COIL EXAM QUESTIONS WITH VERIFIED
ANSWERS 3 VERSIONS Comprehensive Exam Bank:
Multiple Choice Questions
1. What is the unit of measurement for inductance?
A) Ohm
B) Farad
C) Henry
D) Siemens
Correct Answer: C) Henry
Rationale: The henry is the SI unit for inductance. Self-inductance is
measured in henries, named after Joseph Henry .
2. Mutual inductance between two magnetically coupled coils depends
on which factors?
A) Permeability of the core material only
B) Number of turns of the coils only
C) Cross-sectional area of their common core only
D) All of the above
Correct Answer: D) All of the above
Rationale: Mutual inductance between two magnetically coupled coils
depends on the permeability of the core material, number of turns of the
coils, and the cross-sectional area of their common core .
3. A choke coil works on the principle of:
A) Capacitance
,B) Resistance
C) Inductance
D) Conductance
Correct Answer: C) Inductance
Rationale: A choke coil operates on the principle of inductance. It is designed
to impede the flow of alternating current while allowing direct current to pass
.
4. What is the back emf induced in a coil when current changes from 1
A to zero in 1 ms, given the self-inductance is 4 H?
A) 1 V
B) 2 V
C) 3 V
D) 4 V
Correct Answer: D) 4 V
Rationale: The back emf induced in a coil is given by E = L × ΔI/Δt. With
L=4H, ΔI=1A, Δt=1ms=0.001s, E = 4 × 1/0.001 = 4 V .
5. The mutual inductance of a pair of coils is 0.75 H. If the current in
the primary coil changes from 0.5 A to 0 in 0.01 s, what is the average
induced emf in the secondary coil?
A) 37.5 V
B) 75 V
C) 0.0375 V
D) 7.5 V
,Correct Answer: A) 37.5 V
Rationale: Using the formula E = M × ΔI/Δt, E = 0.75 × (0.5/0.01) = 0.75 ×
50 = 37.5 V .
6. What is a "waste spark" ignition system?
A) A system where spark is wasted when the engine is off
B) A distributorless system where one coil fires two cylinders simultaneously
C) A system that wastes battery power
D) A system with multiple coils per cylinder
Correct Answer: B) A distributorless system where one coil fires two
cylinders simultaneously
Rationale: In a waste spark system, one coil pack serves two cylinders. One
spark fires on the compression stroke and the other fires on the exhaust
stroke, which is called the "waste spark" .
7. Which code range indicates ignition coil circuit problems in OBD-II
diagnostics?
A) P0100 to P0104
B) P0300 to P0304
C) P0351 to P0358
D) P0400 to P0404
Correct Answer: C) P0351 to P0358
Rationale: Diagnostic trouble codes P0351 through P0358 indicate circuit
problems relating to ignition coils. These codes point to specific coil circuit
faults .
, 8. What is the typical primary winding resistance specification for an
ignition coil?
A) 0.77 to 0.95 ohms
B) 10.3 to 13.9 ohms
C) 100 to 200 ohms
D) 1,000 to 2,000 ohms
Correct Answer: A) 0.77 to 0.95 ohms
Rationale: The standard value for primary coil resistance is 0.77 - 0.95 ohm.
The secondary coil resistance is much higher at 10.3 - 13.9 k-ohm .
9. What is the typical secondary winding resistance specification for an
ignition coil?
A) 0.77 to 0.95 ohms
B) 10.3 to 13.9 k-ohms
C) 100 to 200 ohms
D) 1,000 to 2,000 ohms
Correct Answer: B) 10.3 to 13.9 k-ohms
Rationale: The secondary coil resistance standard value is 10.3 - 13.9 k-ohm.
This is significantly higher than the primary resistance .
10. What is a common sign of a failing ignition coil?
A) Improved fuel economy
B) Engine misfires
C) Smoother idle
D) Increased power
ANSWERS 3 VERSIONS Comprehensive Exam Bank:
Multiple Choice Questions
1. What is the unit of measurement for inductance?
A) Ohm
B) Farad
C) Henry
D) Siemens
Correct Answer: C) Henry
Rationale: The henry is the SI unit for inductance. Self-inductance is
measured in henries, named after Joseph Henry .
2. Mutual inductance between two magnetically coupled coils depends
on which factors?
A) Permeability of the core material only
B) Number of turns of the coils only
C) Cross-sectional area of their common core only
D) All of the above
Correct Answer: D) All of the above
Rationale: Mutual inductance between two magnetically coupled coils
depends on the permeability of the core material, number of turns of the
coils, and the cross-sectional area of their common core .
3. A choke coil works on the principle of:
A) Capacitance
,B) Resistance
C) Inductance
D) Conductance
Correct Answer: C) Inductance
Rationale: A choke coil operates on the principle of inductance. It is designed
to impede the flow of alternating current while allowing direct current to pass
.
4. What is the back emf induced in a coil when current changes from 1
A to zero in 1 ms, given the self-inductance is 4 H?
A) 1 V
B) 2 V
C) 3 V
D) 4 V
Correct Answer: D) 4 V
Rationale: The back emf induced in a coil is given by E = L × ΔI/Δt. With
L=4H, ΔI=1A, Δt=1ms=0.001s, E = 4 × 1/0.001 = 4 V .
5. The mutual inductance of a pair of coils is 0.75 H. If the current in
the primary coil changes from 0.5 A to 0 in 0.01 s, what is the average
induced emf in the secondary coil?
A) 37.5 V
B) 75 V
C) 0.0375 V
D) 7.5 V
,Correct Answer: A) 37.5 V
Rationale: Using the formula E = M × ΔI/Δt, E = 0.75 × (0.5/0.01) = 0.75 ×
50 = 37.5 V .
6. What is a "waste spark" ignition system?
A) A system where spark is wasted when the engine is off
B) A distributorless system where one coil fires two cylinders simultaneously
C) A system that wastes battery power
D) A system with multiple coils per cylinder
Correct Answer: B) A distributorless system where one coil fires two
cylinders simultaneously
Rationale: In a waste spark system, one coil pack serves two cylinders. One
spark fires on the compression stroke and the other fires on the exhaust
stroke, which is called the "waste spark" .
7. Which code range indicates ignition coil circuit problems in OBD-II
diagnostics?
A) P0100 to P0104
B) P0300 to P0304
C) P0351 to P0358
D) P0400 to P0404
Correct Answer: C) P0351 to P0358
Rationale: Diagnostic trouble codes P0351 through P0358 indicate circuit
problems relating to ignition coils. These codes point to specific coil circuit
faults .
, 8. What is the typical primary winding resistance specification for an
ignition coil?
A) 0.77 to 0.95 ohms
B) 10.3 to 13.9 ohms
C) 100 to 200 ohms
D) 1,000 to 2,000 ohms
Correct Answer: A) 0.77 to 0.95 ohms
Rationale: The standard value for primary coil resistance is 0.77 - 0.95 ohm.
The secondary coil resistance is much higher at 10.3 - 13.9 k-ohm .
9. What is the typical secondary winding resistance specification for an
ignition coil?
A) 0.77 to 0.95 ohms
B) 10.3 to 13.9 k-ohms
C) 100 to 200 ohms
D) 1,000 to 2,000 ohms
Correct Answer: B) 10.3 to 13.9 k-ohms
Rationale: The secondary coil resistance standard value is 10.3 - 13.9 k-ohm.
This is significantly higher than the primary resistance .
10. What is a common sign of a failing ignition coil?
A) Improved fuel economy
B) Engine misfires
C) Smoother idle
D) Increased power
