A very basic thing in electrical circuits that has confused me for weeks

[davesparks]

@davesparks - yes , you are right. I just confused it entirely. A short ryt after the load ( i-e positive side wire with the negative side wire will bypass the load and the fuse will blow so no current passes through load.

But a short before the load that is on negative side still will cause fires ( damages to wire ) because there is no fuse in that side ?

You can't have a short on the negative side

 

[Hawk]

It's a negative ?

 

[Hawk]

http://www.howacarworks.com/basics/how-car-electrical-systems-work

 

[Darkwood]

@davesparks - yes , you are right. I just confused it entirely. A short ryt after the load ( i-e positive side wire with the negative side wire will bypass the load and the fuse will blow so no current passes through load.

But a short before the load that is on negative side still will cause fires ( damages to wire ) because there is no fuse in that side ?

A short to what - after the load any cabling etc are already at chassis potential as they will either connect direct to the chassis or another common point at the same potential as the chassis, if the fuse has blown feeding the load then the wiring to the load is also potential free to the chassis/ground.

Its simpler to draw it out and position your fuse and loads etc and then you can visualise it better.

 

[Lucien Nunes]

There is one scenario that single-pole fusing doesn't protect against: If a fused, non-grounded conductor of a high-current circuit short-circuits to a smaller unfused grounded conductor, then there is a risk that the fuse in larger circuit won't prevent damage to the smaller one. This is a remote probability though and is usually discounted in general installation work, due to the general advantages of single-pole fusing.

 

[DuaneMHunt1976]

I'm guessing, that the person has read that flow isn't positive to negative but the other way around.
So figures the fuses should be at the state of the flow than the end.

I can't remember kirchoff laws.just what you put in comes out.

 

[thescript]

In the picture below :
What If point A touches point B ? Wont it be a short circuit ? Will it not bypass the fuse making its role as null ?
In my opinion the only role that a fuse would play is when point B touches point C ?

I dont know If my concern is valid in the first place but It is something that has made me sleepless for last couple of days.
I hope it would be easier for you people to correct me .. Thanks alot

 

[Lucien Nunes]

Wherever you put the fuse, there will always be a point upstream of it that isn't protected. That's why you put each fuse as near to the beginning of the circuit that it protects as possible, usually in the first half inch! In your drawing, you would physically locate it at the battery terminal, so that point A doesn't really exist - it's only the battery terminal itself.

 

[Richard Burns]

The usual arrangement for fuses is to be close to the positive supply and enclosed so that there is a little chance of any short circuit occurring in the circuit it is meant to protect prior to the fuse.


EDIT: As Lucien Nunes has just posted before me!

 

[thescript]

Now I am all cleared.
Thanks everyone
It was really helpful

 

[YoungScud]

The current will still pass through the fuse. It's a circuit,and with that circular nature, no current will flow.