Grounding and bonding theory Quiz -1
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Free online test on Grounding and bonding ( National Electrical Code – 250)
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Question 1 of 10
1. Question1 points
Grounding in electrical system limit the high current and thus reduces the damage.Correct
Refer : NEC 250.2 A
Grounding limits the high voltage in electrical system.
Question 2 of 10
2. Question1 points
The secondary systems of lighting circuits shall not be grounded.Correct
Refer : NEC 411.5
Question 3 of 10
3. Question1 points
An additional grounding connection shall me made to the transformer supplying the feeder service in the building.Correct
Refer : NEC 250.24 (2)
Addiotnal grounding shall be provided if the service is located outside the building.
Question 4 of 10
4. Question1 points
The grounded conductor ampacity of a delta connected 3-phase 3-wire system must be less the rating of …………………………….Correct
Refer : NEC 250.24 (c)(3)
Question 5 of 10
5. Question1 points
In a single raceway the size of the grounded conductor shall not be larger than the ungrounded conductor in the raceway.Correct
Refer : NEC 250.24 (c)(1)
Shall not be larger than the largest ungrounded conductor in a raceway
Question 6 of 10
6. Question1 points
In a single phase three wire electrical system, the middle conductor of a 3-wire should be which of the following?Correct
Refer : NEC 250.26
Single phase 3-wire – Middle conductor(neutral conductor) shall be grounded.
Question 7 of 10
7. Question1 points
Mostly grounding wires are identified which of the following color?Correct
Question 8 of 10
8. Question1 points
The grounded wire shall never be interrupted by a circuit breaker or a fuse.Correct
The grounded wire can be interrupted by any device (circuit breaker or fuse) when it is simultaneously opens all the ungrounded conductors of the electrical system
Question 9 of 10
9. Question1 points
In a single phase electrical system the size of the largest ungrounded service entrance aluminum conductor is 1/0 AWG, which of the following is the size of the grounding conductor?Correct
Refer : NEC Table 250.66
Question 10 of 10
10. Question1 points
The lighting system protection ground terminals shall be bonded to which of the following grounding electrode system?Correct
Refer : NEC 250.106
Grounding and Bonding :
Grounding of an electrical system should be done to limit high voltage causes by lighting strikes or any miss-contact of low voltage wires with high voltage wires. This is categorized into two categories:
System Grounding :
This refers grounding non current carrying parts of the electrical installation such as service equipment cabinet, the frames of an electric motor.
Important Notes :
- The grounded wire is never interrupted by a circuit breaker, fuse or any other device unless the device used is so designated that in opening the grounding conductor opens all other ungrounded conductors at the same time.
- As per the Code the grounded wire to be identified by a white or natural grey finish through out its length.
- As per code all receptacles 15 and 20 amp circuits, at 120 volts should be of grounding type.
- The voltage to ground is the maximum voltage that exists between ground wire and any hot wire in the circuit.
GFCI (Ground Fault Circuit Interceptor):
GFCI will be used to sense the difference between two wires, and if the fault current increases the trip level of GFCI, it will opens the circuit with in no time.
1) In dwelling units on all 15 and 20 amp outdoor receptacles on all bathroom and garage receptacles should be fitted with GFCI protection.
2) GFCI protection should be provided in construction site 15 and 20 amp receptacles which are not part of the permanent wiring of the building or structure.