Understanding Ohm's Law: E/E & U (Voltage) Explained

[Mohamad&Issa]

In ohm's law for a receiver or generator I couldn't understood the difference between e/E and U(voltage).
So please can anybody help me in this?

 

[gneill]

In ohm's law for a receiver or generator I couldn't understood the difference between e/E and U(voltage).
So please can anybody help me in this?

Hi M&I. The use of e, E, V, U, etc., to represent potential difference is a choice made by the author of a diagram or document. Sometimes the choice is personal preference or local convention, or sometimes it's just to avoid duplication if a given variable is already in use for something else.

No matter what variable name is used, all electric potential differences are treated the same way for analysis (Ohm's law, Kirchhoff's law, etc.).

Do you have a particular example where the naming is causing confusion?

 

[Mohamad&Issa]

In ohm's law for a generator:
U=E-r.I
U voltage
E electro motive force
r resistance
I current

And ohm's law for a receiver
U=e+r.I
e back electro motive force

 

[gneill]

In ohm's law for a generator:
U=E-r.I
U voltage
E electro motive force
r resistance
I current

And ohm's law for a receiver
U=e+r.I
e back electro motive force

The U,E, and e are representing different potentials in a generator/motor situation. It seems that the author has decided to use U for the "line" potential, e for the back-emf created in the motor's windings (inductance), and E for the potential developed across a generator's windings. The naming convention is designed to help you keep track of what the values represent "in the real world".

The figures in your text might show the inductor potentials as dependent voltage supplies.

 

[Nickie]

Sure, I would be happy to explain the difference between e/E and U (voltage) in Ohm's Law.

First, let's define Ohm's Law. It is a fundamental principle in physics that describes the relationship between voltage, current, and resistance in an electrical circuit. It states that the current (I) flowing through a conductor is directly proportional to the voltage (V) and inversely proportional to the resistance (R), expressed mathematically as I = V/R.

Now, let's break down the different variables in this equation. The lowercase letter "e" is often used to represent the electromotive force (EMF) or the voltage of a source, such as a battery or generator. It is the force that drives the flow of electric charge through a circuit. On the other hand, the uppercase letter "E" represents the total voltage in a circuit, which includes both the EMF and the voltage drops across any resistors in the circuit. So, while e represents the voltage of a specific source, E represents the overall voltage in the entire circuit.

The letter "U" is often used to represent the voltage drop across a specific component in a circuit. In other words, it is the difference in voltage between two points in the circuit. This can be thought of as the amount of energy lost as the electric charge flows through a resistor. In a simple circuit with only one resistor, the voltage drop (U) would be equal to the voltage (V) of the source, but in more complex circuits with multiple resistors, the voltage drop will be different at different points in the circuit.

To summarize, e/E represents the voltage of a specific source or the total voltage in a circuit, while U represents the voltage drop across a specific component in the circuit. I hope this explanation helps clarify the difference between these variables in Ohm's Law.