# Why does the current increase when the potential differene stays constant?

• xllx
In summary, the conversation discusses the relationship between temperature, resistance, current, and voltage in a specimen being tested. It is established that the resistance of a metal wire increases with temperature, but the current through the wire also increases despite a constant voltage being applied. The conversation also clarifies that the specimen does not contain any switches or fuses, and is just a piece of metal wire. The question of how the current increases with a constant voltage and increasing resistance is also addressed.
xllx
A specimen has a potential difference applied, which remains constant throughout. The current through the specimen increases substantially though. Why does it increase?

Is this to do with the temperature of the wire increasing and so resistance decreases and the current therefore increases. But the potential difference won't be affected as it is constant in voltage.

Is this right at all? Or totally wrong?

Many Thanks!

You're saying the temperature dependency backwards. If the temp of a metal wire increases then the resistance would increase.

To say that you're testing a specimen isn't really enough information. It doesn't sound clear whether the object under test might contain any switches or fuses or diodes, etc., or is able to be stretched into a new shape, or it's chemical composition is being altered, etc. Is it known to be simply a metal wire of constant dimensions? Are you expected to determine whether or not it is a metal wire?

Last edited:
mikelepore said:
To say that you're testing a specimen isn't really enough information. It doesn't sound clear whether the object under test might contain any switches or fuses or diodes, etc., or is able to be stretched into a new shape, or it's chemical composition is being altered, etc. Is it known to be simply a metal wire of constant dimensions? Are you expected to determine whether or not it is a metal wire?

Sorry, no it doesn't contain any switches etc. but is just a piece of metal wire.

So as the temperature in the wire increases, the resistance also increases. But how does this make the current increase if the voltage is constant?

Thanks.

## 1. Why does the current increase when the potential difference stays constant?

This phenomenon is known as Ohm's Law, which states that the current flowing through a conductor is directly proportional to the potential difference (voltage) applied to it, as long as the temperature and other physical conditions remain constant. Therefore, as the potential difference stays constant, an increase in current can only be explained by a decrease in resistance.

## 2. Does this mean that the current will continue to increase indefinitely?

No, the current will eventually reach a maximum value as the resistance of the conductor cannot decrease indefinitely. Once the resistance reaches its minimum value, the current will remain constant even if the potential difference increases further.

## 3. How does the resistance affect the relationship between current and potential difference?

The resistance of a conductor is inversely proportional to the current, meaning that as resistance decreases, current increases. This can be seen in Ohm's Law as R (resistance) is in the denominator of the equation I (current) = V (potential difference) / R. Therefore, a decrease in resistance leads to an increase in current, even when the potential difference remains constant.

## 4. Are there any materials that do not follow this relationship between current and potential difference?

Yes, there are materials known as non-ohmic conductors that do not follow Ohm's Law. These materials have a varying resistance depending on the potential difference applied to them, causing the current to change even when the potential difference remains constant.

## 5. How is this concept applied in real-life situations?

Ohm's Law is used extensively in electrical engineering and is the basis for the design of electric circuits. By understanding the relationship between current, potential difference, and resistance, engineers can accurately predict the behavior of a circuit and ensure that the components can handle the expected current at a given potential difference.

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