company news about Does the fuse have resistance?

The fuse has a resistance value. In fact, even the wire has resistance, but the resistance of the wire is very small (the nature of the conductor). In general circuit calculations, we usually don’t count it, but the resistance of the fuse is obviously larger than the resistance of the equal-length wire. In this way it can play a role in protecting the circuit.

The fuse is marked with "5A 250V", indicating that the maximum current allowed by the fuse is 5A, which is called the rated current; the maximum voltage allowed to pass through is 250V, which is called the rated voltage. If the current or voltage exceeds the rated value, the fuse will blow, breaking the circuit and protecting the consumer (if there is no fuse, the consumer may be burned).

The fuse blows and the principle is Joule's law. Joule's law: The heat generated by the current passing through the conductor is proportional to the square of the current, proportional to the resistance of the conductor, and proportional to the time of electrification. The mathematical expression of Joule's law: Q=I²Rt, and the derived formulas are Q=UIt and Q=U²2/R×t. All the work done by the current in the fuse generates heat, that is, all the electric energy is converted into internal energy. At this time, Q=W. Therefore, when I or U is greater than the rated value, Q becomes larger, so that the fuse cannot dissipate heat in time and overheat, and finally blows.

In general, when the circuit current or voltage exceeds the rated value, the fuse will not blow immediately, because the fuse allows a larger current or voltage value to allow short-term overwork. That is to say, if you find that the current or voltage of the circuit is abnormal, you still have a chance to correct the error, but for accidental errors (such as a short circuit in the main line), the wire may catch fire before the fuse is blown. Take precautions, there is no chance of regret