Test Lamps

[erickench]

Look at this question and the answer as given by the answer key.

A panelboard has four bus-bars and a nameplate with the information 3-phase, 4-wire A.C. 208/120V. If a lamp test set is to be used to determine which of the bus-bars is the neutral, you should for safety reasons, use

A. one 120-volt lamp
B. two 120-volt lamp
C. one 120-volt, 300-watt lamp
D. two 120-volt lamps connected in series

The answer as given by the answer key is 'D' two 120-volt lamps connected in series. I assume that this so because you may have to test across two phases at 208 volts and a single 120 volt lamp would not be able withstand that.

 

[K8MHZ]

Look at this question and the answer as given by the answer key.

A panelboard has four bus-bars and a nameplate with the information 3-phase, 4-wire A.C. 208/120V. If a lamp test set is to be used to determine which of the bus-bars is the neutral, you should for safety reasons, use

A. one 120-volt lamp
B. two 120-volt lamp
C. one 120-volt, 300-watt lamp
D. two 120-volt lamps connected in series

The answer as given by the answer key is 'D' two 120-volt lamps connected in series. I assume that this so because you may have to test across two phases at 208 volts and a single 120 volt lamp would not be able withstand that.

Who writes this stuff????

Show me a test lamp set where two lamps are connected in series.

I'll bet there is no CAT rating, and no UL listing as such a set would likely be home brew.

Why not just grab a CAT rated meter and check the proper way?

 

[hurk27]

This is an old test question that has been around for quit some time, I can remember getting it on several older test I took in the past. and D is the correct answer.

you should always test for voltage with test equipment rated for the highest available voltage you might encounter, in this case the 208 between phases.

When I started out back in "74" using lamps was a very common test method, and for some test still is, one of the best circuit testers there is, is a lamp on the end of an extension cord, plugged in to the receptacle that lost power, while you go around and wiggle other receptacles, or for shorts, by putting a lamp in between the faulted circuit and its breaker, again on the end of an extension cord, so when you find the fault and open it, you know it.

Where are you getting these questions?

 

[hurk27]

Who writes this stuff????

Show me a test lamp set where two lamps are connected in series.

I'll bet there is no CAT rating, and no UL listing as such a set would likely be home brew.

Why not just grab a CAT rated meter and check the proper way?

Do you know what simple thing cause
the coming out with cat ratings?

The 10 amp banana plug hole on most VOM and DVM meters, it was a shunt bar to the NEG/common plug, and many meters didn't even have a fuse in-line with it, accidentally put your red lead in that hole and try to test for voltage on a 480 volt system and you got one burnt electrician.

 

[muskrat]

This is an old test question that has been around for quit some time, I can remember getting it on several older test I took in the past. and D is the correct answer.

you should always test for voltage with test equipment rated for the highest available voltage you might encounter, in this case the 208 between phases.

When I started out back in "74" using lamps was a very common test method, and for some test still is, one of the best circuit testers there is, is a lamp on the end of an extension cord, plugged in to the receptacle that lost power, while you go around and wiggle other receptacles, or for shorts, by putting a lamp in between the faulted circuit and its breaker, again on the end of an extension cord, so when you find the fault and open it, you know it.

Where are you getting these questions?

Remember the old "main-range-and -four" 60 amp service w/ screw in fuses?
Learned to use a light bulb in the fuse holder when there's a direct short. Bulb stays lit till the short is cleared. (showing my age)

 

[erickench]

Where are you getting these questions?

I'm taking a civil service test for a job. This question came from a recently purchased passbook that prepares you for the test.