An immersion heater used to boil water for a single cup of tea plugs into a 120

Question

An immersion heater used to boil water for a single cup of tea plugs into a 120 V outlet and is rated at400 W . Suppose your super-size, super-insulated tea mug contains 400 g of water at a temperature of 13 C. You can ignore the energy needed to raise the temperature of the mug and the heater itself.

Part A

What is the resistance of the heater?

Express your answer to two significant figures and include the appropriate units.

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Part B

How long will this heater take to bring the water to a boil?

Express your answer using two significant figures.

An immersion heater used to boil water for a single cup of tea plugs into a 120 V outlet and is rated at400 W . Suppose your super-size, super-insulated tea mug contains 400 g of water at a temperature of 13 C. You can ignore the energy needed to raise the temperature of the mug and the heater itself.

Part A

What is the resistance of the heater?

Express your answer to two significant figures and include the appropriate units.

SubmitMy AnswersGive Up

Part B

How long will this heater take to bring the water to a boil?

Express your answer using two significant figures.

Explanation / Answer

a) R = V² / P = (120 V)² / 400 W = 36

b) Q = mcT = 0.4 kg x 4,200 J/kg°C x (100°C - 13°C) = 1.4 x 10^5 J

t = Q / P = (1.4 x 10^5 J) / 400 W = 350 s = 5.83 min

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