Holooly Plus Logo
Holooly Plus Logo

Question 2.6: Heating of an Oven by Heat Transfer Answer the question in E...

Heating of an Oven by Heat Transfer

Answer the question in Example 2-5 if the system is taken as only the air in the oven without the heating element.

The Blue Check Mark means that this solution has been answered and checked by an expert. This guarantees that the final answer is accurate.
Learn more on how we answer questions.

The question in Example 2-5 is to be reconsidered by taking the system to be only the air in the oven.

Analysis This time, the system boundary will include the outer surface of the heating element and will not cut through it, as shown in Fig. 2-25.

Therefore, no electrons will be crossing the system boundary at any point.
Instead, the energy generated in the interior of the heating element will be transferred to the air around it as a result of the temperature difference between the heating element and the air in the oven. Therefore, this is a heat transfer process.

Discussion For both cases, the amount of energy transfer to the air is the same. These two examples show that an energy transfer can be heat or work, depending on how the system is selected.

2.25

Related Answered Questions

A Car Powered by Nuclear Fuel An average car consumes about 5 L of gasoline a day, and the capacity of the fuel tank of a car is about 50 L. Therefore, a car needs to be refueled once every 10 days. Also, the density of gasoline ranges from 0.68 to 0.78 kg/L, and its lower heating value is about

Verified Answer:
A car powered by nuclear energy comes equipped wit...

Wind Energy A site evaluated for a wind farm is observed to have steady winds at a speed of 8.5 m/s (Fig. 2-12). Determine the wind energy (a) per unit mass, (b) for a mass of 10 kg, and (c) for a flow rate of 1154 kg/s for air.

Verified Answer:
A site with a specified wind speed is considered. ...

Burning of a Candle in an Insulated Room A candle is burning in a well-insulated room. Taking the room (the air plus the candle) as the system, determine (a) if there is any heat transfer during this burning process and (b) if there is any change in the internal energy of the system.

Verified Answer:
A candle burning in a well-insulated room is consi...

Heating of a Potato in an Oven A potato initially at room temperature (25°C) is being baked in an oven that is maintained at 200°C, as shown in Fig. 2-23. Is there any heat transfer during this baking process?

Verified Answer:
A potato is being baked in an oven. It is to be de...

Heating of an Oven by Work Transfer A well-insulated electric oven is being heated through its heating element. If the entire oven, including the heating element, is taken to be the system, determine whether this is a heat or work interaction.

Verified Answer:
A well-insulated electric oven is being heated by ...

Power Transmission by the Shaft of a Car Determine the power transmitted through the shaft of a car when the torque applied is 200 N-m and the shaft rotates at a rate of 4000 revolutions per minute (rpm).

Verified Answer:
The torque and the rpm for a car engine are given....

Power Needs of a Car to Climb a Hill a Consider a 1200-kg car cruising steadily on a level road at 90 km/h. Now the car starts climbing a hill that is sloped 30° from the horizontal (Fig. 2-37). If the velocity of the car is to remain constant during climbing, determine the additional power that

Verified Answer:
A car is to climb a hill while maintaining a const...

Power Needs of a Car to Accelerate Determine the power required to accelerate a 900-kg car shown in Fig. 2-38 from rest to a velocity of 80 km/h in 20 s on a level road.

Verified Answer:
The power required to accelerate a car to a specif...

Acceleration of Air by a Fan A fan that consumes 20 W of electric power when operating is claimed to discharge air from a ventilated room at a rate of 1.0 kg/s at a discharge velocity of 8 m/s (Fig. 2-50). Determine if this claim is reasonable.

Verified Answer:
A fan is claimed to increase the velocity of air t...

Annual Lighting Cost of a Classroom The lighting needs of a classroom are met by 30 fluorescent lamps, each consuming 80 W of electricity (Fig. 2-52). The lights in the classroom are kept on for 12 hours a day and 250 days a year. For a unit electricity cost of 7 cents per kWh, determine annual

Verified Answer:
The lighting of a classroom by fluorescent lamps i...