# Charge of the body

Discussion in 'General Electronics Chat' started by @hacker, Jan 15, 2015.

1. ### @hacker Thread Starter New Member

Nov 30, 2014
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Is the human body neutral? If yes then why does the speaker make noise, when its jack touch any human body?

2. ### ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
You could say a conductive copper wire used as an aerial is 'neutral', but it picks up electrical signals ie: 'noise', radio waves etc.

The human body is just a bag of salty water, as you may know salty water is conductive, so your body acts like a receiving aerial picking any local EM radiation.

Touching an amplifier input just completes the circuit path to ground for the EM signals, which get amplified.

OK.?
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3. ### ScottWang Moderator

Aug 23, 2012
5,478
864
The human body including capacitance, resistance and inductance.
If the speaker just putting at the end of the amplifier then it won't affect anything, sometimes if wiring the wrong phase of the speaker, if this situation then you just exchange the wire of speaker will be ok, if not then the wire of speaker could be picking up the 60hz or noise.

4. ### ErnieM AAC Fanatic!

Apr 24, 2011
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If you have ever touched something metal on a cool winters day after walking across a carpet you should know the human body can hold a substantial static charge.

5. ### @hacker Thread Starter New Member

Nov 30, 2014
10
0

Thanks for the reply...i got this answer from one of my friend that in the input circuit of audio amplifier we usually have 2 input gate: non-inverting and inverting. normally, the non-inverting input has been connected to GND, so inverting input will receive the input signal. the human body is negatively charged, when we touch to inverting input, the output signal will be raised, then this signal go through power amplifier and go to speaker, make a noise. if we connect the inverting input to ground, the noise will be louder.
Is that true??

6. ### ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
No,
An stereo audio amp has two inputs, Left and Right channels, the inputs are not inverting and non inverting .

The human body or any other body can be negatively or positively charged with respect to Earth or any other body.

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