If E over I R = Ohms law then. What happens to the amperage when the voltage is lowered.?

Question

I have worked with many electricians and electrical contractors over my 24 years in the electrical field and have asked this question on the job many times and I was surprised that no one got it right except one, and he is an electronics engineer.

Answer 1

Volts down, amperage goes with it. Ohms law explains that.

Answer 2

Voltage and amperage are inversely proportional in a constant resistance. The lower the voltage the higher the amperage and therefore the higher the heat.

Answer 3

E = voltage, I = Current, R = Resistance

=> now Ohm's law in its common form is V = I*R

if Voltage is lowered, so is the "Amperage" or current. Only difference is that IF the Resistance R stays constant then the current I is lowered by a constant magnitude of R.

Example:

Initially,
V = 5 [V]
I = 5 [mA]
R = 1000 [Ohms] => (CONSTANT RESISTANCE)

but let's say, we lower the voltage to 2[V], so, the current will go down by a magnitude of 1000 and the current will equal 2[mA].

2[V] = 2[mA] * 1000[Ohms]
2[V] = 2[V]

Answer 4

If Voltage is lowered and resistance remains the same then current will necessarily decrease.

If we have 10 volts across a 1 ohm resistor, we have a current of 10 amperes. If we reduce the current to 5 amperes, the voltage equals 5 volts.

Then again, I'm an engineer.

Answer 5

Actually Ohm's law is E = IR, not over. Putting E (voltage) over the I (amperage) and R (resistance) symbols is an easy way to remember all the different forms of Ohm's law. All you have to do is place your finger over the variable you want to solve for, and the equation is spelled out for you.


Anyway, on to your question:
If voltage is lowered, and the resistance remains the same, then the current gets smaller.
The equation you are looking for is:
I = E/R

Answer 6

E = I x R
I = E ÷ R

As the voltage goes down, so does the current.

The exception to this is motor load. Induction motors are a constant power device. As the voltage goes down, the current goes up.


Electric utilities will lower the distribution system voltage to lower the overall load. This is done to maintain system stability during periods when demand is nearing supply. Typical voltage reductions are 2½% at the substation bus. Under extreme conditions it may be lowered a total of 5%. These "low voltage" conditions are what is commonly referred to as a "brown out".

While utilities serve a mix of inductive and resistive load, the overall effect of lowering the voltage is reduced consumption.

Answer 7

V= I*R
100 = I * 100 ohms 50 = I *100 ohms
1 amp = I 50/ 100 = I
500 mA = I

The current is also lowered. Notice that I kept the resistance the same.

Answer 8

It goes down of course. Look at that equation. If has the voltage on the left and the amperage on the right. If one goes down the other must also.

Answer 9

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V=IR, R=V/I, I=V/R Watts=current x voltage

Answer 10

E Over I R