(basic question) why is current the same in series connection.

marconi · Mar 4, 2022

Replied in error..................

Pastory · Mar 4, 2022

marconi said:
First, never place any electrical wires in your mouth. Promise me?

The way to look at the circuit you drew is to consider whether a complete circuit is made when you touch one and only one of the wires from the battery. The answer of course is it is not a completed circuit. Therefore the electromotive force of the battery cannot set up and electric field in the wires which would cause electrons to flow from the - end of the battery to the + end of the battery. If no electrons flow then there cannot be an electric shock or sensation.

The answer above becomes not so true as the electromotive force of the battery is increased. This is because even though it may seem a circuit is not completed there may be stray connections through the air gaps for example if the air is moist. Even though the effective resistance of the electrical circuit path through the air gap may be quite high in value, as the electromotive force is increased so does the current since from Ohm's Law the current through a resistor is proportional to the voltage drop across the resistor and inversely proportional to the resistance. The resistance of the path through the gap also reduces as it shortens in distance. Thus there is an emf which when it exists across an air gap will force a current to flow the magnitude of which increases with emf and shortening of the gap. At a high enough emf the air will begin to ionise leading to a corona discharge, sparking or full on arcing.

The situation is made worse when the emf is an alternating current. This is because not only is there an effective resistance path there is also stray capacitance between the ends of the gap. A so-called capacitive current will flow in addition to the current through the stray resistance. One should keep well away from live conductors.

The term neutral only applies to a conductor when it is connected to the earth or ground by an earth electrode. The term neutral means the conductor is 'tied' to the potential of the (local) earth which means there is no potential difference between the neutral conductor and the local earth. If there is no potential difference there can be no current flow through a conducting item connected between the neutral and earth provided that one remains near to the earth electrode. Further away from the electrode other things begin to happen which are beyond your scope for now.

If you use a a figure of 50V for ac or dc as the maximum safe touch voltage in dry conditions you will remain unhurt or alive in most circumstances but this voltage may well be much lower if for example your skin is wet or the water is salty or there is a large surface area in contact across the emf.

These links take you to some articles and introduce the SELV and PELV power supplies used in the UK and Europe.
PELV | PULS - https://www.pulspower.com/uk/support/service/glossary/index/read/pelv/#:~:text=PELV%20(Protective%20Extra%20Low%20Voltage,protection%20must%20still%20be%20provided.
SELV | PULS - https://www.pulspower.com/uk/support/service/glossary/index/read/selv/#:~:text=The%20voltage%20of%20a%20SELV,exceeded%20for%20longer%20than%20200ms.

Alternating Current or Direct Current? | Which is Safer? - https://electricalinstallationservices.co.uk/alternating-current-or-direct-current/

Ohm’s Law (again!) | Electrical Safety | Electronics Textbook - https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/ohms-law-again/

A little intricate explanation, but to cut the story short there are a few more questions.

Why does neutral not carry electricity in large scale circuits (domestic circuits), because basically in simple circuits electrons from negative terminal push electrons in the wire, and why actually does a live wire cause shocks while there is no complete circuit.

An explanation in diagram would be very helpful.

SparkyChick · Mar 4, 2022

Pastory said:
Sorry for some litle question, are you the moderator of this forum?

I am one of the moderators yes

marconi · Mar 6, 2022

Pastory: Good afternoon from London. I have attached something for you to look at and think about. On the left is a generator G supplying a load L via Line and Neutral conductors. The Line is brown and the Neutral is blue in the UK and Europe. The Neutral is connected to the earth via a long copper electrode at the generator. I want you to assume (which is a good assumption) that the earth/ground is a very good conductor so the right hand earth electrode E2 to which the two voltmeters V connect is connected to the electrode E1 at the generator through a resistance which is very small compared to r and R. R is the resistance of the load and r is the resistance of the Line and the Neutral conductors - the same value because they run together and are made of the same type of wire. A current I circulates in the circuit driven by the emf of the generator. The circuit on the right is the electrical 'equivalent' circuit of the real circuit on the left.

What will the voltmeter connected between the Line conductor and earth read ie VL?

What will the voltmeter connected between the Neutral conductor and earth read ie VN?

You ought to be able to right down a value for VL or VN in terms of V, I, r and R. VL and VN are the potentials of the Line and the Neutral conductor with respect to or referred to earth's potential. Earth's electrical potential is assumed to be zero Volts.

It is time you did some analysis ;-)

Enjoy!