Solutions Manual for Fundamentals of Electric
Circuits, 7th Edition by Charles K. Alexander
FUNDAMENTALS OF ELECTRIC CIRCUITS, 7TH EDITION
200+ ORIGINAL EXAM QUESTIONS
Alexander & Sadiku – Full 19 Chapters Coverage
Answers + Detailed Solutions
CHAPTER 1: BASIC CONCEPTS
QUESTION 1
The charge flowing through a device is q(t) = 3t² + 2t + 1 coulombs. What is the
current at t = 2 seconds?
A) 10 A
B) 12 A
C) 14 A
D) 16 A
1
,Correct Answer: C
Solution: i(t) = dq/dt = 6t + 2. At t = 2, i = 6(2) + 2 = 14 A.
QUESTION 2
Find the charge q(t) flowing through a device if the current is i(t) = 3A and q(0) =
1C.
A) q(t) = 3t + 1 C
B) q(t) = 3t C
C) q(t) = 3t² + 1 C
D) q(t) = 3 + t C
Correct Answer: A
Solution: q(t) = ∫i(t)dt + q(0) = ∫3dt + 1 = 3t + 1 C [citation:3].
QUESTION 3
A current of 5A flows for 3 minutes. How much charge is transferred?
2
,A) 15 C
B) 60 C
C) 90 C
D) 900 C
Correct Answer: D
Solution: q = i × t = 5 × (3 × 60) = 5 × 180 = 900 C.
QUESTION 4
A 1.2-kW toaster operates for 4 minutes each day for 30 days. Find the energy cost
if electricity costs 9 cents per kWh.
A) $0.054
B) $0.216
C) $0.432
D) $0.864
Correct Answer: B
Solution: Energy = 1.2 kW × (4/60) h × 30 = 2.4 kWh. Cost = 2.4 × $0.09 = $0.216
[citation:3].
3
, QUESTION 5
A circuit has three elements with powers p₁ = -205 W, p₂ = 60 W, and p₃ = 45 W.
What is p₃?
A) -100 W
B) 100 W
C) 205 W
D) 310 W
Correct Answer: B
Solution: By conservation of power, the sum of powers in a circuit must equal
zero. Therefore, p₃ = 100 W [citation:3].
QUESTION 6
How many coulombs are represented by 6.24 × 10¹⁸ electrons?
A) 0.5 C
4
Circuits, 7th Edition by Charles K. Alexander
FUNDAMENTALS OF ELECTRIC CIRCUITS, 7TH EDITION
200+ ORIGINAL EXAM QUESTIONS
Alexander & Sadiku – Full 19 Chapters Coverage
Answers + Detailed Solutions
CHAPTER 1: BASIC CONCEPTS
QUESTION 1
The charge flowing through a device is q(t) = 3t² + 2t + 1 coulombs. What is the
current at t = 2 seconds?
A) 10 A
B) 12 A
C) 14 A
D) 16 A
1
,Correct Answer: C
Solution: i(t) = dq/dt = 6t + 2. At t = 2, i = 6(2) + 2 = 14 A.
QUESTION 2
Find the charge q(t) flowing through a device if the current is i(t) = 3A and q(0) =
1C.
A) q(t) = 3t + 1 C
B) q(t) = 3t C
C) q(t) = 3t² + 1 C
D) q(t) = 3 + t C
Correct Answer: A
Solution: q(t) = ∫i(t)dt + q(0) = ∫3dt + 1 = 3t + 1 C [citation:3].
QUESTION 3
A current of 5A flows for 3 minutes. How much charge is transferred?
2
,A) 15 C
B) 60 C
C) 90 C
D) 900 C
Correct Answer: D
Solution: q = i × t = 5 × (3 × 60) = 5 × 180 = 900 C.
QUESTION 4
A 1.2-kW toaster operates for 4 minutes each day for 30 days. Find the energy cost
if electricity costs 9 cents per kWh.
A) $0.054
B) $0.216
C) $0.432
D) $0.864
Correct Answer: B
Solution: Energy = 1.2 kW × (4/60) h × 30 = 2.4 kWh. Cost = 2.4 × $0.09 = $0.216
[citation:3].
3
, QUESTION 5
A circuit has three elements with powers p₁ = -205 W, p₂ = 60 W, and p₃ = 45 W.
What is p₃?
A) -100 W
B) 100 W
C) 205 W
D) 310 W
Correct Answer: B
Solution: By conservation of power, the sum of powers in a circuit must equal
zero. Therefore, p₃ = 100 W [citation:3].
QUESTION 6
How many coulombs are represented by 6.24 × 10¹⁸ electrons?
A) 0.5 C
4
