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I=Current, V=Potential Difference, R=Resistance, P=Power(just in case if you don't understand wth I am speaking)

I understand the contradiction between P=VI and Ohm's Law, and I understand about Transformers too, but, my only problem is that, I don't get the idea, how exactly does all of this happen? I mean, look, V inverses to I in calculating power supply, but, why use it, when we already know a relation(R=V/I, as the current travels through electric cables, which undoubtedly possess resistance, so should be able to calculate I), and it only makes it harder to understand, I mean, I watched numerous vids, and googled the stuff, but none of the answers seems to satisfy me, I am looking for a suitable answer that makes me say, "Woah, that was some fire!"

I mean I get so confused, while transferring the power, V inverses to I, but as soon as the same current passes through the step-down Transformer, and gets to the household circuits, it's back to Ohm's Law again(let's assume there are only ohmic conductors), I mean, when I try to co-relate the two, and try to understand this whole massive setup of "transferring power from power plant to houses," I am unable to understand all of this practically, and reading the book doesn:t help me, though I might not have read it so carefully.

I Am In 10th Standard, so simple, answers are very very welcome, though I will try my level best to understand the higher level answers as well

Thanks in advance

Aniket Roy
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2 Answers2

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I imagin a small community using just 200kW of power at 200V with $200,000W=V*I$ you have $I=1000A$ so the resistance of all the stuff is $R=0.1\Omega$ so if the the voltage at the beginning would be 200V too and the wire to the community had resistance $R_w=1\Omega$ the current would be $200V/1,1\Omega=182A$ instead of 1000A and your power would be V=18V. so you should be happy to have a transformer increasing the Voltage in the wire 100 times, so the current in the wire ist only 1/100 of the former. You should not only consider $P=V*I \text{ but also } P=I^2*R or P=V^2/R$. Maybe you can ask your teacher to do an Experiment with 6 V lamp and a wire to the lamp with some resistance larger than the one of the lamp , and then transform the voltage at the beginning to 100V and at the end to 6 V again. than you can really "experience the difference in classroom.

trula
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I wouldn’t worry too much about Ohm’s law since the primary and secondary are separate circuits. Concentrate on the concept of EM induction.

  1. A current creates a magnetic B-field.
  2. A coil creates s stronger field
  3. A changing current creates a changing field
  4. A changing B-field induces a changing current.
  5. More turns of wire give a higher voltage.

Conservation of energy/power cannot generate more power; but can shift the factors iR within the transformer.

Primary coils are exposed to a high voltage to carry power at low current (Ohm’s law) over long distances. They produce the changing magnetic field that floods the secondary coil of a different number of turns in the coils.

  • Fewer turns gives lower voltage
  • More turns gives higher voltage My local utility gets power from a 132 kV supply. That is first reduced to 24 kV entering the city. Next, several sub-stations reduce to 3200 volts. Then, a transformer powers my home at 240 volts. Ultimately I have devices that raise/lower for special uses.

Keep in mind that the ratio of turns in each transformer sets up a new voltage; but energy is drawn through an appliance only when it’s plugged in or drawing current. Then you can apply ohm’s law in that circuit … separate from the other side of the transformer.

Gene
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