Induced EMF in a half vs. whole ferrite toroid

In summary, the individual had a question about magnetic materials and conducted an experiment with a ferrite toroid and a current carrying wire. They measured a potential difference between the coil terminals and expected a higher induced voltage when the toroid was cut in half, but instead measured nearly zero. They asked for an explanation and were directed to read about current transformers and how they work. It was explained that it is not possible to have a broken or partial core in a current transformer.
  • #1
GaryLS
2
0
Hello all -

I've stumbled upon what seems to be a pretty basic magnetic materials question that's got me stumped. Maybe one of you can help me figure this out.

I did the following experiment (see figure below):
  • Put a ferrite toroid around a current carrying wire carrying 12 Amps RMS at 120V, 60 Hz.
  • Toroid has a wire coil around it that's wrapped around a small angular section of the toroid
  • Measured 90 mV RMS potential difference between the coil terminals on the voltmeter, which is about what I expected based on what I learned about this problem in college physics
  • Cut the toroid in half, and put the half-toroid with the coil around it right next to the current carrying wire, but in this case measured nearly 0 mV RMS potential difference between the coil terminals
Can anyone explain why I measured nearly zero mV when the toroid was cut in half? Even though the toroid is cut in half, it's still made of ferromagnetic material, so I would have expected the field strength to be boosted inside the half-toroid (by a factor of α, where α is the ferrite's relative permeability), and therefore would have expected to see a much higher induced voltage in the coil. I would have expected to see more like 50 mV RMS in the coil in this case, but not zero.

Thanks in advance for any insight you can provide!

Gary

upload_2017-4-14_15-23-58.png
 
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  • #2
GaryLS said:
Hello all -
......
  • Cut the toroid in half, and put the half-toroid with the coil around it right next to the current carrying wire, but in this case measured nearly 0 mV RMS potential difference between the coil terminals
Can anyone explain why I measured nearly zero mV when the toroid was cut in half? Even though the toroid is cut in half, it's still made of ferromagnetic material, so I would have expected the field strength to be boosted inside the half-toroid (by a factor of α, where α is the ferrite's relative permeability), and therefore would have expected to see a much higher induced voltage in the coil. I would have expected to see more like 50 mV RMS in the coil in this case, but not zero.

Thanks in advance for any insight you can provide!

Gary

do some reading up of current transformers and how they work
here is a link or two to start you off

https://en.wikipedia.org/wiki/Current_transformer

https://www.quora.com/How-do-current-transformers-work

they will explain why you cannot have a broken or only a section od a coreDave
 
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Related to Induced EMF in a half vs. whole ferrite toroid

1. What is induced EMF in a half vs. whole ferrite toroid?

Induced EMF (electromotive force) refers to the voltage generated in a circuit due to a changing magnetic field. In a half ferrite toroid, the magnetic field is only partially passing through the core, while in a whole ferrite toroid, the magnetic field completely encircles the core. This can affect the amount of induced EMF and its direction in the circuit.

2. How does the number of turns in a winding affect induced EMF in a half vs. whole ferrite toroid?

The number of turns in a winding can affect the strength of the magnetic field passing through the core. In a half ferrite toroid, the magnetic field is only passing through a portion of the core, so the number of turns will have a smaller impact on induced EMF compared to a whole ferrite toroid where the magnetic field is passing through the entire core.

3. What materials are used to make ferrite toroids?

Ferrite toroids are typically made from ferrite materials, which are a type of ceramic material made from iron oxide and other metal oxides. These materials have high magnetic permeability, making them ideal for use in electromagnetic applications.

4. How is the magnetic field in a ferrite toroid created?

The magnetic field in a ferrite toroid is created by passing an electric current through a wire wound around the core. This creates a magnetic field that is concentrated within the core, which is then used to induce EMF in a circuit.

5. What are some common applications for ferrite toroids?

Ferrite toroids are commonly used in electronic circuits for filtering, impedance matching, and energy storage. They can also be found in transformers, inductors, and other electronic components. They are also used in various industries such as telecommunications, aerospace, and medical equipment.

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