Please help (electric shock/Electro static/charge)

  • Thread starter Josh123
  • Start date
In summary, please try to stick to one forum. Thanks.In summary, Thomas was crawling around on the rug. When he reached for a metal truck, a prominent spark lasting 5mmsec appeared between his fingertip and the object. His fingertip was about 2 mm from his toy. His finger burnt (the area of the burned region was of 10^-4 m^2) On that day, the air was cold and dry causing it to become conducting when the electric field reached 3*10^6 N/C. My question is, how you I determine the charge on the child's fingertip? How do I estimate the resistance of the dry air between the toy truck
  • #1
Josh123
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here's a problem that I am currently working on. I know the theory, but I'm not quite sure how to start this particular problem. Here are the values given:

"Thomas was crawling around on the rug. When he reached for a metal truck, a prominent spark lasting 5mmsec appeared between his fingertip and the object. His fingertip was about 2 mm from his toy. His finger burnt (the area of the burned region was of 10^-4 m^2)

On that day, the air was cold and dry causing it to become conducting when the electric field reached 3*10^6 N/C."

My question is, how you I determine the charge on the child's fingertip?
How do I estimate the resistance of the dry air between the toy
truck and the child's fingertip? (I just would like to know how to start this problem.. you don't have to do the entire thing)

Thank you in advance
 
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  • #2
Well you know the field reached 3*10^6N/C, and you know the radius (2mm). I don't know what "5mmsec" is though. I can't think of anything beyond that.
 
  • #3
I'm about at the same place as you. I also know that 3*10^6N/C = 3*10^6 V/m ... but I have no idea what to do with the area or even the distance
 
  • #4
[tex] q_1q_2 = \frac{Fr^2}{k} [/tex], and your unit conversion won't get you anywhere.

What unit are you covering in class?
 
  • #5
It's not exactly a unit. It's a comprehensive assessment that combines several units.
 
  • #6
If you can find the charge, then you can find the current by the relationship between charge and current. With that and ohm's law I would imagine you can find the resistance.
 
  • #7
The thing is, to find the charge, I need the force... to find the force, I need "k" which I don't know
 
  • #8
[tex] k = \frac{1}{4pi\epsilon_{air}} [/tex]

How would you find the charge with that?
 
  • #9
If Eo = 8.85 x 10-12 C2/N-m2, then k= 9.0 * 10^9

I know that E=kq/(r^2)

meaning q=1*10^-9 C

Make sense?
 
  • #10
If what I did in reply #9 correct:

now that I have the charge: 1*10^-9
and the time intervale 0.005 sec

then the current should be 0.0000002 A

Can you tell me if I am on the right track?
 
  • #11
I guess #9 makes sense. Then the current would be

[tex]\frac{10^{-9}/}{(5x10^{-6})} \mbox{ which should be } 0.2 x 10^{-3} [/tex] assuming that "5mmsec" = 5 microseconds.
 
  • #12
I think I should be ok now and I'll be able to work out the other 10 questions associated to that problem. Thank you so much for your help
 
  • #13
You should probably wait around for a more complete and thorough answer.
 
  • #14
ok.. You mean I should wait for someone else?
 
  • #15
Yeah, also that dielectric should be a little less than 8.85x10^-12, since it is in air, so your k value should be a bit less.
 
  • #16
By the way, you wouldn't happen to know if there is a purpose for the area:

"the area of the burned region was of 10^-4 m^2"
 
  • #17
Yeah Claude Mille replied to your post in the General Physics forum, check it out.

Please avoid posting in more than one forum.
 

1. What should I do if I experience an electric shock?

If you experience an electric shock, the first step is to seek medical attention if necessary. If the shock was mild, you can check for any burns or injuries. It is important to also identify the source of the shock and make sure it has been turned off or unplugged before attempting to touch or move it.

2. How do I prevent electric shocks?

To prevent electric shocks, make sure to follow proper safety guidelines and precautions when handling electrical equipment. This includes not using water near electrical outlets, using insulated tools, and making sure cords and wires are not damaged. It is also important to have regular maintenance and inspections of electrical systems to identify potential hazards.

3. What is electrostatic discharge (ESD)?

Electrostatic discharge (ESD) is the sudden flow of electricity between two objects with different charges. This can occur when there is a build-up of static electricity on a person's body and it is discharged when they touch a conductive object, such as a metal doorknob. ESD can also occur in electronic devices, causing damage if not properly protected.

4. How can I protect myself from electrostatic discharge?

To protect yourself from electrostatic discharge, it is important to wear appropriate personal protective equipment (PPE) when working with electronic devices. This can include wearing an anti-static wrist strap or using an anti-static mat. It is also important to ground yourself by touching a grounded object before handling sensitive equipment.

5. What is the difference between an electric shock and electrostatic discharge?

An electric shock occurs when a person comes into contact with a source of electricity, such as an outlet or wire. Electrostatic discharge, on the other hand, is the sudden flow of electricity between two objects with different charges. While both can be dangerous, electrostatic discharge is usually less severe and can be prevented with proper precautions, while electric shocks can be more serious and require immediate medical attention.

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