High and Low Resistance

The more resistance you have in a wire, the more energy you lose (by heating up the wire and its surroundings).

This is therefore a disadvantage for computer cables, transporting electricity, and the wires from the mains outlet to a kettle or electric fire.

The loss of electrical energy, or rather its conversion to heat, is the way the water gets heated (by high resistance wires) in a kettle, or the room gets heated (again by high resistance wires) with an electric fire. Therefore in this case its an advantage.

OK?

The more resistance you have in a wire, the more energy you lose (by heating up the wire and its surroundings).

Not always true. It depends whether the wire or other resistive device is in a series or parallel circuit and what other loads are in the circuit. For example, a resistive load in parallel with another resistive load will lose LESS energy if it has a higher resistance, because more power will be diverted to the other load as resistance increases. Ohm's Law says that

Power (energy used per unit of time) = Volts ² / Resistance

Therefore Energy usage is INVERSELY proportional to Resistance!

Actually, and you can try this yourself if you are careful, a really nicely conducting, low resistance copper wire will immediately get extremely hot when connected to a power source (battery, AC outlet, whatever), while a very high resistance wirewound resistor will just barely get warm.

This is therefore a disadvantage for computer cables, transporting electricity, and the wires from the mains outlet to a kettle or electric fire.

Obviously true. In this case the resistive wire is now in series with some other load which will pull current through the wire no matter what, and since the energy usage (waste heat) is now a function of the current being pulled through it, the equation becomes Power = Current ² x Resistance, or put into electrical symbols, P = I ² x R , so that Power wasted does increase with increased resistance.

The loss of electrical energy, or rather its conversion to heat, is the way the water gets heated (by high resistance wires) in a kettle, or the room gets heated (again by high resistance wires) with an electric fire. Therefore in this case its an advantage.

Not exactly. The high resistance wires are necessary to prevent EXCESSIVE amounts of heat from being produced. As we saw previously, the high resistance actually LIMITS the power loss in producing heat, so that it is stable and manageable. If copper wire were to replace the "high resistance" wire in those heaters, it would get MUCH hotter, at least until the wires burned out or melted, opening, and therefore switching off, the circuit! High resistance wire alloys used for heating are usually more heat resistant as well, melting at a much higher temperature than copper, and so fortunately aid in stabilizing the heating circuit. It is for this reason that you would probably find that a water heater has a much lower resistance than an air heater, since the higher mass of water will conduct heat away much faster, keeping the heating element cooler. An air heater is better insulated by the lighter mass of the surrounding air which can absorb much less heat, and so needs a higher resistance to prevent overheating and burnout.

"Not always true. It depends whether the wire or other resistive device is in a series or parallel circuit and what other loads are in the circuit."

Ok, but in each of the examples given in the original post, the guy's just looking at energy transfer along one path. Maybe (if it was clear that he had the first idea what was going on) I'd have phrased it more like "For a single connection between two points, the higher the resistance of the wire, the greater is the proportion of energy lost".

In this case, I think it would've just put the poor chap off; not good for someone who seems to be just on the first rungs of a very tall ladder.

This really sounds like a homework question.

The first 2 should be obvious if you look at the current flowing thru the wire. The third is the same with 1 extra requirement. The last requires more information (transporting energy covers a VAST range of cables types), how about Weta AAC (it is a valid answer).

Spark plug wires are made with wire as well as carbon-impregnated fibers to increase the resistance, and that's "transporting electricity," and I suppose it could also be "electrical fire."

However, when I want to "transport electricity" I tend to specify copper.

I think the original guest was looking for guidance on types of wire for 4 types of applications and I'm not sure what's meant by kettle or electrical fire??

As for the spark plug wire, that's a specific application of high resistance wire to help from over-loading the hi-tension coil and to minimize radio frequency noise transmission.

Couldn't guess what a kettle is but resistance is NOT good for ( transporting electricity ??) they're ALL transporting electricity.... I hope he meant POWER transmission

And as far as computer cables, I'm guessing that the electrical resistance of let's say CAT-5 wire is less of a "determining variable" in limiting what they say is a nominal 300 foot maximum length for ethernet cables ( you can insert a hub and continue another 300 feet), as is line capacitance and the introduction of electrical noise from a long unshielded antennae, which is what it becomes.

PS: I LOVED your quip "not good for someone who seems to be just on the first rungs of a very tall ladder."