- #1

- 202

- 0

...I believe current in inversely proportional to resistance but what about current and voltage. Also, what about voltage and resistance?

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter Air
- Start date

- #1

- 202

- 0

...I believe current in inversely proportional to resistance but what about current and voltage. Also, what about voltage and resistance?

- #2

Hootenanny

Staff Emeritus

Science Advisor

Gold Member

- 9,621

- 6

When we say

...I believe current in inversely proportional to resistance but what about current and voltage. Also, what about voltage and resistance?

[tex]x = k\cdot y[/tex]

Where

[tex]x = \frac{k^\prime}{y}[/tex]

Where

Now taking your example of current and resistance, you are indeed correct to say that current is inversely proportional to resistance because we can re-write Ohm's law thus,

[tex]I = \frac{V}{R}[/tex]

So in this case,

Does that help to clear things up?

- #3

- 202

- 0

When we sayxis proportional toy, this means we can write it in this form,

[tex]x = k\cdot y[/tex]

Wherekis the constant of proportionality. When we sayxis inversely proportional toy, we can write it in this form,

[tex]x = \frac{k^\prime}{y}[/tex]

Wherek'is another constant of proportionality.

Now taking your example of current and resistance, you are indeed correct to say that current is inversely proportional to resistance because we can re-write Ohm's law thus,

[tex]I = \frac{V}{R}[/tex]

So in this case,Vis our constant of proportionality.

Does that help to clear things up?

So is it:

Voltage is proportional to resistance.

Voltage is proportional to current.

- #4

Hootenanny

Staff Emeritus

Science Advisor

Gold Member

- 9,621

- 6

Indeed it is .So is it:

Voltage is proportional to resistance.

Voltage is proportional to current.

- #5

- 202

- 0

When a circuit short-circuits, does that mean current is zero hence resistance is low?

- #6

Hootenanny

Staff Emeritus

Science Advisor

Gold Member

- 9,621

- 6

The resistance is indeed usually low, but that doesn't mean that the current is low, in fact it's quite the opposite. A short-circuit simply means that the current flows along an unintended path. In practise this usually means that a low-impedance connection is made between two points in the circuit that would normally be at difference voltages. Since the resistance is low, this causes a large current to flow across the short.When a circuit short-circuits, does that mean current is zero hence resistance is low?

- #7

- 202

- 0

The resistance is indeed usually low, but that doesn't mean that the current is low, in fact it's quite the opposite. A short-circuit simply means that the current flows along an unintended path. In practise this usually means that a low-impedance connection is made between two points in the circuit that would normally be at difference voltages. Since the resistance is low, this causes a large current to flow across the short.

So, what about current? It's proportional to both so would it be high or low?

- #8

Hootenanny

Staff Emeritus

Science Advisor

Gold Member

- 9,621

- 6

So, what about current? It's proportional to both so would it be high or low?

[tex]I = \frac{V}{R}[/tex]The resistance is indeed usually low, but that doesn't mean that the current is low, in fact it's quite the opposite. A short-circuit simply means that the current flows along an unintended path. In practise this usually means that a low-impedance connection is made between two points in the circuit that would normally be at difference voltages.Since the resistance is low, this causes a large current to flow across the short.

The current is proportional to the voltage (which in this case is constant) and inversely proportional to the resistance, hence a low resistance results in a large current.

- #9

- 202

- 0

[tex]I = \frac{V}{R}[/tex]

The current is proportional to the voltage (which in this case is constant) and inversely proportional to the resistance, hence a low resistance results in a large current.

...And high voltage as it is proportional to current?

- #10

Hootenanny

Staff Emeritus

Science Advisor

Gold Member

- 9,621

- 6

It isn't quite that simple, it would depend on the structure of the circuit....And high voltage as it is proportional to current?

It would perhaps be prudent to mention that the majority of shorts are not Ohmic conductors, since a very large current flows that short (wire) usually heats up very quickly and therefore there is a non-linear relationship between V, R and I.

Last edited:

Share: