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Ohms law

salesm21

To anyone who can help,

I have been recently wondering about something rather simple. Why is it in ohms law does R=V/I & I=V/R? This means that voltage is proportional to both resistance and current? I know the more voltage you have the more energy is given to each coloumb of charge but why is it that when 1 volt of energy is in 1 C of charge is there 1 ohm?

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  • Hi Mitchell,

     

    Let's imagine that we have a perfect source of 10 volts with no internal resistance. What ohms law does is give us a formula for calculating the current in a circuit if we know the resistance of that circuit or the resistance of a circuit if we know the current. You can not think of Ohm's law outside the context of a circuit. If we have the 10 volt supply and we put an ammeter in the circuit and we measure 5 amps of current we can use the Ohms law to determine that the circuit has 2 Ohms of resistance. If on the other hand we put a 6 Ohm resistor across the 10 volts we will find that 1.66 Amps are flowing if we were to measure it. Let me know if I misunderstood your question.

     

    John

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  • Hi Mitchell,

     

    Let's imagine that we have a perfect source of 10 volts with no internal resistance. What ohms law does is give us a formula for calculating the current in a circuit if we know the resistance of that circuit or the resistance of a circuit if we know the current. You can not think of Ohm's law outside the context of a circuit. If we have the 10 volt supply and we put an ammeter in the circuit and we measure 5 amps of current we can use the Ohms law to determine that the circuit has 2 Ohms of resistance. If on the other hand we put a 6 Ohm resistor across the 10 volts we will find that 1.66 Amps are flowing if we were to measure it. Let me know if I misunderstood your question.

     

    John

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  • in reply to jw0752

    John,

    So I think you did. You reasoning was that ohms law is a group of mathematical formulas that are used to help us calculate circuit quantities as well as understand and quantify relationships between different electrical phenomenon. So your saying I have to look at Volt/current & resistance in separate ways then as a whole?

  • in reply to salesm21

    Hi Mitchell,

    In any given circuit there is a physical relationship between Voltage, Resistance, and Current. Ohm's law models this relationship mathematically. Theoretically it is possible to have a voltage without a current if there is an infinite resistance. We can not have a current without a voltage. Different materials become resistances when they become part of a circuit and convert the energy of the electron flow into heat. Since I didn't understand your last question I have tried to rephrase my previous response.

    John