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An office worker uses an immersion heater to warm 250 g of water in a light, covered, insulated cup from 20°C to 100°C in 4.00 minutes. The heater is a Nichrome resistance wire connected to a 120-V power supply. Assume the wire is at 100°C throughout the 4.00-min time interval. Specify a diameter and a length the wire can have. Can it be made from less than 0.5 cm3 of Nichrome?

Verified Answer :

MissPhiladelphia

The amount of energy needed to raise the temperature of 250 g of water from 20 to 100 degree Celsius is
Q = 250 (4.18) (100 - 20)
Q = 83600 J

The power delivered is
P = 83600 / (4(60))
P = 348.33 W

According to the data for a Nichrome wire, the wire gauge for power rating of 348.33 W and 120 V power supply is
23-27 AWG

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