Lecture 2 / ENERGY

Question 1

can exist as thermal, mechanical, kinetic, potential, electric, magnetic, chemical and nuclear. Their sum constitutes the total energy E of the system. e = u + ke + pe = u + V²/2 + gz (kJ/kg)

Answer 1

total energy

Question 2

a system possesses as a whole with respect to some outside reference frame, such as kinetic and potential energies.

Answer 2

macroscopic forms of energy

Question 3

related to the molecular structure of a system and the degree of the molecular activity, independent of the outside reference frames.

Answer 3

microscopic forms of energy

Question 4

The sum of all the microscopic forms of energy, denoted by U.

Answer 4

internal energy

Question 5

is the energy that a system possesses as a result of its motion relative to some reference frame. When all parts of a system move at the same velocity,

Answer 5

kinetic energy

Question 6

is the energy that a system possesses as a result of its elevation in a gravitational field.

Answer 6

potential energy

Question 7

____________ whose velocity and elevation of the **centre of gravity remain constant **during a process are often referred to as _____________

Answer 7

closed systems , Stationary systems

Question 8

The amount of mass flowing through a cross section per unit time. ṁ = ρV̇

Answer 8

mass flow rate ṁ

Question 9

The flow of thermal energy from higher temperature to lower temperature via conduction, convection and radiation.

Answer 9

heat transfer

Question 10

is equal to force multiplied by displacement.

Answer 10

work

Question 11

highest quality of energy, for example, can always be converted to an equal amount of thermal energy ( also called heat )

Answer 11

ELECTRICITY

Question 12

can exist in numerous forms such as thermal, mechanical, kinetic, potential, electric, magnetic, chemical, and nuclear, and their sum constitutes the total energy E of a system

Answer 12

ENERGY

Question 12

typically involve fluid flow for long periods of time, and it is convenient to express the energy flow associated with a fluid stream in the rate form

Answer 12

CONTROL VOLUMES

Question 13

the form of energy that can be converted to mechanical work completely and directly by an ideal mechanical device such as an ideal turbine

Answer 13

MECHANICAL ENERGY

Question 14

energies are the familiar forms of mechanical energy.

Answer 14

KINETIC AND POTENTIAL

Question 15

Is defined as the form of energy that is transferred between two systems ( or a system and its surroundings ) by virtue of temperature difference.

Answer 15

Heat

Question 16

A process during which there is** no heat transfer** is called an ____________

Answer 16

Adiabatic process

Question 17

Is a energy interaction between a system and its surroundings

Answer 17

Work

Question 18

conservation of the quality of energy, not the quantity

Answer 18

Energy Conservation

Question 19

The magnetic, electric, and surface tension effects are significant in some specialized cases only and are usually ignored

Answer 19

total energy of a system

Question 20

Motion of a particle system

Answer 20

Sensible energy

Question 21

Phase change

Answer 21

Latent

Question 22

__________can cross the boundary of a
closed system in two distinct forms:_____________

Answer 22

Energy ; heat and work

Question 23

is energy in transition. It is
recognized only as it crosses the
boundary of a system

Answer 23

heat

Question 24

have inexact differentials designated
by the symbol δ. differential amount of heat or work
is represented by δQ or δW, respectively, instead
of dQ or dW

Answer 24

Path functions

Question 25

The net change (increase or decrease) in the total energy of the system during a process is equal to the difference between the total energy entering and the total energy leaving the system during that process

Answer 25

ENERGY BALANCE

Question 26

An energy interaction that is
not caused by a temperature difference between
a system and its surroundings is work

Answer 26

Work Transfer, W

Question 27

the system serves as an additional mechanism of
energy transfer. When mass enters a system,
the energy of the system increases because
mass carries energy with it

Answer 27

Mass flow

Question 28

Thermodynamics provides no
information about the absolute
value of the total energy. It deals
only with the __________________, which is what matters in
engineering problems

Answer 28

change of the total
energy