Final answer:
The maximum load that a 15 ampere duplex receptacle on a general purpose branch circuit can support is 12 amps, due to 80% safety regulation. An 1800-W toaster, a 1400-W appliance, and a 75-W lamp together exceed this limit and will blow a 15-A fuse.
Step-by-step explanation:
The largest cord and plug connected load that can be supported by a 15 ampere duplex receptacle on a general purpose 15 or 20 amp branch circuit is 12 amps. This is based on the safety regulation that limits continuous use to only 80% of the breaker's current capacity. In a 120-V circuit, an 1800-W toaster would draw 15 amps, a 1400-W speaker or electric frying pan would draw approximately 11.67 amps, and a 75-W lamp would draw around 0.625 amps. Adding these up will give you the total current drawn by the devices when they are in parallel.
If we combine an 1800-V toaster and a 1400-W appliance with a 75-W lamp into a 15-A circuit, the total would exceed the 15 amps. Specifically, it would be 15 + 11.67 + 0.625 = 27.295 amps, which would indeed blow the 15-A fuse. Therefore, this combination of devices cannot be supported by a single 15-A circuit and safety practices would need to be followed to redistribute the load or use a circuit with a higher amperage rating.