Written against the 2026 NEC and checked section by section, September 2026
Grounding vs Bonding Practice Questions
Grounding heads for the earth and bonding heads back to the source, and Article 250 keeps the two jobs apart even where the field uses one word for both. These 25 items work the performance requirements at 250.4, the Article 100 definitions the exam builds distractors from, the objectionable current rules at 250.6, and the sorting question that decides whether a conductor sizes from 250.66 or from 250.122.
Pick an answer and the explanation opens with the section it comes from. These are original questions written for this site, not questions from the exam. Have your own code book open: the Texas exam is open book, and looking the section up is the skill being tested.
Read the grounding vs bonding study page first if the topic is new to you.
1. The performance requirements say what a connection to earth accomplishes on a grounded system. What is that job?
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A. Limiting the voltage imposed by lightning, line surges and unintentional contact with higher voltage lines, and holding the voltage to earth stable in normal operation
The earth connection is a voltage job, not a current job. Everything in that subdivision is about limiting or stabilizing voltage, and nothing in it mentions opening a device. The option about clearing a fault belongs to the bonded metal path, which is a separate subdivision entirely.
NEC 2026 250.4(A)
2. Article 100 defines the word ground in two words. What are they?
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B. The earth
Ground is defined as the earth and nothing else. That two word definition is what keeps grounded and bonded from meaning the same thing, since grounded means connected to ground or to a body that extends that connection. An option naming a conductor is naming hardware, not the definition.
NEC 2026 Article 100
3. Two metal enclosures are joined so that they are electrically continuous with each other. Neither has any connection to earth. Under the Article 100 definitions, what has been done?
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C. They have been bonded, since bonding is a connection made to establish electrical continuity and conductivity
The bonding definition says nothing about the earth. It asks only for continuity and conductivity between conductive parts, which is exactly what the described connection produces. Grounding needs a connection to ground or to something that extends that connection, and no such connection exists here.
NEC 2026 Article 100
4. Article 100 describes an equipment bonding jumper as a component of what?
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D. The effective ground-fault current path, connecting two or more portions of the equipment grounding conductor
The definition puts this jumper squarely on the fault path side and says what it joins, which is portions of the equipment grounding conductor. The electrode answer describes the grounding electrode bonding jumper, a different defined term that sizes from a different table.
NEC 2026 Article 100
5. What separates a main bonding jumper from a system bonding jumper?
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B. Where it is installed, the main one at the service equipment and the system one at a separately derived system
Both definitions describe the same connection between the grounded circuit conductor and the fault path, and the location is the only thing that changes. The material rules run together for the two, so an answer that assigns a wire to one and a screw to the other is inventing a distinction.
NEC 2026 Article 100, 250.28
6. Supply conductors run to a service in a single raceway. Which table sizes the supply-side bonding jumper?
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C. Table 250.102(C)(1)
A supply-side bonding jumper is sized on the service conductor it runs with, and that is the table the subsection points at. Table 250.122 is keyed to an overcurrent device rating, which is a load side idea, and there is no device between the utility and the service disconnect to key it to.
NEC 2026 250.102(C)(1), Table 250.102(C)(1)
7. A jumper connects one driven rod to a second driven rod. Which rule sizes it?
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D. 250.66, because the conductor is on the grounding electrode side
That section sizes the grounding electrode conductor and the bonding jumpers used to connect electrodes, which is what this jumper is. Sorting on the word bonding sends candidates to the fault path tables and produces a number that is not among the options. Ask which way the conductor is headed rather than what it is called.
NEC 2026 250.66, Article 100
8. A service raceway lands in an oversized knockout at the service enclosure. What does the bonding rule for services require?
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A. A bonding jumper around the impaired connection
The service bonding subsection names reducing washers and oversized, concentric or eccentric knockouts as impaired connections and calls for a jumper around them. Standard locknuts and bushings may be installed to make the mechanical connection, but the section does not accept them as the bonding means by themselves.
NEC 2026 250.92
9. A feeder on a 480Y/277 volt system runs in metal raceway. What extra requirement reaches the continuity of that raceway?
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C. Continuity is ensured by the service bonding methods, with the one method the section excludes left out
This is the over 250 volts to ground rule, and 277 volts to ground clears that threshold. It pulls the service bonding methods onto ordinary raceways that contain something other than service conductors, and it drops one of those methods on the way. The voltage in the stem is the whole trigger.
NEC 2026 250.97, 250.92
10. The performance requirements are written twice, once for grounded systems and once for ungrounded ones. On an ungrounded system, what does the code ask of the metal that encloses conductors?
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D. That it be connected to earth in a way that limits the voltage put on it by lightning or by contact with a higher voltage line
The two sets of performance requirements run in nearly the same wording, and the ungrounded set still asks for the enclosing metal to reach earth and to be bonded back to the supply. What an ungrounded system leaves out is the connection of a circuit conductor to earth, not the connection of the equipment. Read which one the item is about before you answer.
NEC 2026 250.4(B)
Ten down. If you want these timed and scored by content area, the practice exam runs thirty questions free, and the full bank of 178 plus the calculation ladder is $79 once.
11. A raceway runs through a Class I, Division 2 location on a 208Y/120 volt system. What decides whether the special bonding methods apply?
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A. Nothing about the system voltage, because those methods apply regardless of voltage
Everywhere else in the book, supplemental bonding turns on voltage or on what is in the raceway. In a classified location the requirement opens by saying the voltage does not matter, and it holds whether or not a wire type equipment grounding conductor is pulled. That is the exception candidates walk past because they just learned the general rule.
NEC 2026 250.100, 500.30
12. An isolated equipment grounding conductor is run to electronic equipment to keep noise off it. What does that do to the requirement for an effective ground-fault current path?
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B. Nothing, since the isolated conductor is in addition to that path rather than a substitute for it
The isolated grounding subsection permits the arrangement and then carries a note saying the isolated conductor does not relieve the requirement for an effective ground-fault current path. Read that as two conductors doing two jobs. The metal path still has to be there and still has to be capable of carrying fault current.
NEC 2026 250.96
13. Objectionable current is found flowing on building metal. One permitted alteration is to discontinue grounding or bonding connections. What limit does the section put on that?
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D. One or more of those connections may be discontinued, but not all of them
The alteration reads one or more but not all, and the last three words are the whole item. Four alterations are offered and every one of them assumes the required fault path survives the fix. Stripping the last connection would take away the path the rest of the article exists to build.
NEC 2026 250.6
14. Which of these currents is specifically not classified as objectionable current?
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A. Current flowing during a ground fault
The section says currents from abnormal conditions such as ground faults, and currents produced by the grounding and bonding connections the code requires, are not the objectionable current it is aimed at. Fault current is the current the system was built to carry. The other three are neutral current on a path that was never meant to carry it.
NEC 2026 250.6
15. A hum in an audio rack stops when the equipment grounding conductor is lifted. What does the objectionable current section say about that?
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B. It does not permit electronic equipment to be operated on a circuit with no equipment grounding conductor
A subsection is written specifically to close this door, and it says the permitted alterations are not a license to run electronic gear without the equipment grounding conductor the article requires. Electromagnetic interference and data errors are named as something other than the objectionable current the section is about.
NEC 2026 250.6
16. Which method is not permitted for connecting grounding and bonding equipment?
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C. A connection device that depends only on solder
The permitted list runs to eight entries and covers pressure connectors, terminal bars, welding, screws that catch two threads and connections that are part of a listed assembly. A separate short subsection rules out anything that relies on solder alone, because solder softens at the temperatures a fault produces.
NEC 2026 250.8
17. A painted enclosure is going to be bonded. What does the code require at the contact surfaces?
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A. The coating is removed from threads and contact surfaces, or a fitting designed to make removal unnecessary is used
Paint, lacquer and enamel are named as nonconductive coatings and the section wants them gone from the surfaces that carry the connection. The alternative it offers is hardware built to cut through, which is why paint-piercing washers and locknuts exist. Upsizing a jumper does nothing about a joint that is insulated.
NEC 2026 250.12
18. The general bonding section names two things a bond has to accomplish. What are they?
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C. Electrical continuity, and the capacity to carry safely any fault current likely to be imposed
Continuity alone is not the test. A joint can be continuous enough for a meter and still fail under the current a fault puts through it, so the section asks for carrying capacity in the same sentence. The 25 ohm figure belongs to a rod electrode rule and has nothing to do with bonding.
NEC 2026 250.90
19. Which of these is permitted to serve as a bonding jumper?
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B. A nonflexible metal raceway with its fittings
The material subsection lists a wire, a bus, a screw, a nonflexible metal raceway and its fittings, or a similar suitable conductor, in copper, aluminum, copper-clad aluminum or another corrosion-resistant material. Bare aluminum in concrete is ruled out by the installation rules for that metal, and the piping option confuses something that gets bonded with something that does the bonding.
NEC 2026 250.102
20. A bonding jumper is installed on the outside of a raceway rather than inside it. What length limit applies?
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D. 6 feet, and it is routed with the raceway
Inside a raceway the jumper follows the identification and box rules. Outside it, the code caps the length and asks that the jumper follow the raceway rather than take a shortcut, because a long jumper on its own path adds impedance to the fault loop. An exception opens that up at outdoor pole locations and for bonding electrodes.
NEC 2026 250.102
21. Service conductors are 1/0 AWG copper in a single raceway. What is the minimum size copper supply-side bonding jumper from the table?
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C. 6 AWG
The row that covers 1 AWG and 1/0 AWG copper gives 6 AWG copper. The 8 AWG answer is the row above it, which stops at 2 AWG copper, and it is the one you land on by reading up a line under time pressure. Check that the material column you are reading matches the material in the stem.
NEC 2026 Table 250.102(C)(1)
22. One common continuous equipment bonding jumper joins two metal raceways on the load side of a 100 ampere overcurrent device. What size copper conductor does the code call for?
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A. 8 AWG
A single jumper is permitted to serve two or more raceways, and it is sized on the largest overcurrent device supplying circuits in them. The 100 ampere row of the equipment grounding conductor table gives 8 AWG copper. Nothing about the number of raceways changes the size, which is what makes the permission useful.
NEC 2026 250.102(D), Table 250.122
23. A service uses 2/0 AWG copper ungrounded conductors. What size copper grounding electrode conductor does the table call for?
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D. 4 AWG
The row covering 2/0 and 3/0 copper gives 4 AWG copper. Two ceilings sit outside the table and catch people who never read past it, since a conductor running only to a rod, pipe or plate electrode stops at 6 AWG copper and one running only to a concrete encased electrode stops at 4 AWG copper.
NEC 2026 Table 250.66, 250.66
24. Which of these is not listed in the scope of Article 250?
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B. The ampacity of the ungrounded circuit conductors
The scope runs to six items and every one of them is about grounding and bonding, including which systems are required, permitted or not permitted to be grounded and which circuit conductor is the grounded one. Ampacity is Article 310 work. Scope items appear on the exam because they let a writer test whether you know which article to open.
NEC 2026 250.1
25. Two conductors on one job are both called bonding jumpers. One ties a metal water piping system to the service enclosure, and one ties two sections of metal raceway together on a 200 ampere feeder. Which rules size them?
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A. The piping jumper from Table 250.102(C)(1) and the raceway jumper from 250.122
The piping bonding rule points at the service conductor table and adds a ceiling of 3/0 copper. The raceway jumper is an equipment bonding jumper on the load side of an overcurrent device, so it sizes on the device rating instead. Same two words in both names, two different tables, decided by which side of the service the conductor sits on.
NEC 2026 250.104, Table 250.102(C)(1), 250.102(D), 250.122
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