125 volt

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kimrichi

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What does it mean when we say recepticle with 125 volt rating and when
Current goes up when we reduce voltage. Or visa versa although that contradicts with Oams law
 

infinity

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The relationship between current and voltge is dependent on the type of load. So your example may not defy Ohm's law.
 

hbiss

EC, Westchester, New York NEC: 2014
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I don't know what you are asking. A 125 volt receptacle is rated that way mainly because of it's configuration but also it's insulation is designed for 125 volt use. Nothing to do with Ohm's law.

As far as your second question (I think) about the relationship between voltage, current and Ohm's law. For a given resistance, increasing the voltage across it will result in a corresponding increase in current through it. However, if you keep the voltage constant and increase the resistance the current will decrease. Is that what you are thinking?

-Hal
 

Rick Christopherson

Senior Member
The relationship between current and voltge is dependent on the type of load. So your example may not defy Ohm's law.
I don't know if it is what you are referring to, but in another thread earlier today someone made the comment about current going up when voltage goes down (as per motors). This is a common misunderstanding with many people because they see current rise with undervoltage conditions on motors. However, the current increases because the motor is slowing, and its impedance is dropping. The rise in current is not because the voltage went down, per se.

Ohm's Law still applies, and current and voltage will follow each other. It's the R (or Z) that is also changing in this case that gets overlooked.
 

kimrichi

Member
I don't know what you are asking. A 125 volt receptacle is rated that way mainly because of it's configuration but also it's insulation is designed for 125 volt use. Nothing to do with Ohm's law.

As far as your second question (I think) about the relationship between voltage, current and Ohm's law. For a given resistance, increasing the voltage across it will result in a corresponding increase in current through it. However, if you keep the voltage constant and increase the resistance the current will decrease. Is that what you are thinking?

-Hal
i dont know what insulation you mean for a receptacle besides when i have 120 circuit why receptacle is 125 volts and not 120
for the other part mike holt stated in one of his experments cut the feeder neutral and the flourescent bulbs burned he said because undervoltage current went high and caused the burned bulbs
 

mivey

Senior Member
i dont know what insulation you mean for a receptacle besides when i have 120 circuit why receptacle is 125 volts and not 120
120 volts is the "nominal" rating. We routinely see voltages above 120 and 125 is more the norm. We are usually starting at about a 126 volt reference level at the substation (5% above 120 volts).

for the other part mike holt stated in one of his experments cut the feeder neutral and the flourescent bulbs burned he said because undervoltage current went high and caused the burned bulbs
Where is that? Need more context.
 

kimrichi

Member
120 volts is the "nominal" rating. We routinely see voltages above 120 and 125 is more the norm. We are usually starting at about a 126 volt reference level at the substation (5% above 120 volts).

Where is that? Need more context.

In a dvd about commercial calcualation
 

Little Bill

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i dont know what insulation you mean for a receptacle besides when i have 120 circuit why receptacle is 125 volts and not 120
for the other part mike holt stated in one of his experments cut the feeder neutral and the flourescent bulbs burned he said because undervoltage current went high and caused the burned bulbs

120 volts is the "nominal" rating. We routinely see voltages above 120 and 125 is more the norm. We are usually starting at about a 126 volt reference level at the substation (5% above 120 volts).

Where is that? Need more context.

Sorry. Don't have it. Not quite sure of the details of what Mike was saying so I can't be of much help.

Sounds like he (MH) was describing what could happen if the neutral was broken on a MWBC. You could get under voltage on one leg and over voltage on the other, causing whatever was on the leg with the high voltage to be damaged.
 
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