Why do we need resistors if wires have resistance?

[cscott]

A question I've never had fully answered:-

Why are resistor(s) necessary in a circuit in the sense that wires themselves (in my mind) should have resistance since they constitute material just like resistors themselves?

Thanks

 

[Hootenanny]

A question I've never had fully answered:-

Why is are resistor(s) necessary in a circuit in the sense that wires themselves (in my mind) should have resistance since they constitute material just like resistors themselves?

Thanks

I think what you asking is that shouldn't the wires in a circuit have a resistance?

The answer is of course, yes! All materials (except super conductors) have a resistance and therefore should technically be accounted for in calculations. However, such calculations become tedious and generally, since wires are good conductors the error in ignoring the resistance of the wiring is negligible. There are some cases, such as power lines, where the resistance of the cabling must be taken into account.

 

[cscott]

But doesn't this imply that we add resistors to a circuit just for computational ability?

Can I consider a circuit with a capacitor and a wire taken with capacitance C and and resistance R?

Why can't the resistance of the wire take $$R= \rho \cdot \frac{L}{A}$$ like a "resistor" that we'd typically use?

 

[Nabeshin]

It can be, but this is a ridiculously low resistance in almost all cases. Therefore you're likely to mess up your circuit somehow. When you try to discharge a capacitor through just a wire, you will see sparks fly. Hook just wire up to a battery, and it will heat up very quickly and drain the battery. Resistors serve to regulate the flow of current, not for computational ability.

 

[Andy Resnick]

WIRE = Wicked Infinitesimal Resistance Element.

Sometimes, a wire has sufficient resistance on it's own- a lightbulb filament is an example.

 

[pallidin]

Resistors are necessary in electronic circuits when the value, or amount, of specific resistance to electron flow is needed. This oftentimes exceeds the amount of resistance of a simple "wire"

 

[cscott]

I get it now. Thanks all.