Effects of Wire Length

[Happy_Jock]

Hello Folks

I have quite a few circuits I would like to activate from a distance say, in a room at the other end of the house for example.

One thing that i have no idea of is how the length of wires effect the working of a circuit. by this I mean for example..

If I have a circuit in the front of the house and want to run 2 long wires from the power supply and put a switch on the end, would a long switch wire effect its capability in the circuit.

or a better way of putting it do circuits loose power over long lengths of wire and does the diameter of the wire make a difference, by long im talking around 15-20 meters

any help would be much appreciated cheers

[pebe]

Hi H_J,
Any wire has a resistance, and the resistance is higher if the wire is long or of small diameter. Whether it affects the circuit depends on what current the circuit takes.

You can consider your power supply as a voltage source feeding the wire and your circuit in series. So the voltage available from your power supply will be split between the wire and your circuit according to the resistance of each.

For instance, if your wire resistance is 10ohms and the resistance of your circuit is 20 ohms and the voltage is 6V, then 2V will be lost in the wire and there will only be 4V available at your circuit. On the other hand, if your circuit is 100K then the voltage 'lost' in the wire will be negligible. If you are referring to the door sensor in the 555 timer in your other thread, then the length of wire won't affect it.