Ohm's Law

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Not that I know of......I was always taught that voltage goes up, current down.

Now I would believe that some freaky engineer type from MIT could do it!:grin:
 
in a resistive circuit (aka linear), as the voltage increases so does the current (V=IR) graph it, get yourself a power supply and a resistor, you will see.

In an inductive circuit the inductor tends to do what you described.

this is circuit theory for linear ckts, RC ckts, RLC ckts - pick up a book on basic ckt theory and it will explain much better than I ever could.
 
I got someone on this today. He said that voltage and current cannot increase simutaneously and I said not neccessarily. I showed them a very basic DC equation using Ohm's Law of I=E/R.

E R I
2v 5ohms = 0.4A
4v 5ohms = 0.8A
6v 5ohms = 1.2A

"Ohm's law cannot be applied to alternating-current circuits since it does not consider the reactance which is always present in such circuits. However, by a modification of Ohm's law which does take into consideration the effect of reactance, we obtain a general law which is applicable to AC circuits. Because the impedance, Z, represents the combined opposition of all the reactances and resistances, this general law for AC is:
I=E/Z." (TECHNOTE TIME)
 
memyselfandI said:
Can you increase voltage and current simultaneously?
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Thats exactly what happens in a DC circuit or an AC circuit with a resistive load. As stated ohms law rules Amps = Voltage/resistance. If the resistance is constant, the amps will increase with the voltage

barbeer said:
Not that I know of......I was always taught that voltage goes up, current down.
Now I would believe that some freaky engineer type from MIT could do it!:grin:
Click to expand...
I believe that idea comes from the electrical motor characteristics. The motor current tends to go up if the voltage decreases assuming the torque is constant.
 
Actually from a basic level, you can't "increase" current. By that I mean that current is a function of the load. A load PULLS current, you don't PUSH current into something.

However in the resistive circuit examples above, if the resistance stays the same, then increasing the voltage will cause the load to pull more current.
 
Jraef said:
Actually from a basic level, you can't "increase" current. By that I mean that current is a function of the load. A load PULLS current, you don't PUSH current into something.
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I'm not sure that is a good analogy at all. To me, it is more correct to say that voltage "pushes" current than to say that a load "pulls" current. The voltage is active, whereas a resistor is passive. I guess the whole thing is rather arbitrary though.
 
Now, I think the OP (memyselfandI) needs to further clarify his question.

I think he is referring to items such as a transformer. From the primary to the secondary, if we decrease voltage, then we have an increase in current capacity. If we increase the voltage using the transformer, we get a decrease in the current capacity.... you know, all based on the fact that the power in the secondary equals the power in the primary when considering a theoretically perfect xfmr.

So if that is the OPs question, then the answer is "no".... we cannot increase both the voltage and current at the same time in a xfmr or other type of "amplifying" device....

unless we add energy from an external source, for example, a generator. We can take a relatively small voltage and small current to excite the field, and by adding energy of rotation, we can create a higher voltage and a higher current together.

Same thing is true of an amplifier. To make a gain in both current and voltage would require input of some other energy. Of course, this is done routinely, but we are not getting something for nothing power-wise.

Was that the question?

Edit to add: Obviously, if we take the question at face value, everyone above who pointed out that with a fixed resistance or impedance, raising the voltage will raise the current.
 
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barbeer said:
Not that I know of......I was always taught that voltage goes up, current down.

Now I would believe that some freaky engineer type from MIT could do it!:grin:
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They taught you very wrong. Mr. Ohm said that the current in a circuit depends upon how much pressure is pushing against how much resistence.
 
bob said:
I'm not following you Jim.
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OOPS - you can't go back and edit out a mistake.
Ohms law says that voltage and current are directly proportional E=IR if the resistance is constant. However if the load is a constant power device P=IE, thus voltage and current are inversely related and R is not a constant.
 
jim dungar said:
OOPS - you can't go back and edit out a mistake.
Ohms law says that voltage and current are directly proportional E=IR if the resistance is constant. However if the load is a constant power device P=IE, thus voltage and current are inversely related and R is not a constant.
Click to expand...
Is P=IE part of Ohm's law or a modification for use on AC circuits?
 
memyselfandI said:
Is P=IE part of Ohm's law or a modification for use on AC circuits?
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P= IE applys to AC and DC circuits. However in AC circuits you must take into account the power factor.
 
jim dungar said:
Ohms law says that voltage and current are directly proportional E=IR if the resistance is constant. However if the load is a constant power device P=IE, thus voltage and current are inversely related and R is not a constant.
Click to expand...

I like Mr. Jim Dugar's posts best this time around.

Here’s a spin: The current goes up when the voltage is raised at a given frequency by changing the volts/hertz curve.

Can of worms? Resistance is futile!

PS – I was doing this VFD last night when a breaker interrupted us
 
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