Electrical grounding and alternating current

In summary, the purpose of grounding households with an Earth wire is to provide a path for electrons to flow to the ground in order to protect appliances. This is necessary because even with alternating current, there is still movement of electrons and the ground acts as a source or sink for these electrons. The Earth wire carries current both away from and back to the appliance, and its function is not to physically transport electrons but rather to protect against potential hazards.
  • #1
Jimmy87
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When households are said to be grounded using an Earth wire, electrons are supposed to flow to the ground because the ground is at zero volts. For example, if your the live wire touches the metal casing of your toaster then the Earth wire takes the current to ground. But isn't a lot of household current alternating? Therefore, how would current flow to ground because with alternating current there is no net movement of charge?

With another example, what would specifically kill you if your feet were on the ground but your hands were touching an overhead cable (you would need to be tall I know). Again, no charge would flow through you specifically as it would be alternating. Would it be the ions in your body which kill you as they would be shaking back and forth due to the alternating voltage?

Also, why is the ground considered to be a source or sink for electrons - wouldn't the ground have to be a conductor to have free electrons?

Thank you for any help!
 
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  • #2
Jimmy87 said:
Therefore, how would current flow to ground because with alternating current there is no net movement of charge?
I'm not sure why you think that is true, but suppose child is playing on a swing, and you step in front of the swing so it hits you. Would you argue that you won't get hurt by the impact, because there is no net movement of the swing, it only alternates between one direction and the other?
 
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An excellent discussion of AC wiring practices, and the function of each wire - the focus is on safety:
http://amasci.com/amateur/whygnd.html

Ask if you have further questions after studying this.
 
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  • #4
AlephZero said:
I'm not sure why you think that is true, but suppose child is playing on a swing, and you step in front of the swing so it hits you. Would you argue that you won't get hurt by the impact, because there is no net movement of the swing, it only alternates between one direction and the other?

Thanks for the replies. From books I have read they say that there is no net movement of electrons in a wire carrying alternating current, therefore how can an Earth wire carry current away from a faulty appliance in the house?
 
  • #5
OK, maybe the use of language isn't very precise and that is confusing you. Half the time, the Earth wire is carrying current away from the faulty appliance. The other half of the time, it is carrying current back to the appliance.

Actually, even the idea of "carrying current" is misleading, because individual electrons in the wire only move back and forth by a few millimeters at most. Nothing physically moves from the appliance all the way to the ground and back again, 50 or 60 times a second. When the appliance is working normally, nothing moves all the way from the power station to your house either.
 
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  • #6
AlephZero said:
Half the time, the Earth wire is carrying current away from the faulty appliance. The other half of the time, it is carrying current back to the appliance.

i have read that earthing is done not for return path of current,but only for protection of equipments.
"carrying current back to appliance" is done in grounding!
 

1. What is electrical grounding and why is it important?

Electrical grounding is a safety measure that involves connecting an electrical circuit or device to the Earth's surface. This is done by using a grounding rod or wire. It is important because it helps prevent electric shocks and fires by providing a path for excess electricity to flow into the ground.

2. How does electrical grounding work?

Electrical grounding works by creating a low resistance path for electricity to flow into the ground. This is achieved by connecting the electrical circuit to a grounding rod, which is buried deep in the ground. When there is excess electricity in the circuit, it will flow through the grounding rod and into the ground, instead of causing harm to people or equipment.

3. What is alternating current (AC) and how is it different from direct current (DC)?

Alternating current (AC) is an electrical current that changes direction periodically. This is in contrast to direct current (DC), which flows in only one direction. AC is the type of electricity used in most homes and businesses, while DC is commonly used in batteries and electronic devices.

4. What are the benefits of using AC over DC?

AC has several advantages over DC. One of the main benefits is that AC can be easily converted to different voltages using a transformer, making it more efficient for long-distance transmission. AC also allows for the use of simpler and more reliable devices, as well as the ability to power multiple devices from the same source.

5. How does an electrical circuit handle AC?

An electrical circuit handles AC by using devices such as transformers and capacitors to convert and control the flow of electricity. These devices can step up or step down the voltage, as well as filter out unwanted frequencies. Additionally, most electrical devices are designed to work with AC, as it is the most commonly used type of electricity in the world.

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