1)Energy Efficiency at Home Suppose you have two kettles – a plug-in electrickettle and a stovetop kettle. The electric kettle uses electricity from a natural gas fired powerplant, while you boil water in your stovetop kettle on a natural gas burner. a)Based on the following information, which of these kettles demonstrates a higher energy efficiency (i.e., which is more efficient at using energy from fuel to heat water)? Please calculate the efficiencies of each kettle and express answers as percentages. -The natural gas power plant converts chemical energy of the natural gas to electrical energy with 58% efficiency. -High-voltage power lines from the power plant to your house convey electricity with 92% efficiency. -The electric kettle converts electrical energy to thermal energy in the water with 85% efficiency (the other 15% heats up the kettle itself). -The stove burner converts chemical energy of natural gas to thermal energy with 98% efficiency (the other 2% is light).- The stovetop kettle transfers 35% of the stove’s thermal energy to the water in the kettle. Electric kettle efficiency: .58*.92*.85= 0.45356 = 45% Stovetop kettle efficiency: .98*.35=.343= 34% Electric kettle more efficient b)Based on the following information, how does a 1000W microwave compare to the stovetop and electric kettles in terms of water-heating efficiency? Calculate both electricity-to-heat and overall efficiency (assuming electricity from a natural gas fired power plant). Please express your answer as a percentage. -A 1000W microwave takes 120 seconds to boil 8 oz of water. -The boiling point of water is 100°C, and room temperature water is 20°C -The specific heat of water is 4.186 J/gC c)Electric kettles are quite efficient, but people often use them carelessly and boil more water than they need – while microwaves are typically used to boil the precise amount needed at a time. If the average kettle ends up boiling 2 times as much water as needed, while the microwave boils the exact amount, how does this change efficiencies from parts a and b? Assume that the amount of water boiled does not change how much heat is lost to the kettle itself.
1)Energy Efficiency at Home Suppose you have two kettles – a plug-in electrickettle and a stovetop kettle. The electric kettle uses electricity from a natural gas fired powerplant, while you boil water in your stovetop kettle on a natural gas burner.
a)Based on the following information, which of these kettles demonstrates a higher energy efficiency (i.e., which is more efficient at using energy from fuel to heat water)? Please calculate the efficiencies of each kettle and express answers as percentages.
-The natural gas power plant converts chemical energy of the natural gas to electrical energy with 58% efficiency.
-High-voltage power lines from the power plant to your house convey electricity with 92% efficiency.
-The electric kettle converts electrical energy to thermal energy in the water with 85% efficiency (the other 15% heats up the kettle itself).
-The stove burner converts chemical energy of natural gas to thermal energy with 98% efficiency (the other 2% is light).-
The stovetop kettle transfers 35% of the stove’s thermal energy to the water in the kettle.
Electric kettle efficiency: .58*.92*.85= 0.45356 = 45%
Stovetop kettle efficiency: .98*.35=.343= 34%
Electric kettle more efficient
b)Based on the following information, how does a 1000W microwave compare to the stovetop and electric kettles in terms of water-heating efficiency? Calculate both electricity-to-heat and overall efficiency (assuming electricity from a natural gas fired power plant). Please express your answer as a percentage.
-A 1000W microwave takes 120 seconds to boil 8 oz of water.
-The boiling point of water is 100°C, and room temperature water is 20°C
-The specific heat of water is 4.186 J/gC
c)Electric kettles are quite efficient, but people often use them carelessly and boil more water than they need – while microwaves are typically used to boil the precise amount needed at a time. If the average kettle ends up boiling 2 times as much water as needed, while the microwave boils the exact amount, how does this change efficiencies from parts a and b? Assume that the amount of water boiled does not change how much heat is lost to the kettle itself.
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