Need help on 6.2 and 6.3. 6.1. A circuit breaker-GFCI combination was in- contac

Question

Need help on 6.2 and 6.3.

6.1. A circuit breaker-GFCI combination was in- contacts the energized terminal of the plug be- fore its contact with the receptacle is broken. stalled in a residence service panel. (This is an actual case that happened in Ames.) The GFCI was installed to protect an outdoor re- ceptacle and a bathroom receptacle. When loads were plugged into the bath receptacle only, they operated normally. When any load was plugged into the outdoor receptacle, the GFCI tripped and power to bath and outdoor receptacles was shut off even though no ground fault existed. Draw the circuit as in- correctly wired. (a) Scenario I: The receptacle is not GFCI protected and the person is standing on a wet concrete floor. Explain what is likely to hap- pen, and why. (b) Scenario II: The receptacle is GFCI- protected and the person is standing on a wet concrete floor. Explain what is likely to hap- pen, and why. 6.2. As a person removes a 120-V plug from a wall receptacle, the person's right thumb and index finger simultaneously contact the neu- tral and energized terminals of the piug befcae their contact with the receptacle is (c) Scenario III: The receptacle is not GFCI- protected and the person is standing on a dry rubber mat. Explain what is likely to happen, (a) Scenario I: The receptaclei protected and the person is standing on a wet concrete floor. Explain what is likely to hap- pen, and why. (d) Scenario IV: The receptacle is GFCI- protected and the person is standing on a dry rubber mat. Explain what is likely to happen, and why An adult person is drawing a 200-mA hand- to-hand ground fault shock on a 15-A branch circuit having no other load. 6.4. (b) Scenario II: The receptacle is GFCI- protected and the person is standing on a wet concrete floor. Explain what is likely to hap- pen, and why (a) How long can the person endure this shock before fibrillation is likely? (c) Scenario III: The receptacle is not GFCI- ected and the person is standing on a dry rubber mat. Explain what is likely to happen, (b) What is the maximum trip time allowed if the GFCI is to meet the UL standard for Class A GFCIs? (d) Scenario IV: The receptacle is GFCI (c) What is the typical trip time for a GFCI under this condition? protected and the person is standing on a dry rubber mat. Explain what is likely to happen, and why 6.5. The branch circuit overcurrent device on a person removes a 120-V plug from a all receptacle, the person's right index finger motor circuit is a standard circuit breaker rated at 10A

Explanation / Answer

Answer:-6.2)a) The person will get electric shok, since current flows from hot(energized line) to ground through body and to neutral through thumb.

b) Since GFCI protected and some current flows to ground from hot through body of person, hence power of circuit breaks and person is safe. Note GFCI breaks circuit in 1/30 th of second.

c) Though person is standing on dry rubber mat still person will get shok since thumb is in contact with neutral and hence there is a path of currnet flow from hot to neutral.

d) since in this case total current comming out from hot is equal to total current going out to neutral hence GFCI doesn't breaks the circuit and person gets electric shok.

Answer:-6.3)a) So here a part of current flows from hot to ground, hence person gets electric shok.

b) Since GFCI protected, the power to circuit breaks since hot output current is not equal to neutral input current since some current goes to ground throgh person's body. So person is safe here. Note GFCI breaks circuit in 1/30 th of second.

c) No contact with ground due to rubber mat hence no current flows through person's body. The person is safe.

d) Again no current flows through person's body and there is no difference in hot output current and neutral input current so GFCI doesn't breaks the circuit. The person is safe.

NOTE:- Touching any one wire at a time is safe if we are not in contact with ground.

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