Why should a 5-ampere fuse never be replaced with a 20-ampere fuse?

Replacing a 5-ampere fuse with a 20-ampere fuse poses a significant safety risk because the primary function of a fuse is to protect the circuit from excessive current. If a circuit is designed to operate safely with a maximum of 5 amperes, using a fuse with a higher rating such as 20 amperes means that the fuse will not blow in the event of a fault that causes the current to exceed this limit.

This could lead to the wiring and components of the circuit being subjected to current levels that they are not designed to handle. Over time, excessive current can generate heat, which may result in insulation failure or even electrical fires.

While other factors like the power supply ripple may be affected and larger fuses may blow due to other conditions, the critical point focuses on the danger of allowing excessive current to flow unchecked, which is why choosing a fuse that correctly matches the circuit's specifications is essential for safety.