Fuses and grounding in a circuit

[sgstudent]

When I ground something, how does the electrons actually flow into the earth? Since it is not a complete circuit whereby electrons flow back into the battery such as in cases like a battery connected to a bulb. I always thought a complete circuit was required so how can the electrons "choose" to flow into the Earth without going back to the source? On another note, if my source has a pd of 10V, will the potential at the bulb be 10V and O st the Earth's point of contact?

When I touch the live or neutral wire, why won't the fuse melt? Is it because I'm taking the V=RI of my body and the circuit around it. So the resistance of me is very high so the I would be very low compared to when before I touch the live? But in that case, won't there be a parallel branch whereby one continue through the main circuit and another through me? So in that case what would be the explanation for this?

Thanks for the help guys!

 

[Loro]

If I understood correctly, you're talking about a situation in which you ground something, e.g. an electrode which is charged, and electrons then just flow into the ground. The difference is that this current is not a steady state current. It's a transient. They just flow out and they're gone. Now to draw a continuous current you need a closed circuit - there has to be a loop, which charges are continuously pumped around.

Regarding the second bit, you're totally correct. Perhaps your resistance is so high that the voltage doesn't even manage to "break down through you". And yes in that other case you would be a parallel branch. But verify yourself, from maths and by intuition, that adding a very high resistance parallel branch, doesn't change the net resistance too much. The extra branch draws a very small current, and effectively doesn't change the currents flowing in the rest of the circuit significantly.

Hope that helps

 

[sgstudent]

If I understood correctly, you're talking about a situation in which you ground something, e.g. an electrode which is charged, and electrons then just flow into the ground. The difference is that this current is not a steady state current. It's a transient. They just flow out and they're gone. Now to draw a continuous current you need a closed circuit - there has to be a loop, which charges are continuously pumped around.

Regarding the second bit, you're totally correct. Perhaps your resistance is so high that the voltage doesn't even manage to "break down through you". And yes in that other case you would be a parallel branch. But verify yourself, from maths and by intuition, that adding a very high resistance parallel branch, doesn't change the net resistance too much. The extra branch draws a very small current, and effectively doesn't change the currents flowing in the rest of the circuit significantly.

Hope that helps

Thanks for the help! It explained a lot to me. But when dealing with grounding cases, how do I determine the effective resistance? Since its not like a normal parallel branch where it goes back to the circuit..

Thanks so much for the help!

 

[Loro]

I would be more clear if you gave a specific example. But whenever you have a grounded node, its potential is defined to be zero. If you have another - its potential is zero too, and basically - they're connected to a common ground node - so they're connected together.

 

[PJC01]

I can provide some clarification on the concepts of fuses and grounding in a circuit.

First, let's talk about grounding. When we ground something, we are essentially providing a path for excess electrical charge to flow into the earth. This is important because it helps to prevent electrical shocks and damage to equipment.

Now, to address your question about the flow of electrons into the earth, it's important to remember that electrons always flow from areas of high potential energy to areas of low potential energy. In the case of grounding, the electrons are flowing from the circuit, which has a high potential energy, to the earth, which has a lower potential energy. This is why the electrons "choose" to flow into the earth rather than back to the source.

In terms of a complete circuit, it is not necessary for the electrons to flow back to the source for grounding to occur. As long as there is a path for the electrons to flow into the earth, grounding can be achieved. This is why grounding rods or metal pipes are often used for grounding, as they provide a direct path for the electrons to flow into the earth.

Now, let's discuss the potential difference (pd) at the bulb and the earth's point of contact. In a circuit, the potential difference is the same at all points in a series circuit. This means that the potential at the bulb would also be 10V, as long as there is no resistance in the circuit. However, if there is resistance in the circuit, the potential difference will decrease as the electrons flow through the circuit.

Moving on to fuses, these are used to protect the circuit from excessive current flow. When you touch the live or neutral wire, the fuse will not melt because your body has a high resistance compared to the wire. This means that the current flowing through your body is limited, and therefore the fuse will not melt. However, as you mentioned, there may be a parallel branch where some current flows through the main circuit and some through your body. This is known as a ground fault and can be dangerous. This is why it's important to have proper grounding in a circuit, to prevent any parallel branches from forming.

In summary, grounding and fuses are important components in a circuit to protect against electrical shocks and damage. Understanding the flow of electrons and potential differences can help us better understand how these components work in a circuit. I hope this helps answer your questions!