# Investigating Fuses: Understanding Why Fuses Melt

• O_oSam
In summary, fuses melt when the current passing through them becomes too high, causing them to heat up and eventually reach their melting point. The electrical resistivity, thermal conductivity, and thermal expansion of the fuse material all play a role in its ability to protect the electrical circuit.
O_oSam
I have just started a Physics project which I have already missed the deadline for >_<

I have a very minimal set of results, I basically took a power supply>smoothing unit and put them in a circuit with a component holder and two resistors (in parrallel so I didnt blow the ammeter) and took readings.

Was wondering if I could get some helpful information etc. on fuses. Can anyone give me a detailed explanation of why fuses melt, I was hoping to tie in Electrical resistivity [I'm aware it changes as fuse heats] and possible thermal conductivity?

Does the thermal expansion of a wire have any relevance?

Thanks

Sam

Fuses are designed to protect electrical circuits from excessive current. When too much current passes through a fuse, it will heat up and eventually melt. The melting point of the fuse depends on its material composition, but is typically around 125-150°C. This melting point is lower than the temperature at which most electrical components would be damaged by an overcurrent, so it acts as a protective device.The electrical resistivity of the fuse material increases with temperature, meaning that the resistance of the fuse also increases with temperature. As the resistance of the fuse increases, the current flowing through it decreases, thus limiting the amount of heat generated by the fuse. Thermal conductivity becomes important as the fuse heats up, because it determines how quickly the heat energy is transferred away from the fuse. If the thermal conductivity is too low, then the heat energy will build up more quickly and cause the fuse to melt faster. The thermal expansion of the wire also affects the fuse's performance, as the wire itself will expand when it gets hot and this can affect the contact between the wire and the fuse.

## 1. What is a fuse and how does it work?

A fuse is a safety device that is designed to protect electrical circuits from overloading and overheating. It works by melting or breaking when too much current flows through it, interrupting the circuit and preventing damage to the connected devices.

## 2. Why do fuses melt?

Fuses melt when they are exposed to excessive current. When the current exceeds the fuse's rating, the resistance of the fuse wire increases, causing it to heat up and eventually melt. This is a safety mechanism that protects the circuit from overheating and prevents potential fires.

## 3. How can I determine the right fuse size for my application?

The right fuse size depends on the maximum current that your circuit can handle. You can determine this by calculating the total amperage of all the devices connected to the circuit. Choose a fuse with a slightly higher rating than this calculated value to ensure it can handle any temporary surges in current.

## 4. Can a fuse be reused after it has melted?

No, a fuse cannot be reused once it has melted. Once a fuse has blown, it must be replaced with a new one. Attempting to reuse a melted fuse can be dangerous and may result in further damage to the circuit.

## 5. Are there any alternatives to fuses?

Yes, there are alternative safety devices such as circuit breakers and surge protectors. These devices function similarly to fuses, but they can be reset or turned back on after they have tripped. However, fuses are still commonly used as they are more affordable and reliable for protecting against overloading and overheating.

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