DC generator question -- what is happening at no load?

In summary, the conversation discusses the concept of no load in a d.c. generator. It is explained that at no load, the voltage (V) is equal to the generated voltage (E), while the resistance element is disregarded as it does not cause a voltage drop. The relationship between armature current and load current is also mentioned, with the armature current approaching zero at no load condition. The concept of multiplication by zero is also highlighted as a key factor in understanding no load.
  • #1
dave pallamino
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0
In the case of a d.c. generator, if V=E–IaRa when current flows through the armature, why does V = E at no load?
Why does the resistance element become disregarded at no load? Is this because the resistance can't cause the voltage to drop at no load?
 
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  • #2
How is the armature current related to the load current? What can you say about the armature current under no load condition?

If you are having a hard time visualizing "no load". Then imagine a resistance load and you start increasing the resistance. When you get to the order of a Megohm (like what a voltmeter may have), how much current is through the armature, and what is the votage approaching?
 
  • #3
dave pallamino said:
In the case of a d.c. generator, if V=E–IaRa when current flows through the armature, why does V = E at no load?

Your question makes no sense. In that equation, what is the value of V when Ia=0?
 
  • #4
dave pallamino said:
V=E–IaRa

Have you taken first year algebra ?

dave pallamino said:
Why does the resistance element become disregarded at no load?

Is multiplication by zero 'disregarded" ?

dave pallamino said:
Is this because the resistance can't cause the voltage to drop at no load?
Bravo !
Most anything when multiplied by zero yields a zero result.
:smile:

Always make your words and your math come into agreement.
It's important to form that habit because
our minds will believe word constructs that are physically impossible
and that's why they call math "the language of science" .
:oldwink:
old jim
 
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  • #5
dave pallamino said:
Why does the resistance element become disregarded at no load? Is this because the resistance can't cause the voltage to drop at no load?
Yes!
Correct!
You got it!
Good insight!

Carry on with your studies, you passed the first exam.

Cheers,
Tom
 
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1. What is a DC generator?

A DC generator is a device that converts mechanical energy into electrical energy. It is based on the principle of electromagnetic induction, where a magnetic field is rotated within a coil of wire to generate an electric current.

2. What is meant by "no load" in a DC generator?

No load refers to the condition where the generator is not connected to any external circuit or load. In this state, the generator is still producing an output voltage, but there is no current flowing through the circuit.

3. What happens at no load in a DC generator?

At no load, the generator produces a voltage known as the "open circuit voltage". This voltage is the maximum voltage that the generator can produce and is equal to the product of the number of turns in the coil, the strength of the magnetic field, and the speed of rotation.

4. Why is it important to consider the no load condition in a DC generator?

The no load condition is important because it helps determine the performance and efficiency of the generator. It also allows for the measurement of the open circuit voltage, which is a crucial parameter in designing and operating a DC generator.

5. How does the no load voltage in a DC generator vary with speed?

The no load voltage in a DC generator is directly proportional to the speed of rotation. This means that as the speed increases, the no load voltage also increases. This relationship is known as the "generator law" and is an important factor in understanding and controlling the output of a DC generator.

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