Can the potential inside a metallic cavity electrocute someone?

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Discussion Overview

The discussion revolves around the potential inside a metallic cavity and whether it can electrocute someone. Participants explore concepts related to electric charge, voltage, and the conditions under which electric shock may occur, particularly in the context of conductive materials and their configurations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question the assumption that there is no charge on the inner surface of a metallic cavity, suggesting that metals can easily acquire charge.
  • One participant clarifies that inside a conductive sphere, the voltage is zero at all points referenced to the sphere, but a high voltage relative to an outside point could potentially shock someone if a circuit is completed.
  • Another participant emphasizes that a potential difference is necessary to cause a shock, using the analogy of a bird sitting on a high-potential wire or inside a high-potential cage.
  • A participant introduces the idea of an arbitrary shaped hollow conductor, noting that while the electric field inside would be zero, the potential could still be constant, reinforcing the notion that current, not voltage, is responsible for shocks.
  • Discussion includes details about the thresholds of current that can cause harm, mentioning that the skin's resistance plays a significant role in protecting against electric shock, especially when dry.
  • Participants reiterate that most high voltage demonstration equipment typically does not exceed 1 mA, which is generally considered safe, but caution is advised with experimental equipment.

Areas of Agreement / Disagreement

Participants express differing views on the implications of potential inside a metallic cavity and the conditions under which electric shock may occur. There is no consensus on whether the potential itself can electrocute someone without a potential difference or circuit completion.

Contextual Notes

Some statements rely on specific assumptions about the configuration of conductors and the conditions of the environment, such as the state of the skin (dry or wet) and the nature of the equipment used.

Bhumanyu Arun
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My question was was that though you don't have any charge on the inner surface of a metallic cavity but still there's a potential. Can't that potential electrocute someone?
 
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How you understand that there is no charge?...its metal...and a metal can be charged very easy
 
The OP is a little vague. But I'll assume this is about a conductive, hollow sphere.

Voltage is relative. So inside a conductive sphere (and lacking any other charges) the voltage is zero at all points referenced to the sphere. If the sphere has a high voltage (i.e. lots of charge) referenced to an outside point, it could indeed shock someone, but only someone who completed the circuit to a conductor outside the sphere. That is hard to arrange (impossible if the sphere is totally closed).

Usually this arises with static electric type equipment. Such equipment rarely has enough current to kill people, at least in demonstration type equipment. (It can give a painful shock though. :oldsurprised:) Current kills, not voltage.
 
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Bhumanyu Arun said:
Can't that potential electrocute someone?
Takes a potential difference to shock you.
A bird can sit on a wire that's at high potential . He could also sit inside a cage at high potential. That cage could be a metallic cavity...
 
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jim hardy said:
Takes a potential difference to shock you.
Or "to find that gambling is going on here!" (Casablanca)
 
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:oldsurprised:Sir what you said was fine. And I perfectly agree with that. But what if we have an arbitrary shaped conductor that's hollow but has a definite thickness. Then all the charges will be accumulated on it's surface. Electric field inside it would be 0 but the potential would be constant. If it's a fact that current shocks and not voltage then thank you a lot for getting my doubt clear.
:oldsurprised:
 
It takes about 1 mA across the heart to cause cardiac arrest. However the skin has a resistance of several hundred kΩ when dry (much lower when wet) and current through the body often skips the heart. (Other organs can be affected, and sometimes destroyed at higher current levels as well.) So any amount of current is fine at low voltage levels. Your skin protects you. (Unless your skin is broken. Metallic medical needles used to be a common danger.)

Most high voltage demonstration equipment doesn't exceed the 1 mA level, but often experimental equipment does. Use with caution.
 
Jeff Rosenbury said:
It takes about 1 mA across the heart to cause cardiac arrest. However the skin has a resistance of several hundred kΩ when dry (much lower when wet) and current through the body often skips the heart. (Other organs can be affected, and sometimes destroyed at higher current levels as well.) So any amount of current is fine at low voltage levels. Your skin protects you. (Unless your skin is broken. Metallic medical needles used to be a common danger.)

Most high voltage demonstration equipment doesn't exceed the 1 mA level, but often experimental equipment does. Use with caution.
Thank you sir. It really helpedn
 

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