transformers

[ssluffy]

POWER SUPPLY ----- STEP UP ----------(transmission lines)---------- STEP DOWN ------ LOAD

can someone clarify
if the load resistance doubles, does:

1. the current in the power supply half?
2. does the overall power half?
3. voltage loss decrease?
4. voltages in the power supply, step up and step down transformers stay the same?

assume that transformers are ideal, only the transmission lines have significant resistance.
thanks.

[Linkage1992]

The current would not be affected.
The power at the first transformer would not be affected, however the power loss in the transmission wires would double according to P= I^2 R
Voltage loss would double according to V = IR.

The voltage in the primary of a step up transformer is smaller than at the secondary, and because of the voltage loss in the wires, the voltage at the primary of the step down will be lower than at the secondary of the step up.

really sorry, i misread your OP...

[ssluffy]

i dont understand why the current would not be affected, when the voltage and power losses double. wouldnt increasing the resistance in the load decrease the current in the load, lowering the power?

[3Xamz]

The current would not be affected.
The power at the first transformer would not be affected, however the power loss in the transmission wires would double according to P= I^2 R
Voltage loss would double according to V = IR.

The voltage in the primary of a step up transformer is smaller than at the secondary, and because of the voltage loss in the wires, the voltage at the primary of the step down will be lower than at the secondary of the step up.

Dude if the load increases, it has to draw more power from the power supply? Energy isn't created out of anywhere. If the load takes in more energy, your power supply better provided it..

[Linkage1992]

oh shit, reading comprehension fail!  I thought the OP was asking about if the resistance in the transmission wires was doubled! 

[lachymm]

The current would not be affected.
The power at the first transformer would not be affected, however the power loss in the transmission wires would double according to P= I^2 R
Voltage loss would double according to V = IR.

The voltage in the primary of a step up transformer is smaller than at the secondary, and because of the voltage loss in the wires, the voltage at the primary of the step down will be lower than at the secondary of the step up.

Dude if the load increases, it has to draw more power from the power supply? Energy isn't created out of anywhere. If the load takes in more energy, your power supply better provided it..

this...

[ssluffy]

>__>

[3Xamz]

I wish I could answer your question ssluffy, but I am unsure myself and don't want to tell you the wrong thing.
So, I hope some wonderful soul comes by and saves us (A)

[Linkage1992]

yeah, me too. too scared to say anything, i'll probably make myself look like an idiot again.

[TyErd]

too much thinking involved.

[ssluffy]

i was thinking:
if resistance increases then that means we connect an extra resistor in series.
thus, current will stay the same. however, voltage would increase, given that V = IR

thus power increases?
current in the primary of the step up transformer increases?
voltage loss increases?

i dont understand :S
 

[waack]

i dont think you have given enough information like is the power still the same at the load or does that have to be the same with the resistance increase

[bblovee]

I think a larger load -> higher current being drawn -> Power being transmitted is fixed, so if more current is being drawn, the transmission voltage decreases according to P=IV -> lower voltage & higher current -> more Ploss. Ploss=I^2R, and more Vloss. Vloss = IR

Assuming the resistance of the transmission cables dont change:
2x Load -> 2x current -> 2x Vloss and (2)^2R= 4x Ploss.

[3Xamz]

^ That's what I was thinking but didn't wanna say anything without clarification

[Juddinator]

Power is the only good thing about Unit 4 physics. IMO the rest is pointless...