Understanding Parallel Resistance: Why Total Resistance is Smaller

[jsmith613]

why is total resistance smaller than the value of the smallest reistor in a parallel cicuit

 

[lalbatros]

Because a current will go through each resistance.

 

[jsmith613]

Because a current will go through each resistance.

so why is current shared?

 

[lalbatros]

If you have a 9 Volts battery, and you connect a 1 Ohm resitance to it, you will get a 1 Ampère current flowing through the resistance.

Now connect a second resistance to this same plug.
You will have a current of 1 Ampère in this second resistance, for the same reason.
But there will still be 1 Ampère flowing through the first resistance.

Therefore, this battery will supply a total flow of current of 2 Ampères.

 

[jsmith613]

If you have a 9 Volts battery, and you connect a 1 Ohm resitance to it, you will get a 1 Ampère current flowing through the resistance.

Now connect a second resistance to this same plug.
You will have a current of 1 Ampère in this second resistance, for the same reason.
But there will still be 1 Ampère flowing through the first resistance.

Therefore, this battery will supply a total flow of current of 2 Ampères.

this does not answer my question.
Why in a parallel circuit is current shared

thanks

 

[RocketSci5KN]

Current will travel through all available resistive paths given a voltage differential. The amount of current is dictated by the resistance of each path. To answer 'why', it's because the individual electrons travel according to the local electric field they encounter.

 

[lalbatros]

jsmith613,

What do you mean by "shared" ?
Do you mean "added" maybe?
Do you mean "Why in a parallel circuit is current added" ?

If this is your question, this is easy to understand.

Imagine a large tank of water hanging above your head.
Drill one hole through the this thank and assume you get 10 liters/minute flowing on you.
Now, drill a second hole, same size.
You will get the same amount flowing through this second hole: 10 liters/minutes.
Since I assume you are under these two holes, I can conclude you get a shower of 20 liters/minutes.
These two holes provide you with a bigger shower made of two parallel flows.
The flows are added and you will pay water for the total.

Try now to imagine how you could translate the two restances in series in the same analogy.
It is really the same: water or electrons, gravitational force or electrical force.
But do not shower with electrons, that's dangerous !

Michel

 

[jsmith613]

jsmith613,

What do you mean by "shared" ?
Do you mean "added" maybe?
Do you mean "Why in a parallel circuit is current added" ?

If this is your question, this is easy to understand.

Imagine a large tank of water hanging above your head.
Drill one hole through the this thank and assume you get 10 liters/minute flowing on you.
Now, drill a second hole, same size.
You will get the same amount flowing through this second hole: 10 liters/minutes.
Since I assume you are under these two holes, I can conclude you get a shower of 20 liters/minutes.
These two holes provide you with a bigger shower made of two parallel flows.
The flows are added and you will pay water for the total.

Try now to imagine how you could translate the two restances in series in the same analogy.
It is really the same: water or electrons, gravitational force or electrical force.
But do not shower with electrons, that's dangerous !

Michel

If I took a battery and placed in a series circuit placing in JUST an ammeter it would state the current.

If I took an idenital battery and placed it in a parallel cictui placing JUST an ammeter on each branch then the total current equals that of the first circuit.

What I am asking is why does this happen?

 

[Dale]

Conservation of charge. No electrons are created nor destroyed and are only moved around the circuit.

 

[mishrashubham]

Current can be described as the amount of electrical charge passing through a point per unit time in a circuit. So let us imagine you have a simple series circuit with one battery, one resistor and a switch. So you close the switch and current begins to flow (since the circuit is closed now). Let's imagine that 10 electrons begin their journey together from the battery through the wire and let them pass through a given point in that circuit in 1 second. That gives us a current of 10 electron charge units/second (this is just a unit that I made up for the sake of explanation). So they happily travel through the wire and come back to the other terminal of the battery.

Now let us replace the circuit with a parallel one where the equivalent resistance is the same as in the one before (i.e. if the total resistance in the entire series circuit was 1 ohm, the total in the parallel one is also 1 ohm). Let this be a parallel circuit having two resistors. Now again the same 10 electrons begin their journey. However they encounter a split in the paths that they see ahead of them. So some go one way and some the other. Let us assume that 3 go through path no.1 and 7 through path no.2 each having a resistor of its own (the value of the resistance of the individual resistors need not be the same). So now, path no.2 has a current equal to 7 electron charge units/sec, while path no.1 has current which equals 3 electron charge units/sec (since the electrons split from the group while traveling at the same speed). Here we see that adding the currents gives us the original value of current that we measured before the split.

 

[jsmith613]

Thanks