What is the required circuit protection for appliances wired at 120 volts using No. 12 wire?

The correct choice is 20 ampere fuse or circuit breaker because appliances wired with No. 12 wire are typically rated to handle a maximum load of 20 amps. This wire gauge is commonly used for circuits that support moderate power usage, providing an adequate level of safety without risking overheating or electrical failure. The National Electrical Code (NEC) specifies that for No. 12 copper wire, the appropriate circuit protection should be set at 20 amps to ensure that the circuit can safely conduct the necessary current for typical household appliances while providing protection against overloads. Using a circuit breaker or fuse rated above 20 amps could lead to overheating and increase the risk of electrical fires, as the wire may not be able to handle the excess current safely.