Limiting the Current?

📌 CONCEPT: The melting point of a fuse wire can be reduced by lowering the power dissipated in it without changing its resistance.

📐 RULE / FORMULA: According to the formula P = VI, we can reduce the power dissipated in the fuse wire by either decreasing the voltage across it or the current through it.

💡 WORKED EXAMPLE: In this case, we can reduce the voltage across the fuse wire from 12V to a lower value. For instance, if we reduce the voltage to 6V, the power dissipated in the fuse wire will be reduced by a factor of 2, thus reducing its melting point. This can be achieved by adding a resistor in series with the fuse wire, which will divide the applied voltage and reduce the voltage across the fuse wire.

⚠️ COMMON MISTAKE: Students often think that the melting point of a fuse wire can be reduced only by changing its resistance, which is not the case. By altering the circuit configuration, the power dissipated in the fuse wire can be significantly reduced without changing its resistance.