Tag: option b: engineering physics

Quizzes (17) Questions (184)

Questions Related to option b: engineering physics

Multiple choice physics option b: engineering physics conversion of heat into work: heat engine and it's efficiency engines and cycles refrigerators and heat pumps

A heat engine is supplied with 250 kJ/s of heat at a constant fixed temperature of $227^0C$; the heat is rejected at $27^0C$, the cycle is reversible, then what amount of heat is rejected?

  1. 24kJ/s

  2. 223kJ/s

  3. 150kJ/s

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The temperature in kelvin scales are $T _1=273+27=300K,T _2=273+237=500K$

$T _1$is temperature of sink And$T _2$ is temperature of source hence by efficiency we get

$\eta=1-\dfrac{T _1}{T _2}=1-\dfrac{Q _1}{Q _2}$


$Q _1=\dfrac{T _1}{T _2}*Q _2=\dfrac{300}{500}*250=150kW$
Multiple choice physics option b: engineering physics conversion of heat into work: heat engine and it's efficiency engines and cycles refrigerators and heat pumps

An engine working on Carnot cycle rejects 40% of absorbed heat from the source, while the sink temperature is maintained at $27^0C$, then what is the source temperature (in $^0C$)?

  1. 477

  2. 346

  3. 564

  4. none of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$\eta =\dfrac { 60 }{ 100 } $

${ T } _{ 2 }={ 27 }^{ o }C$
${ T } _{ 2 }={ 300 }^{ o }K$
${ T } _{ 1 }=?$

$\eta =\dfrac { { T } _{ 1 }-{ T } _{ 2 } }{ { T } _{ 1 } } $

Here, ${ T } _{ 1 }=Source\quad temperature$
${ T } _{ 2 }=sink\quad temperature$
$\eta =Efficiency$
$\eta =100-rejecion$

$\therefore \dfrac { 60 }{ 100 } =\dfrac { { T } _{ 1 }-{ T } _{ 2 } }{ { T } _{ 1 } } $

$\therefore 0.6=\dfrac { { T } _{ 1 }-300 }{ { T } _{ 1 } } $

$\therefore { T } _{ 1 }\left( 1-0.6 \right) =300$

${ T } _{ 1 }=\dfrac { 300 }{ 0.4 } =\dfrac { 3000 }{ 4 } ={ 750 }^{ o }K$

$\therefore { T } _{ 1 }={ \left( 750-273 \right)  }^{ o }C$
$\therefore { T } _{ 1 }={ 477 }^{ o }C$
Multiple choice physics option b: engineering physics conversion of heat into work: heat engine and it's efficiency engines and cycles refrigerators and heat pumps

One reversible heat engine operates between 1600 K and $T _2$ K, and another reversible heat engine operates between $T _2$ K and 400 K. If both the engines have the same heat input and output, then the temperature $T _2$ must be equal to:

  1. 600

  2. 800

  3. 650

  4. 675
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

${ T } _{ 1 }=1600K$


${ T } _{ 2 }={ T } _{ 2 }K$


${ T } _{ 1 }^{ 1 }={ T } _{ 2 }K$

${ T } _{ 2 }^{ 1 }=400K$

Same input and same output.Then the efficiency is same.
$\eta =\dfrac { { T } _{ 1 }-{ T } _{ 2 } }{ { T } _{ 1 } } $

$\therefore \dfrac { 1600-{ T } _{ 2 } }{ 1600 } =\dfrac { { T } _{ 2 }-400 }{ { T } _{ 2 } } $

$=1600{ T } _{ 2 }-{ T } _{ 2 }^{ 2 }=1600{ T } _{ 2 }-640000$

$\therefore { T } _{ 2 }^{ 2 }=640000$
$\therefore { T } _{ 2 }=800K$

Multiple choice physics option b: engineering physics conversion of heat into work: heat engine and it's efficiency engines and cycles refrigerators and heat pumps

The freezer in a refrigerator is located at the top section so that;

  1. The entire chamber of the refrigerator is cooled quickly due to convection

  2. The motor is not heated

  3. The heat gained from the environment is high

  4. The heat gained from the environment is low
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The freezer in a refrigerator is located at the top section so that the entire chamber of the refrigerator is cooled quickly due to convection.  
The correct option is A.

Multiple choice physics option b: engineering physics conversion of heat into work: heat engine and it's efficiency engines and cycles refrigerators and heat pumps

If the door of a refrigerator is kept open, the room in which the refrigerator is kept 

  1. gets cooled

  2. gets heated

  3. neither gets cooled nor gets heated

  4. gets cooled or heated depending on the initial temperature of the room
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A refrigerator works by absorbing heat from its interior and releasing it into the surrounding room through the condenser coils at the back. When the door is kept open, the refrigerator draws in more warm room air and continuously runs, ultimately expelling more heat into the room than it removes, causing the room temperature to rise.

Multiple choice rotational equilibrium option b: engineering physics motion of system of particles and rigid bodies equilibrium physics

Consider the following statements:
(a)  Change in momentum is impulse.
(b)  A body is momentarily at rest when it reverse the direction.
(c)  For stable equilibrium force has to be zero and potential energy should be minimum.
(d)  Force required to accelerate a mass in two perpendicular directions is never same.
Which of the above statements are correct?

  1. (b) and (c)

  2. (a) and (b)

  3. (a), (b) and (d)

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All of the above
Impulse = Force$\times$time = $m\Delta{v}$ = Momentum
A body will be at rest for a moment when it changes direction.
When a body is in equilibrium it always has minimum potential energy and no force is acting upon it.
Force is a vector quantity and hence its direction will result in different force quantity.

Multiple choice rotational equilibrium option b: engineering physics motion of system of particles and rigid bodies equilibrium physics

State whether given statement is True or False.

When any object is in equilibrium, the sum of all the forces acting on it is zero.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When an object is not in equilibrium, net force acting on the body is not zero.
Therefore when some force acts on the object, it is in accelerated motion because, $F= ma$

Multiple choice rotational equilibrium option b: engineering physics motion of system of particles and rigid bodies equilibrium physics

When a body remains in the state of rest conditions under the influence of applied forces, the body is in 

  1. Dynamic equilibrium

  2. Static equilibrium

  3. Both

  4. None
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The equilibrium is of two types
(1) Static equilibrium
(2) Dynamic equilibrium
When a body remains in the state of rest under the influence of the applied forces, the body is in static equilibrium.

Multiple choice rotational equilibrium option b: engineering physics motion of system of particles and rigid bodies equilibrium physics

A body is in translatory equilibrium if:

  1. Resultant force on it is zero

  2. It is at rest

  3. It is in uniform motion

  4. All options are correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A body is said to be in translatory equilibrium when net external force acting on it is zero.

Also if no external force is acting on the body, then the body must be at rest or moving with constant velocity i.e moves in uniform motion. Hence option D is correct.