Electromagnetism in my physics class

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Discussion Overview

The discussion revolves around the principles of electromagnetism as they relate to transformers, specifically focusing on their operation with alternating current (AC), the reasons for high voltage transmission, and the role of transformers in delivering power from hydroelectric plants to homes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses curiosity about why transformers require alternating current and the necessity of high voltage for power transmission.
  • Another participant explains that transformers only work with AC, detailing the behavior of current in a transformer when connected to a direct current (DC) source.
  • A participant discusses the relationship between current, voltage, and power loss in transmission lines, emphasizing the importance of high voltage to minimize losses due to resistance.
  • There is a mention of the relationship between changing current and magnetic flux, indicating that steady current does not generate magnetic flux, which is essential for transformer operation.
  • A participant seeks clarification on the operational mechanism of transformers.
  • Another participant provides a link for further understanding of transformers.
  • A participant questions the terminology used to describe the function of the secondary coil in a transformer, suggesting that "stimulates" may not be the best word.
  • One participant confirms the accuracy of the previous statement regarding the primary and secondary coils.

Areas of Agreement / Disagreement

Participants generally agree on the principles of transformer operation and the necessity of AC for their functionality. However, there is no explicit consensus on the terminology used to describe the secondary coil's role.

Contextual Notes

Some participants discuss the behavior of current and voltage in transformers and transmission lines without resolving the underlying assumptions or definitions related to these concepts.

Who May Find This Useful

This discussion may be useful for students learning about electromagnetism, particularly those interested in the practical applications of transformers and power transmission systems.

sp00ky
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Well I was learning bits about Electromagnetism in my physics class and we were learning about transformers and thought it was kind of neat. I was just wondering why transformers use alterneting current and why power must be delivered at such high voltages across transmission lines? Also, how is transformers used in delivering poweer to homes from the hydro-electic power plant?
 
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Transformers will not work with DC, only with AC. If you connect a battery across the terminals of a transformer, the current in the primary will rise linearly with time, due to the inductance of the primary, until eventually the core saturates at which point the current will rise even more quickly, until it becomes limited only by the resistance of the wire. This happens even with no load on the secondary.

When you hook up an alternating voltage to a transformer, it works as intended. Only a small amount of current "circulates" in the circuit due to the inducatance of the primary. Thus if there is no load on the secondary, very little current will flow in the primary either.

Transmission lines work at high voltages to keep the losses due to resistance down. The power loss due to the resistance of the lines is I^2*R. The power carried by a line is V*I. Therefore by making V high and I small, a minimum of power is lost due to resistance for a given amount of power transmitted.
 
The CHANGE of current generate magnetic flux, and the CHANGE of megnetic flux generate voltage...Steady don't generate magnetic flux therefore we need alterneting current...
remember [tex]power=I^2R[/tex] the resistance in the transmission line generate heat, which is a waste of energy, in order to minimize the power loss, we want to keep the current [tex]I[/tex] low.. the only way to do that is make the voltages high [tex]power=IV[/tex], if the power unchange low I implies high V.
 
Oh okay, makes sense. But how do transformers actually operate?
 
oh thanks for that link. Is this right: The primary coil receives alternating current and the secondary coil basically stimulates the potential difference? Dunno if stimulates if the best word for it.
 
yes, basically, you r rite
 

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