Why does an Electromagnet Vibrate ?

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Discussion Overview

The discussion centers on the phenomenon of vibration experienced by an electromagnet when interacting with iron objects, contrasting this behavior with that of permanent magnets. Participants explore the causes of this vibration, particularly in relation to the type of electrical supply used (AC vs. DC), and seek methods to mitigate the vibrations to achieve a more stable magnetic effect similar to that of permanent magnets.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants note that an iron object near an electromagnet vibrates if the magnetic field is varying, which occurs with pulsing DC or AC, but not with steady DC.
  • It is suggested that pulsing DC can result from a rectifier without filtering, leading to a varying magnetic field and subsequent vibrations.
  • One participant expresses a desire for electromagnets to behave like permanent magnets and asks if there is a method to achieve this.
  • Another participant proposes using pure DC from a battery to reduce vibrations and suggests adding an electrolytic capacitor to smooth the power supply.
  • Concerns are raised about the strength of the electromagnet when using a battery compared to an AC to DC supply, despite the reduced vibrations.
  • Participants discuss the potential for increased voltage and coil turns to enhance the strength of the electromagnet while minimizing vibrations.

Areas of Agreement / Disagreement

Participants generally agree that the type of electrical supply affects the behavior of the electromagnet, particularly regarding vibrations. However, there is no consensus on the optimal solution for achieving the desired stability and strength in the electromagnet's performance.

Contextual Notes

Participants mention various technical details such as voltage, current, and resistance, indicating that practical experimentation is ongoing. There are references to the effects of ripple current and the need for appropriate capacitor ratings, but no definitive solutions are established.

Who May Find This Useful

This discussion may be of interest to individuals exploring electromagnet design, electrical engineering, and those seeking to understand the practical implications of different power supplies on electromagnetic behavior.

viks505
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Why does an Electromagnet Vibrate ?

whenever any iron plate or steel spoon is placed near permanent magnet(not of very high strength) it gets attracted towards it and when it is removed from it it removes easily without any vibration effects.

but if the same thing is performed with electromagnets then we experience a vibration in the spoon both during attraction and during removal of spoon from the field. Also a light humming sound is also there.

why does this vibration happens ??
is there any way to remove this vibration effect in case of electromagnets and let it behave like permanent magnets?

also if AC supply is used in electromagnets(in place of DC supply) then this vibration effect and humming sound is more.

what is the reason behind this phenomenon??
 
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An iron object held near an electromagnet will vibrate if the field from the electromagnet is varying.

This will not occur if the electromagnet is getting steady DC as from a battery but it will happen if the electromagnet is getting pulsing DC, or AC.

It will get pulsing DC if the output is taken directly from a rectifier without any filtering.

Like this:

500px-Halfwave.rectifier.en.png


You can see how the voltage is varying in both the AC input and the pulsing DC output and either of these will result in a varying magnetic field if applied to an electromagnet, so you would get vibration.
 


vk6kro said:
An iron object held near an electromagnet will vibrate if the field from the electromagnet is varying.

This will not occur if the electromagnet is getting steady DC as from a battery but it will happen if the electromagnet is getting pulsing DC, or AC.

It will get pulsing DC if the output is taken directly from a rectifier without any filtering.

Like this:

500px-Halfwave.rectifier.en.png


You can see how the voltage is varying in both the AC input and the pulsing DC output and either of these will result in a varying magnetic field if applied to an electromagnet, so you would get vibration.



yes you are right (this is what principle says) but as u take the iron piece towards the field or if you touch the piece magnetically attached their is a kinda vibration along with humming sound (just give it a try practically) in case of electromagnets but the same is not present in case of permanent magnet.

i think it's coz of generated flux but not sure.

i just want both of them to behave in same manner...is there any known method
 


i just want both of them to behave in same manner...is there any known method


Yes, you would have to run the electromagnet from pure DC, not pulsing DC.

If the electromagnet would work on 12 volts, you could just connect it to a car battery.

Or, you may be able to smooth the power supply by adding an electrolytic capacitor across the electromagnet.
These have to be connected the right way around (+ve marking to the +ve supply) and the actual capacitor would have to be chosen to suit the electromagnet.

Do you know what voltage it runs on and how much resistance it has, or how much current it uses?
 


viks505 said:
yes you are right (this is what principle says) but as u take the iron piece towards the field or if you touch the piece magnetically attached their is a kinda vibration along with humming sound (just give it a try practically) in case of electromagnets but the same is not present in case of permanent magnet.

i think it's coz of generated flux but not sure.

i just want both of them to behave in same manner...is there any known method

An electromagnet will behave the same as a magnet only when you power the electromagnet from a true DC source, such as a battery. If it is powered from a simple home-made DC power supply, then you're apparently getting some "ripple" current into the electromagnet - a portion of the AC waveform is still present at the output of the power supply. This time-varying current is what is causing the time-varying magnetic field that you feel. Adding a very large capacitor to the output of the power supply will reduce, but not eliminate, the ripple. A high quality electronically-regulated power supply can come much closer to an ideal DC source, but a battery is simpler and cheaper.
 


fin i tried the way said by using true DC Supply through a battery.

it did worked, the vibration was lesser as compared to AC converted to DC supply but in this case the strength was weaker.

AC to DC source 12 V, 3 Amps logically 36 watts i.e at max i can draw 3 amps @ 12 V from it.

DC battery 12 V 500 mAh

coil resistance 40 ohms

mathematically it should draw 0.3 Amps from either of the sources for producing the field then why am i finding weaker strength.

this should not happen theoretically but practically i am finding it.

m going to giv a try via capacitor arrangement...in this possibly the vibration must dampen without reducing the strength.
 


Do you have a voltmeter? Check the voltage from the power supply.
It is possible that that power supply is delivering more than 12 volts average because there is not much current flowing.

If it is giving an average of, say, 15 volts, the peak value of the pulses coming out of it will be about 21 volts. If you put a capacitor across the output, the voltage will rise to around 21 volts as well as being smoother.
This will certainly make your electromagnet more powerful. The current in it will rise to about 0.5 amps.
Check that it doesn't get too hot. It will be dissipating about 11 watts, which could make it get quite hot.

The capacitor should be in the range of 1000 uF to 4700 uF and rated for 40 volts.
 


vk6kro said:
Do you have a voltmeter? Check the voltage from the power supply.
It is possible that that power supply is delivering more than 12 volts average because there is not much current flowing.

If it is giving an average of, say, 15 volts, the peak value of the pulses coming out of it will be about 21 volts. If you put a capacitor across the output, the voltage will rise to around 21 volts as well as being smoother.
This will certainly make your electromagnet more powerful. The current in it will rise to about 0.5 amps.
Check that it doesn't get too hot. It will be dissipating about 11 watts, which could make it get quite hot.

The capacitor should be in the range of 1000 uF to 4700 uF and rated for 40 volts.

yeah finally i got it ... minimal vibration and humming sound. though the strength of the magnet wasn't so strong but still it worked.
i think i must increase the no. of turns of the coil along with voltage of the source for more stronger electromagnet.

thanx anyways
 


thanks guys for ur responses
 

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