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I'm a stupid high school student trying to understand domestic circuits. I've recently learned about the earth wire which reduces the value of current traveling through a person's body when they touch an appliance with current leakage.

Let us suppose that the live wire with a voltage of 200V is in contact with the body of a metallic refrigerator. An earth wire is connected to its body which transmits current from the metallic body to the ground. A very unfortunate person who comes in contact with the metallic body should experience a shock

Now, the body of the refrigerator is acting like a voltage source with two resistors present in the circuit in parallel. i.e. the person and the earth wire. I've been told that most of the current will pass through the earth wire and the person will not experience a severe shock.

BUT since the voltage between the metallic body and the ground is still 200V and the person is still present as a resistance between the potential difference, so current should still pass through the person despite the earth wire still being there.

(ik i'm going wrong somewhere and this might be a very dumb doubt, so please excuse me) THANKS!

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The voltage will not stay at 200V if you connect it to the ground. In a modern installation, the RCCB will trip, as soon as the ground current is above tens of mA (depending on your local regulations)

If it doesn't trip, as the ground connection resistance is very low, less than 1 ohm, so you would draw much more than 200 A. Which will trip the circuit breakers and/or fuses of most installations, either in your house or on the distribution network side. Or melt the cables (which has the same effect of breaking the circuit) For comparison, UK standard plugs have a 13 A fuse.

But even without that, the voltage across the refrigerator will still drop. To simplify, your circuit is composed of 3 resistances in series:

  1. power source to refrigerator
  2. metallic case of refrigerator
  3. ground connection back to the power source

the resistance of 1 and 3 are not smaller than 2, so it would act like a voltage divider, and you wouldn't see all the voltage on the case itself.

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  • $\begingroup$ Thanks for your response. It means a lot. $\endgroup$
    – banana4147
    Commented Dec 28, 2022 at 15:08
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Hi it may be because that in parallel connection current in the circuit increases so when we try to remove the earth wire the same current Is flowing through the person

I only know this much and this is a good question too

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  • $\begingroup$ Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center. $\endgroup$
    – ZaellixA
    Commented Dec 28, 2022 at 15:47
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You’re absolutely right. You’re not eliminating current travelling through the human body, you’re just reducing it to a harmless level. You’ve actually got tiny currents flowing through your body all the time, because every practical insulator doesn’t have infinite resistance. These currents are so tiny, however, that they’re barely detectable, even with sensitive instruments, and completely irrelevant from a safety perspective.

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  • $\begingroup$ The voltage across the person is still 200V... So how does the current decrease? This is my question. Thanks for your reply! $\endgroup$
    – banana4147
    Commented Dec 28, 2022 at 14:27
  • $\begingroup$ You may think at the human body as a new wire of the circuit, that forms a "closed loop" with the Earth These currents are usually very low. These are dispersed currents that don't flow back to the origin. If you have a residual-current device, this system measure the difference between the current in the two wires of the circuit. If the difference exceeds a threshold, the residual-current devices interrupts the circuit for safety reasons. $\endgroup$
    – basics
    Commented Dec 28, 2022 at 14:32

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