Magnetism help please :)

[Timtasticle]

Hi, I'm having trouble with some physics questions, help would be greatly appreciated

72kW of power is available from a generator, at 240V AC, for transmission to consumers in a town some distance from the generator. The transmission lines over which the power is transmitted have a total resistance of 2.0 ohms.

1. How much power is lost if the power is transmitted at 240V AC?

2. What would be the potential at the end of the transmission lines?

3. Would the townspeople be able to use normal 240V electrical appliances? Why?

4. How much power would be lost if, instead, the voltage was stepped up by a transformer at the generator to 22kV?

5. What would be the voltage at the town if the power was transmitted at 22kV?

Cheers.

[onur369]

1: P=IV, we know that the powerloss- I^2R, we need to find I, thus we do I=P/V => 72000/240 = 300
we then imply the Ploss= I^2 R formula, 300^2 x 2 =180000W. BE CAREFUL sometimes resistance is giving and sometimes total resistance.

Thanks b^3

[b^3]

quick question, how did you get R of the power lines to be 0.5 ohm?

[onur369]

Woopss, misread the question
edited.

[b^3]

Thats how I was working it out, but then we have lost more power than we have begun with?

[onur369]

Thus it will never make it(obviously), a transformer is required. Step up I presume, reasoning : to increase the voltage travelling through the wires and decreasing the current.

Correct me if I am wrong.

[Lasercookie]

I am 100% sure that the answer of 180,000W is correct.

Edit: Thought this question looked familiar. It's from the area of study review in the Nelson book. The worked solutions had a note on it:"Please note: This is beyond the total power produced by the power generator."

I guess that's the purpose of the next question, to force people to realise that, as the potential would be 0. The next few introduce the step-up transformer that Onur mentioned.

[b^3]

I am 100% sure that the answer of 180,000W is correct.

How can we lose 180,000W when only 72,000W are provided? The voltage drop across the wires is going to be the whole 240V.
Seen the edit.

[Lasercookie]

I am 100% sure that the answer of 180,000W is correct.

How can we lose 180,000W when only 72,000W are provided? The voltage drop across the wires is going to be the whole 240V.

That's the idea. No potential is delivered, which gives you the answer to the next question.

It's really just describing a situation over a few questions. The area of study review questions are meant to be exam style, so that's why they don't split it up into 1a 1b etc.

[b^3]

Is there any way of getting a couple of questions out of the Heineman or Nelson books because out school uses Jacaranda, and to put it trufully, its a piece of S***!

EDIT: That would be without breaking any rules or actually buying the book.

[onur369]

If you have the Jacaranda, we can possibly email each other the books :p