Magnetic field and generator power output

In summary, the conversation discusses the relationship between magnetic field, frequency, and power output in a generator. The equations used show that frequency is inversely proportional to magnetic field, and decreasing the magnetic field could potentially increase the frequency and therefore the power output of the generator. However, it is important to consider other factors such as maintaining a constant torque and the source of the current.
  • #1
dansmith170
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TL;DR Summary
Could decreasing the magnetic field increase a generator's power output?
Hi,

I am confused about whether decreasing the magnetic field used for a generator could increase the generator's power output.

I used four equations:

1. Torque = Force x radius
2. Torque = NIAB (N = number of turns, I = current, A = area of armature, B = magnetic field).
3. emf = NAB(2*pi*f) (emf = electromotive force, f = frequency of rotation of armature.
4. I = emf / R (R = resistance)

Using these equations, I found that frequency is inversely proportional to magnetic field ("f" is proportional to "1/B^2"). If that is the case, then decreasing magnetic field should actually increase frequency, correct?

A generator should produce more power when the frequency is greater. Well then, a generator with lower magnetic field, provided that it has greater frequency, should produce more power.

I get the feeling that I made a mistake somewhere in my math or reasoning, would someone please help me out on this?

Thanks.

Citations to sources for relevant equations:
https://courses.lumenlearning.com/suny-physics/chapter/23-5-electric-generators/
http://spiff.rit.edu/classes/phys213/lectures/amp/amp_long.html
 
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  • #2
To keep a constant emf, if the B field is lower, the frequency has to be increased. The frequency compensates for a low B field in order to maintain an emf. The power is not greater.
 
  • #3
osilmag said:
To keep a constant emf, if the B field is lower, the frequency has to be increased. The frequency compensates for a low B field in order to maintain an emf. The power is not greater.
osilmag, thanks for your response. Suppose I do not want to keep a constant emf, but I do want to keep a constant torque. In that case, would lowering the B field mean increasing frequency (f) in a way that increases total power output of the generator?
 
  • #4
If you wanted a constant torque when your B field lowered, your current would have to increase. That has to come from your current source. Is the current in equation 2 the same as in equation 4?
 
Last edited:
  • #5
osilmag said:
If you wanted a constant torque when your B field lowered, your current would have to increase. That has to come from your current source. Is the current in equation 2 the same as in equation 4?
Yeah, same current (I) in both equations.

The current source is, I think, from the mechanical force that is spinning the generator's armature (maybe it is a wind-powered generator). In that case, the generator's armature spin, measured in frequency (f) should determine the current (I) magnitude.

In other words, given that current (I) is proportional to (B) times (f) (see equations 3 and 4), if I decrease (B) but (I) increases, then (f) must increase by a greater amount than (B) has decreased by.

Agree?
 
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  • #6
Agree
 

1. What is a magnetic field?

A magnetic field is a region in space where a magnetic force can be detected. It is created by moving electric charges, such as the flow of electricity through a wire.

2. How does a magnetic field affect generator power output?

A magnetic field is essential for the operation of a generator. When a conductor, such as a wire, moves through a magnetic field, it induces an electric current in the wire. This current is what generates the power output of the generator.

3. What factors can influence the strength of a magnetic field?

The strength of a magnetic field can be influenced by the distance from the source of the field, the size and shape of the magnet, and the material it is made of. Additionally, the strength of a magnetic field can be increased by increasing the flow of electricity through a wire or by using a stronger magnet.

4. How can a magnetic field be measured?

A magnetic field can be measured using a device called a magnetometer. This device uses sensors to detect the strength and direction of a magnetic field. The strength of a magnetic field is typically measured in units of Tesla (T) or Gauss (G).

5. How can the power output of a generator be increased?

The power output of a generator can be increased by increasing the strength of the magnetic field, increasing the speed at which the conductor moves through the field, or by using a larger or more efficient generator design. Additionally, using stronger and more conductive materials for the wire can also increase the power output.

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