# Relation between current and resistance

I was knowing that the current is inversely proportional to resistance but recently i read that resistance has effect on voltage only and it doesn't have an effect on current because the current depends on the number of electric charges in motion but voltage is related to the energy of these charges. What is the explanation supporting this

• What does $I=V/R$ tell you? Aug 2 '20 at 21:06
• Isn't R a constant for a material and depends on it's physical properties? Aug 3 '20 at 4:48

resistance is defined as R=U/I, so is it not very good to say: the current is inversely proportional to resistance, if you do not complete your sentence with: if voltage is constant.

The current is directly proportional to the voltage and inversely proportional to the resistance. This means that increasing the voltage will cause the current to increase, while increasing the resistance will cause the current to decrease Conclusion: it depends upon whether voltage is fixed or resistance is fixed

Voltage and current are equally fundamental (the charge itself is even more fundamental; Voltage is the energy per unit charge, current is the rate of change of charge).

• If you apply a given voltage across a resistor, it will cause a given current to flow.

• If you drive a given current through a resistor, it will develop a given voltage across it.

In the context of any given circuit or experiment, either one may be the driver of concern.

Attempts to argue otherwise are just sophistry and playing on words.

Current is directly proportional to voltage. And resistance(R) is the proportionality constant. Hence V=IR

If we double the voltage in a circuit the current in the circuit will double itself (Ohm's law), but the ratio of voltage to current will remain the same .

If voltage is V, let the current in the circuit be I. Hence the ratio of voltage to current will be V/I.

On doubling the voltage, the current in the circuit becomes twice of itself, V'=2V & I'=2I. In this case also the ratio of voltage to current becomes 2V/2I=V/I, same as in the previous case. This ratio is the proportionality constant 'R', that is resistance . Hence we can say current is directly proportional to voltage, but resistance is fixed in the circuit, unless we change it otherwise.

However current is directly proportional to voltage only in the case of ohmic conductors and up to a certain limit*.

In case of non ohmic conductors current is not directly proportional to voltage. That is if we double the voltage, the current need not get doubled . It may get 1.5 or 1.6 etc times of itself , but still in that condition the equation V=IR stands perfect where R is the resistance of the circuit at that time.

• if we make the voltage 1000 times of itself, the current will not become 1000 times of itself, because when current flows in a conductor, heat is generated . This results in increased molecular motion of the conductor , thus the electrons suffer greater collisions and the resistance increases from its original value R to R'.Hence we do not get the current 1000 times its value because it is

1000V/R .....(i), which is equal to 1000(V/R) which equals to 1000I and not

1000V/R'.....(ii) Obviously since R' is greater than R, equation (ii) will be smaller than (i). Hence we obtain a lesser value of I

But here also the equation V=IR stands true, where V is voltage I is current and R is the resistance of the circuit at that time.