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I am confused whether Voltage depends on current or the vice versa. I always thought that the vice versa was correct. I tried to find the answers of some of my other conceptual doubts on the web but I was not able to understand the answers as people were saying things beyond school level. But the answers made me confused about the question about $V$ & $I$ mentioned above. Can you please tell which one is correct and why?

Also, please tell me why it is officially stated that $H = I^2RT$ not $VIT$.

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  • $\begingroup$ Have you asked your teacher? $\endgroup$
    – Bob D
    Commented Feb 7, 2022 at 18:26
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    $\begingroup$ "Also, please tell me why it is officially stated that $H=I^2 Rt$, not 𝑉𝐼𝑇." I wouldn't say "officially". There are plenty of Physics textbooks where $Q=VIt$ is given as the primary formula. $Q=I^2Rt$ is a useful form for engineers calculating power dissipation in current-carrying wires. $\endgroup$
    – Philip Wood
    Commented Feb 7, 2022 at 19:04

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Ohm's law, like many (most?) physical laws, does not involve the idea of cause and effect.

I admit that I usually think of V as causing I, but an electronics engineer might put a resistor in a current-carrying circuit in order to produce a pd which can be applied across (say) a voltmeter. The current causes a voltage drop across the resistor!

I don't think there's any right or wrong here.

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    $\begingroup$ I believe that Ernst Mach (after whom Mach numbers are named) claimed that "There is no cause nor effect in nature. Nature simply is. $\endgroup$
    – Philip Wood
    Commented Feb 7, 2022 at 18:54
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I am confused whether Voltage depends on current or the vice versa. I always thought that the vice versa was correct.

Both are true, but you have to know where the voltage and current are being measured to determine the dependence.

Also, please tell me why it is officially stated that $H = I^2Rt$ not $VIt$.

Heat is only dissipated in resistance. For example, if the voltage $V$ and current $I$ are for an ideal capacitor or ideal inductor, there is no heating ($H=0$). Only the in phase components of voltage and current result in heating. So, for heating in an ac circuit, it would be

$$H=V_{rms}I_{rms}t \cos\theta$$

Where $\theta$ is the phase angle between the voltage and current and $rms$ is the root means square value of the current and voltage. For a purely resistive component, $\theta=90^0$, $\cos\theta=1$ and then $H=V_{rms}I_{rms}t$.

Hope this helps.

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They both depend on each other.If you have the IV diagram of a circuit element you can find the current for some voltage across the element and you can find the voltage for some current through the element.

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  • $\begingroup$ Don't forget various devices that have multiple operating regimes such that there are several possible currents at a given voltage (or vice versa), depending on how one gets there... $\endgroup$
    – Jon Custer
    Commented Feb 7, 2022 at 20:20
  • $\begingroup$ Yes that is correct (tunnel diodes,thyristors) $\endgroup$
    – Jun Seo-He
    Commented Feb 7, 2022 at 21:00

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