In: Mechanical Engineering
Indicate whether the following statements are true or false. Explain.
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1) True. Energy transferred due to Temperature difference is Heat. The rate of energy transfer is Power.
2)True. Heat and work are forms of energies that exchange between the system and surroundings.
3)False. At an elevation, the object is at rest initially. It means the body has only potential energy. When it hits the ground and comes to rest at 0 elevation, it will not have both kinetic energy and potential energy. It means, the kinetic energy is dissipated in terms of lossess like drag and friction, but Kinetic Energy is not converted to potential energy.
4) True. Energy is stored in form of Kinetic, Potential and Internal Energies.
5) True. In a cycle, since the intial and final states are same, the i ternal energy is same for initial and final positions. According to first law (dQ = W + dU), since dU is 0, heat is equal to work for a cycle.
6) False. Work is said to be done only when there is a change of volume. The electric resistor inside a tank of gas will not cause a change of volume. So it is not work done but merely, heat transfer.
7) True. Internal energy is a measure of temperature. Since temperature is a very important property to define the state of a system, internal energy is significant.
8) True. The effeciency of a heat engine is between 0 and 1. The COP of heat pump is given by 1/(effeciency of heat engine). So the COP of heat pump is always greater than 1. COPref = COPhp - 1. So, The COP of refregerator can take all the values from 0 to infinity (theoretically)
9)False. Heat is referred to the energy that transfers. So, it is not correct to say a system contains heat.
10)True. The definition of Adiabatic process itself says that the heat transfer is 0