JOURNEYMAN ELECTRICIAN NEC 2026/2027 EXAM PREP | BONDING JUMPERS &
AC SYSTEMS | COMPREHENSIVE QUESTIONS AND VERIFIED ANSWERS | 100%
SUCCESS GUARANTEED
1. What is the primary purpose of bonding in an electrical system?
Bonding establishes a low-impedance path to facilitate the operation of
overcurrent protective devices (OCPDs) and reduce voltage differences
between conductive parts. Per NEC Article 250, bonding ensures electrical
continuity and capacity to safely conduct fault current.
2. What is the difference between bonding and grounding?
Grounding connects the electrical system to the earth (ground electrode),
while bonding connects metallic parts together and to the grounded
conductor. Bonding primarily protects people by limiting voltage differences;
grounding dissipates static charge and lightning energy.
3. Define 'bonding jumper' per NEC 2026 Article 100.
A bonding jumper is a reliable conductor that ensures the required electrical
conductivity between metal parts required to be electrically connected.
4. What is a Main Bonding Jumper (MBJ)?
The main bonding jumper (MBJ) is the connection between the grounded
circuit conductor (neutral) and the equipment grounding conductor (EGC) or
enclosure at the service. It is installed at the service entrance.
5. What is a System Bonding Jumper (SBJ)?
A system bonding jumper connects the grounded conductor to the supply-
side bonding jumper or the equipment grounding conductor, or both, at a
separately derived system (SDS). It performs the same function as the MBJ
but at an SDS.
6. Where is the main bonding jumper installed?
The MBJ is installed at the service disconnect enclosure, connecting the
neutral bus to the equipment grounding conductor or the enclosure itself. Per
NEC 250.24(B), it must be at each service disconnecting means.
7. What is a Supply-Side Bonding Jumper (SSBJ)?
A supply-side bonding jumper is a conductor installed on the supply side of a
service or separately derived system (SDS) to ensure the required electrical
Journeyman Electrician NEC 2026 Exam Prep — Bonding Jumpers & AC Systems | Page 1
, conductivity between metal parts required to be electrically connected.
Covered in NEC 250.102.
8. What is an Equipment Bonding Jumper (EBJ)?
An equipment bonding jumper is the connection between two or more
portions of the equipment grounding conductor. It ensures continuity of the
EGC path around intervening raceways, boxes, or enclosures.
9. How does NEC 2026 define a 'bonding conductor or jumper'?
NEC 2026 Article 100 defines it as a reliable conductor that ensures required
electrical conductivity between metal parts required to be electrically
connected. This includes both conductors and other conductive means (e.g.,
metal raceways used as EGCs).
10. What NEC article primarily covers grounding and bonding?
NEC Article 250 covers grounding and bonding. It includes requirements for
system grounding, equipment grounding, bonding conductors, and
grounding electrode systems.
11. What is the difference between a bonding jumper and a grounding
electrode conductor?
A bonding jumper connects metallic parts together for equipotential
purposes. A grounding electrode conductor (GEC) connects the electrical
system to the grounding electrode system (earth connection). They serve
different but complementary purposes.
12. What does NEC 250.4(A)(1) require regarding grounded systems?
NEC 250.4(A)(1) requires that electrical systems be grounded where they
can be grounded so that the maximum voltage to ground from ungrounded
conductors does not exceed 150 volts (for certain system voltages), to limit
voltage imposed by lightning or line surges.
13. What is 'effective ground-fault current path'?
An electrically conductive path from the point of a ground fault on a wiring
system through normally non-current-carrying conductors, equipment, and
the earth, if applicable, to the electrical supply source. Per NEC 250.4(A)(5),
it must be permanent, electrically continuous, with sufficient capacity to
conduct safely any fault current likely to be imposed on it.
14. What are the two types of bonding jumpers covered in NEC 250.102?
NEC 250.102 covers (1) Supply-side bonding jumpers (at the supply side of
service equipment or SDS), and (2) Equipment bonding jumpers (on the load
side connecting EGC paths).
Journeyman Electrician NEC 2026 Exam Prep — Bonding Jumpers & AC Systems | Page 2
,15. Can the neutral conductor serve as the EGC in a multi-wire branch
circuit?
No. The neutral (grounded) conductor can only serve as the EGC on the
supply side of the service point or SDS. On the load side of service
equipment, the neutral and EGC must be separate per NEC 250.142.
16. What is the function of bonding at a service?
Bonding at the service connects the grounded conductor (neutral), EGC, and
all non-current-carrying metal parts together and to the grounding electrode
system, ensuring a low-impedance fault-current path that allows OCPDs to
operate properly.
17. What is 'equipotential bonding'?
Equipotential bonding connects all conductive parts that may differ in
potential, ensuring they are at the same voltage. This reduces the risk of
electric shock from voltage differences. Common applications include
swimming pools and agricultural facilities.
18. Can a bonding jumper be a bare conductor?
Yes. Bonding jumpers may be bare, covered, or insulated conductors. NEC
250.119 requires EGCs to be identified by green or green with yellow stripe
coloring, or bare, when insulated.
19. What is the maximum length allowed for the main bonding jumper?
NEC does not impose a maximum length restriction on the MBJ, but it must
be installed within the service disconnect enclosure or between the service
disconnect and the grounded conductor connection. Practically, it should be
as short as possible.
20. What happens if the MBJ is omitted or improperly installed?
Without the MBJ, the neutral is not bonded to the EGC at the service, which
means the neutral will be floating relative to the equipment enclosure. This
can result in dangerous voltage on metal enclosures and OCPDs may fail to
operate during a fault.
SECTION 2: SIZING BONDING JUMPERS
21. How is the main bonding jumper sized?
Per NEC 250.28(D), the MBJ must not be smaller than specified in NEC
Table 250.102(C)(1). It is sized based on the largest ungrounded service-
entrance conductor(s). For paralleled conductors, sizing is based on the
equivalent total cross-sectional area.
22. How is the system bonding jumper sized?
Journeyman Electrician NEC 2026 Exam Prep — Bonding Jumpers & AC Systems | Page 3
, The SBJ is sized per NEC 250.102(C) using Table 250.102(C)(1), based on
the largest ungrounded supply conductor(s) of the SDS. For conductors
larger than 1100 kcmil copper or 1750 kcmil aluminum, the SBJ must be not
less than 12.5% of the area of the largest ungrounded conductor.
23. What is NEC Table 250.102(C)(1) used for?
NEC Table 250.102(C)(1) is used to size grounded conductors, main
bonding jumpers, system bonding jumpers, and supply-side bonding
jumpers. The table lists conductor sizes based on the size of the largest
ungrounded service or feeder conductor.
24. If service entrance conductors are 3/0 AWG copper, what is the
minimum MBJ size?
Per NEC Table 250.102(C)(1), with 3/0 AWG copper ungrounded
conductors, the minimum MBJ size is 4 AWG copper or 2 AWG aluminum.
25. If the largest ungrounded conductor is 500 kcmil copper, what is the
minimum SBJ size?
Per NEC Table 250.102(C)(1), with 500 kcmil copper conductors, the
minimum SBJ is 1/0 AWG copper or 3/0 AWG aluminum.
26. When does the 12.5% rule apply for bonding jumper sizing?
The 12.5% rule applies when the service or SDS supply conductors exceed
1100 kcmil copper or 1750 kcmil aluminum. In this case, the bonding jumper
must be at least 12.5% of the circular mil area of the largest ungrounded
conductor per NEC 250.102(C)(1).
27. How is the bonding jumper sized for paralleled service conductors?
Per NEC 250.102(C)(2), for paralleled service conductors, the total cross-
sectional area of all conductors per phase is calculated, and the bonding
jumper is sized based on that equivalent area using Table 250.102(C)(1).
28. What is the minimum size for an equipment bonding jumper on the
load side?
Load-side EBJs are sized per NEC 250.102(D) using Table 250.122, based
on the rating of the overcurrent device protecting the circuit. However, they
need not be larger than the circuit conductors.
29. Can a bonding jumper be installed in parallel?
Supply-side bonding jumpers may be installed in parallel when the
ungrounded conductors are paralleled in two or more raceways. The total
area must meet Table 250.102(C)(1) requirements per NEC 250.102(C)(2).
30. What is the minimum EBJ size for a circuit protected by a 100A
OCPD?
Journeyman Electrician NEC 2026 Exam Prep — Bonding Jumpers & AC Systems | Page 4
AC SYSTEMS | COMPREHENSIVE QUESTIONS AND VERIFIED ANSWERS | 100%
SUCCESS GUARANTEED
1. What is the primary purpose of bonding in an electrical system?
Bonding establishes a low-impedance path to facilitate the operation of
overcurrent protective devices (OCPDs) and reduce voltage differences
between conductive parts. Per NEC Article 250, bonding ensures electrical
continuity and capacity to safely conduct fault current.
2. What is the difference between bonding and grounding?
Grounding connects the electrical system to the earth (ground electrode),
while bonding connects metallic parts together and to the grounded
conductor. Bonding primarily protects people by limiting voltage differences;
grounding dissipates static charge and lightning energy.
3. Define 'bonding jumper' per NEC 2026 Article 100.
A bonding jumper is a reliable conductor that ensures the required electrical
conductivity between metal parts required to be electrically connected.
4. What is a Main Bonding Jumper (MBJ)?
The main bonding jumper (MBJ) is the connection between the grounded
circuit conductor (neutral) and the equipment grounding conductor (EGC) or
enclosure at the service. It is installed at the service entrance.
5. What is a System Bonding Jumper (SBJ)?
A system bonding jumper connects the grounded conductor to the supply-
side bonding jumper or the equipment grounding conductor, or both, at a
separately derived system (SDS). It performs the same function as the MBJ
but at an SDS.
6. Where is the main bonding jumper installed?
The MBJ is installed at the service disconnect enclosure, connecting the
neutral bus to the equipment grounding conductor or the enclosure itself. Per
NEC 250.24(B), it must be at each service disconnecting means.
7. What is a Supply-Side Bonding Jumper (SSBJ)?
A supply-side bonding jumper is a conductor installed on the supply side of a
service or separately derived system (SDS) to ensure the required electrical
Journeyman Electrician NEC 2026 Exam Prep — Bonding Jumpers & AC Systems | Page 1
, conductivity between metal parts required to be electrically connected.
Covered in NEC 250.102.
8. What is an Equipment Bonding Jumper (EBJ)?
An equipment bonding jumper is the connection between two or more
portions of the equipment grounding conductor. It ensures continuity of the
EGC path around intervening raceways, boxes, or enclosures.
9. How does NEC 2026 define a 'bonding conductor or jumper'?
NEC 2026 Article 100 defines it as a reliable conductor that ensures required
electrical conductivity between metal parts required to be electrically
connected. This includes both conductors and other conductive means (e.g.,
metal raceways used as EGCs).
10. What NEC article primarily covers grounding and bonding?
NEC Article 250 covers grounding and bonding. It includes requirements for
system grounding, equipment grounding, bonding conductors, and
grounding electrode systems.
11. What is the difference between a bonding jumper and a grounding
electrode conductor?
A bonding jumper connects metallic parts together for equipotential
purposes. A grounding electrode conductor (GEC) connects the electrical
system to the grounding electrode system (earth connection). They serve
different but complementary purposes.
12. What does NEC 250.4(A)(1) require regarding grounded systems?
NEC 250.4(A)(1) requires that electrical systems be grounded where they
can be grounded so that the maximum voltage to ground from ungrounded
conductors does not exceed 150 volts (for certain system voltages), to limit
voltage imposed by lightning or line surges.
13. What is 'effective ground-fault current path'?
An electrically conductive path from the point of a ground fault on a wiring
system through normally non-current-carrying conductors, equipment, and
the earth, if applicable, to the electrical supply source. Per NEC 250.4(A)(5),
it must be permanent, electrically continuous, with sufficient capacity to
conduct safely any fault current likely to be imposed on it.
14. What are the two types of bonding jumpers covered in NEC 250.102?
NEC 250.102 covers (1) Supply-side bonding jumpers (at the supply side of
service equipment or SDS), and (2) Equipment bonding jumpers (on the load
side connecting EGC paths).
Journeyman Electrician NEC 2026 Exam Prep — Bonding Jumpers & AC Systems | Page 2
,15. Can the neutral conductor serve as the EGC in a multi-wire branch
circuit?
No. The neutral (grounded) conductor can only serve as the EGC on the
supply side of the service point or SDS. On the load side of service
equipment, the neutral and EGC must be separate per NEC 250.142.
16. What is the function of bonding at a service?
Bonding at the service connects the grounded conductor (neutral), EGC, and
all non-current-carrying metal parts together and to the grounding electrode
system, ensuring a low-impedance fault-current path that allows OCPDs to
operate properly.
17. What is 'equipotential bonding'?
Equipotential bonding connects all conductive parts that may differ in
potential, ensuring they are at the same voltage. This reduces the risk of
electric shock from voltage differences. Common applications include
swimming pools and agricultural facilities.
18. Can a bonding jumper be a bare conductor?
Yes. Bonding jumpers may be bare, covered, or insulated conductors. NEC
250.119 requires EGCs to be identified by green or green with yellow stripe
coloring, or bare, when insulated.
19. What is the maximum length allowed for the main bonding jumper?
NEC does not impose a maximum length restriction on the MBJ, but it must
be installed within the service disconnect enclosure or between the service
disconnect and the grounded conductor connection. Practically, it should be
as short as possible.
20. What happens if the MBJ is omitted or improperly installed?
Without the MBJ, the neutral is not bonded to the EGC at the service, which
means the neutral will be floating relative to the equipment enclosure. This
can result in dangerous voltage on metal enclosures and OCPDs may fail to
operate during a fault.
SECTION 2: SIZING BONDING JUMPERS
21. How is the main bonding jumper sized?
Per NEC 250.28(D), the MBJ must not be smaller than specified in NEC
Table 250.102(C)(1). It is sized based on the largest ungrounded service-
entrance conductor(s). For paralleled conductors, sizing is based on the
equivalent total cross-sectional area.
22. How is the system bonding jumper sized?
Journeyman Electrician NEC 2026 Exam Prep — Bonding Jumpers & AC Systems | Page 3
, The SBJ is sized per NEC 250.102(C) using Table 250.102(C)(1), based on
the largest ungrounded supply conductor(s) of the SDS. For conductors
larger than 1100 kcmil copper or 1750 kcmil aluminum, the SBJ must be not
less than 12.5% of the area of the largest ungrounded conductor.
23. What is NEC Table 250.102(C)(1) used for?
NEC Table 250.102(C)(1) is used to size grounded conductors, main
bonding jumpers, system bonding jumpers, and supply-side bonding
jumpers. The table lists conductor sizes based on the size of the largest
ungrounded service or feeder conductor.
24. If service entrance conductors are 3/0 AWG copper, what is the
minimum MBJ size?
Per NEC Table 250.102(C)(1), with 3/0 AWG copper ungrounded
conductors, the minimum MBJ size is 4 AWG copper or 2 AWG aluminum.
25. If the largest ungrounded conductor is 500 kcmil copper, what is the
minimum SBJ size?
Per NEC Table 250.102(C)(1), with 500 kcmil copper conductors, the
minimum SBJ is 1/0 AWG copper or 3/0 AWG aluminum.
26. When does the 12.5% rule apply for bonding jumper sizing?
The 12.5% rule applies when the service or SDS supply conductors exceed
1100 kcmil copper or 1750 kcmil aluminum. In this case, the bonding jumper
must be at least 12.5% of the circular mil area of the largest ungrounded
conductor per NEC 250.102(C)(1).
27. How is the bonding jumper sized for paralleled service conductors?
Per NEC 250.102(C)(2), for paralleled service conductors, the total cross-
sectional area of all conductors per phase is calculated, and the bonding
jumper is sized based on that equivalent area using Table 250.102(C)(1).
28. What is the minimum size for an equipment bonding jumper on the
load side?
Load-side EBJs are sized per NEC 250.102(D) using Table 250.122, based
on the rating of the overcurrent device protecting the circuit. However, they
need not be larger than the circuit conductors.
29. Can a bonding jumper be installed in parallel?
Supply-side bonding jumpers may be installed in parallel when the
ungrounded conductors are paralleled in two or more raceways. The total
area must meet Table 250.102(C)(1) requirements per NEC 250.102(C)(2).
30. What is the minimum EBJ size for a circuit protected by a 100A
OCPD?
Journeyman Electrician NEC 2026 Exam Prep — Bonding Jumpers & AC Systems | Page 4
