Verified answer

Current is Power over Voltage, so 1000/100=10A. Supply current in parallel is the sum of the current drawn by all components in parallel, so in this case, 20 Amperes.

You would ideally use a 22A or 24A breaker but in reality, it would likely be a 32A one.

Edit: Can I point something out here? If you have an MCB rated to trip @20A and you happen to be pulling exactly 20A, what do you think will happen to the MCB?

Lauren,

The total load you have is 2000 watts, to determine the current divide by the voltage to get:

2000/100 = 20 amps. This is the total amount of current the circuit will draw.

Typical circuit breakers at rated at 100% of their marked current level, i.e., a 20 amp circuit breaker, to carry their full marked current with the circuit breaker mounted in free air at 40 degrees C or 104 degrees F.

If this is the condition in which you mount the circuit breaker and you keep the air temperature around the circuit breaker (CB) to 104 degrees F or less, it will successfully supply the 20 amps your circuit will need to operated the toaster and coffee maker.

In the real world, it is more likely your circuit breaker will be mounted in a circuit breaker panel with other circuit breakers. If they have any load on them they will add to the heat around your circuit breaker and thus it may trip at 20 amps of load. This is because the circuit breaker in most homes are thermal devices. They trip due to the heat generated in the CB as it carries load current. If the CB carries 20 amps and continues to heat up due to the heat from near by CBs and thus will trip at 20 amps and not carry your load.

The National Electrical Code (NEC) recognizes this and they specify that any CB in your panel is only to carry 80% of the level stamped on the CB. So your 20 AMP CB is to be rated at 16 amps.

Based on this the NEC would say you need to use a (20 AMP/.8) = 25 amp circuit breaker unless you meet the requirements of operating in free air.

Hope this helps,

Newton1Law

Total power = 1000W (toaster) + 1000W (coffeemaker)

Total Power = 2000W

Watts = volts x amps

Amps = Watts /volts

Amps = 2000/100

Amps = 20 A

The circuit breaker should be 20A

Additional: It's true that in reality you would NOT use a 20 breaker in this sort of circuit; but, something a little higher to give you some leeway otherwise a 20A breaker will trip as soon as the two appliances are on at full power. It always amazes me at the sort of answers people give. At this sort of level you are NOT expected to know about this distinction and 20A would be considered correct at this level of your physics education. Your teacher may mention that a higher breaker will be required in practice;but, I doubt if he/she knows what current ratings the breaker come in and they certainly would not expect you to know that either! After all, the purpose of the question is to get you familiar with the physics equations not to train you as a sparky! So, unless you are training to be an apprentice electrician and your bedtime reading includes the NEC codes and up-to-date IEEE regulations (Lol!), then you are simply not going to know. If ever they want you to make a more informed choice they would always provide you with specifics values and then ask you to select from the list of options provided: 10A, 15A or 25A; in which case, the correct answer would be 25A. Put simply, you don't want an over complicated answer to what is a very simple and basic question.

Your steady-state current is 10A but you need either a higher value breaker or a delayed-action breaker to handle the inrush current.