The iMac is very energy efficient. A typical iMac will draw around 150-200 watts when in use so you can easily connect 8 iMacs to a 20 amp circuit. This would equate to a 80% draw on the circuit. I would not recommend any more than 8. That is assuming nothing else is on that circuit.
You can plug in as many as you want but none of them will work. An "open" circuit is an electrical circuit which is not a complete circuit and therefore electricity will not flow through it. If you mean an unused circuit,which has no load on it, then the answer is 2 ea. 5 amp devices on a 15 amp circuit and 3 ea. 5 amp devices on a 20 amp circuit. The reason for this is that any circuit is not to be "loaded" more than 80% of the OCPD (circuit breaker amperage rating.
A 20-amp circuit can typically support up to 10 receptacles.
A 30 amp circuit can safely support up to 4 outlets.
Up to 12 on a 20 amp circuit. Up to 9 on a 15 amp circuit. But use common sense. If the circuit will be heavily loaded, as in a home office, then do not install that many.
A 32 amp fixture can not be fed from a 20 amp breaker as the breaker will trip every time.
A 15 amp circuit can safely handle up to 1800 watts of power.
Yes, you can use a 15 amp outlet on a 20 amp circuit. The outlet's amp rating should not exceed the circuit's amp rating.
On a 20 amp circuit, it is safe to install up to 13 outlets that are rated for 15 amps each.
No more than 13 maximum on a 20 amp circuit.
Eight on a 15 amp circuit, tweleve on a 20 amp circuit, including the gfci receptacle itself.
80% of the rated circuit. 10 amp circuit is 8 amps, 20 amp circuit is 16 amps, etc.
No, it is not safe to use a 20 amp outlet on a 15 amp circuit as it can overload the circuit and potentially cause a fire hazard. It is important to match the outlet with the circuit's amp rating to ensure safety.