# Thicker wires for lower voltage? (1 Viewer)

#### m_wahwah

##### Member
In transformers, if the output voltage is lower than the input, it has a thicker wire. Why?

The question popped up in a paper I was doing, the answers say:
"Output has lower voltage but higher current so needs thicker wire."

I mentioned the higher current, but said that the wire provides a higher resistance to counter the current and prevent power loss. Is that wrong?

#### kawaiipotato

##### Well-Known Member
I think it's because a thicker wire would provide less resistance, and so it would reduce the energy loss due to heat

#### rand_althor

##### Active Member
In transformers, if the output voltage is lower than the input, it has a thicker wire. Why?

The question popped up in a paper I was doing, the answers say:
"Output has lower voltage but higher current so needs thicker wire."

I mentioned the higher current, but said that the wire provides a higher resistance to counter the current and prevent power loss. Is that wrong?
$\bg_white P_{loss}=I^2R$. If we have a higher resistance, then we would have a greater power loss. So ideally, you'd want a low resistance for a low power loss.

If the secondary coil has a lower voltage output, then it will have a higher current flowing through it. From the formula, you can see that a high current will contribute to a greater power loss. Because of this, we need to decrease resistance to decrease power loss. As kawaiipotato has said, this is achieved by using a thicker wire. This is because resistance is inversely proportional to the cross-sectional area of the conductor the current is flowing through (greater cross-sectional area=lower resistance). So there needs to be a thicker wire in the secondary coil of a step-down transformer as it decreases resistance and thus power loss, allowing for a more energy efficient transfer of electricity.

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#### m_wahwah

##### Member
$\bg_white P_{loss}=I^2R$. If we have a higher resistance, then we would have a greater power loss. So ideally, you'd want a low resistance for a low power loss.

If the secondary coil has a lower voltage output, then it will have a higher current flowing through it. From the formula, you can see that a high current will contribute to a greater power loss. Because of this, we need to decrease resistance to decrease power loss. As kawaiipotato has said, this is achieved by using a thicker wire. This is because resistance is inversely proportional to the cross-sectional area of the conductor the current is flowing through (greater cross-sectional area=lower resistance). So there needs to be a thicker wire in the secondary coil of a step-down transformer as it decreases resistance and thus power loss, allowing for a more energy efficient transfer of electricity.
Great explanation, thanks. I had the right idea in my mind but got it mixed around somehow.

#### anomalousdecay

$\bg_white P_{loss}=I^2R$. If we have a higher resistance, then we would have a greater power loss. So ideally, you'd want a low resistance for a low power loss.

If the secondary coil has a lower voltage output, then it will have a higher current flowing through it. From the formula, you can see that a high current will contribute to a greater power loss. Because of this, we need to decrease resistance to decrease power loss. As kawaiipotato has said, this is achieved by using a thicker wire. This is because resistance is inversely proportional to the cross-sectional area of the conductor the current is flowing through (greater cross-sectional area=lower resistance). So there needs to be a thicker wire in the secondary coil of a step-down transformer as it decreases resistance and thus power loss, allowing for a more energy efficient transfer of electricity.
This is not the only reason behind the requirement of thicker wires.

Wires of different thickness will have different impedances (or resistance in DC as you have been taught in HSC).

The impedance can be large if the wire is too thin. For all wiring, there is a maximum amount of current allowable due to their internal impedance (Ohm's law), before they begin to increase in resistance by themselves and turn non-linear, essentially becoming non-ohmic.

So if this happens, then an increased power loss occurs. Not only that; you will likely fatigue the wiring and it will burn out the transformer.

Wires have specific ratings for maximum current due to their internal impedance (which is related to their thickness!). If you expect a higher current (example for a step down transformer), then it would be good practice to use thicker wiring on the secondary side to prevent the issues I mentioned above.

If you are keen, have a read through the different types of wiring and have a look at their datasheets. For example, take a look at different internationally used systems to distinguish between wires https://en.wikipedia.org/wiki/Wire_gauge

#### DepressedPenguino

##### Active Member
Lol all i know is that thicker wires would provide lower resistance