I always wondered what they use for ground when they are zapping people. Does it just go to the bed frame and out the ground wire the bed is plugged into?
There is no „ground“ in that sense. For a current to flow, you have to create a connection between the source anode and kathode (e.g. + and - of a battery).
You can think of the defibrillator as a battery with a very small but powerful charge. You close the circle by touching both pads to the body. The current will flow through one pad into the body, through the heart and „restart“ it and from there into the other pad. No current leaves this system (=goes into „ground“), it goes back into the defibrillator where the loop is closed.
Why do you get a shock from touching a power cable then, you ask? Without touching another pole and thereby closing the circle? (Note: power cables are AC but for simplification, above DC example can be applied)
This is because for our power stations, the ground is acting as a pole, the current can flow through the ground back to it and thereby close the loop. Therefore, you can reduce the risk of a shock by using boots with thick rubber soles - the rubber acts as an insulator.
Btw, „ground“ is an often misunderstood term. Voltage is the difference between the electric potential of two points in a system. What is often called ground, is the common reference potential.
As powerlines use the actual ground as reference potential, „ground“ has become the defacto name for that - but it’s just a point of reference and can be of any potential. I could measure a voltage (=difference) between the ground of two different systems
Nah. Defibrillators use direct current. Unless they are covered in salt water, there is no reason for the electricity to go anywhere other than in a relatively straight line
If you have two resistors in parallel the current doesn’t just flow through one resistor. You will get shocked. That’s why you yell “clear” before juicing them.
No. You yell clear before defibrillation because of hypothetical risk. The likelihood that a person actually received a significant shock is tremendously low, and even lower if they are wearing gloves.
As a side note, you do not yell clear before juicing them. You charge the defibrillator while continuing to give cpr, and then once it is charged, you clear, analyse the rhythm, and if it is shockable, ensure everyone is clear and deliver the shock. This protocol is to minimise the amount of time the arrested patient goes without chest compressions.
Electricity doesn’t immediately know where to go. It is true that it will always take the shortest path to ground, as soon as it finds that route. This is extremely simplified.
What? No. Electricity takes all conductive paths through a circuit simultaneously, with a current in inverse proportion to the path resistance. Ground means nothing unless it somehow makes up a part of the circuit - it is neither a “sink” nor “zero” for electricity. It’s just dirt.
Electricity always needs somewhere to go. Generally you can refer to where it goes, as a “Ground” I said “This is extremely simplified” for a reason.
I don’t actually understand what you’re trying to say, all I was saying is that Electricity is indeed going to take all possible paths, until it finds the one with the least resistance, which is what I believe you said just in a different way. You are a part of that circuit for a very miniscule, brief second, upon adding yourself (touch).
A battery (or transformer secondary) has two terminals - neither is “ground”, and electricity will flow between them if a circuit is formed.
Often, one terminal of a battery or transformer is connected to a ground stake, so it’s possible for ground to become part of the circuit. But ground is not any kind of natural destination for electricity. (Other than lightning, which is a result of a charge forming between the earth and the clouds)
it doesn’t “find” the path of least resistance. It takes (flows along) all possible paths simultaneously. If you connect two wires in parallel between the terminals of a battery, one of which is thick (resistance) and one of which is thin (high resistance), current will flow along both.
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I always wondered what they use for ground when they are zapping people. Does it just go to the bed frame and out the ground wire the bed is plugged into?
There is no „ground“ in that sense. For a current to flow, you have to create a connection between the source anode and kathode (e.g. + and - of a battery).
You can think of the defibrillator as a battery with a very small but powerful charge. You close the circle by touching both pads to the body. The current will flow through one pad into the body, through the heart and „restart“ it and from there into the other pad. No current leaves this system (=goes into „ground“), it goes back into the defibrillator where the loop is closed.
Why do you get a shock from touching a power cable then, you ask? Without touching another pole and thereby closing the circle? (Note: power cables are AC but for simplification, above DC example can be applied)
This is because for our power stations, the ground is acting as a pole, the current can flow through the ground back to it and thereby close the loop. Therefore, you can reduce the risk of a shock by using boots with thick rubber soles - the rubber acts as an insulator.
Btw, „ground“ is an often misunderstood term. Voltage is the difference between the electric potential of two points in a system. What is often called ground, is the common reference potential.
As powerlines use the actual ground as reference potential, „ground“ has become the defacto name for that - but it’s just a point of reference and can be of any potential. I could measure a voltage (=difference) between the ground of two different systems
Called “sympathy asystole”
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Nah. Defibrillators use direct current. Unless they are covered in salt water, there is no reason for the electricity to go anywhere other than in a relatively straight line
If you have two resistors in parallel the current doesn’t just flow through one resistor. You will get shocked. That’s why you yell “clear” before juicing them.
No. You yell clear before defibrillation because of hypothetical risk. The likelihood that a person actually received a significant shock is tremendously low, and even lower if they are wearing gloves.
As a side note, you do not yell clear before juicing them. You charge the defibrillator while continuing to give cpr, and then once it is charged, you clear, analyse the rhythm, and if it is shockable, ensure everyone is clear and deliver the shock. This protocol is to minimise the amount of time the arrested patient goes without chest compressions.
TIL
Don’t upvote bad information, people.
Electricity doesn’t immediately know where to go. It is true that it will always take the shortest path to ground, as soon as it finds that route. This is extremely simplified.
What? No. Electricity takes all conductive paths through a circuit simultaneously, with a current in inverse proportion to the path resistance. Ground means nothing unless it somehow makes up a part of the circuit - it is neither a “sink” nor “zero” for electricity. It’s just dirt.
https://pubmed.ncbi.nlm.nih.gov/10593226/
Electricity always needs somewhere to go. Generally you can refer to where it goes, as a “Ground” I said “This is extremely simplified” for a reason.
I don’t actually understand what you’re trying to say, all I was saying is that Electricity is indeed going to take all possible paths, until it finds the one with the least resistance, which is what I believe you said just in a different way. You are a part of that circuit for a very miniscule, brief second, upon adding yourself (touch).
A battery (or transformer secondary) has two terminals - neither is “ground”, and electricity will flow between them if a circuit is formed.
Often, one terminal of a battery or transformer is connected to a ground stake, so it’s possible for ground to become part of the circuit. But ground is not any kind of natural destination for electricity. (Other than lightning, which is a result of a charge forming between the earth and the clouds)
it doesn’t “find” the path of least resistance. It takes (flows along) all possible paths simultaneously. If you connect two wires in parallel between the terminals of a battery, one of which is thick (resistance) and one of which is thin (high resistance), current will flow along both.
You are taking my extremely simple analogy and making it complex. Good job!
Slow-mo video of a lightning strike can demonstrate that
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