Physics

Power, Energy, and Efficiency

463 Questions

Power, energy, and efficiency are fundamental physics concepts that quantify work and the rate of doing work. Questions cover electrical energy consumption in kilowatt hours, the efficiency of thermodynamic cycles like the Brayton cycle, and mechanical power lifting loads. This topic is essential for general science and engineering exam preparation.

Electrical energy consumptionBrayton cycle efficiencyPower calculation formulasCommercial electricity unitsHydraulic lift mechanics

Power, Energy, and Efficiency Questions

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

One milligram of matter is converted into energy. The energy released will be

  1. $9\times 10^{6} J$
  2. $9\times 10^{8}J$
  3. $9\times 10^{10}J$
  4. $9\times 10^{12}J$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Here, $m = 1\ mg = 1\times 10^{-3} g $

             $= 1\times 10^{-6}kg$
According to Einstein mass-energy equivalence
                $E = mc^{2}$
where $c$ is the speed of light in vacuum
$\therefore E = (1\times 10^{-6} kg)(3\times 10^{8}ms^{-1})^{2}$
$ = 9\times 10^{10}J$.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The conversion of 1 u of mass results in ________ eV of energy.

  1. $9.315 \times 10^6$
  2. $391.5 \times 10^6$
  3. $931.5 \times 10^6$
  4. $93.15 \times 10^6$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Einstein's mass-energy equivalence principle, 1 atomic mass unit (u) is equivalent to approximately 931.5 MeV of energy. Since 1 MeV equals 10^6 eV, 931.5 MeV equals 931.5 * 10^6 eV.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

One milligram of matter convert into energy will give

  1. $90 joule$
  2. $9\times { 10 }^{ 3} joule$
  3. $9\times { 10 }^{ 5} joule$
  4. $9\times { 10 }^{ 10} joule$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$E={ mc }^{ 2 }={ 10 }^{ -3 }\times{ 10 }^{ -3 } \left( 3\times { 10 }^{ 8 } \right) ^{ 2 }=9\times { 10 }^{ 10 }J$

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

1mg of matter convert into energy will give

  1. $90$ joule
  2. $9\times { 10 }^{ 3 }$ joule
  3. $9\times { 10 }^{ 5 }$ joule
  4. $9\times { 10 }^{ 10 }$ joule
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$E=m{ c }^{ 2 }=10^{ -3 }\times { 10 }^{ -3 }\times { \left( 3\times { 10 }^{ 8 } \right)  }^{ 2 }= 9\times { 10 }^{ 10 }J$

Multiple choice chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

Energy spent in kilowatt-hour $=\cfrac {volt \times...........\times......}{1000}$.

  1. ampere, hour

  2. ohm,min

  3. ampere,min

  4. joule,hour
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Energy = Work done $(in\ Watt) =  Power\times time = Voltage \times current \times time$


$Work\ done\ (in\ kilowatt) = \dfrac{(Voltage\times current\times time)}{ 1000}$

$Or\ work\ done\ (in\ kilowatt) = \dfrac{(Volt\times ampere\times hour)}{ 1000}$

Multiple choice economics environment and sustainable development need for sustainable development environmental economics sustainable development

At present, nearly ____________$\%$ of the energy consumed is obtained from Non-Commercial Traditional Sources.

  1. $45$
  2. $51$
  3. $23$
  4. $10$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Statistical data on energy consumption in India historically indicates that traditional sources account for approximately 23 percent of total energy consumption.

Multiple choice maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

A generator consumes 2.875 litres of diesel per hour.The quantity of diesel required to run the generator for 24 hours is ______ .

  1. $45$ litres
  2. $55$ litres
  3. $72$ litres
  4. $69$ litres
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\Rightarrow$  Diesel consumes by generator in $1\,hour$ = $2.875\,liters.$

$\Rightarrow$  Diesel consumes by generator in $24\,hours=24\times 2.875\,liters$
$\therefore$  Diesel consumes by generator in $24\,hours=69\,liters$.

Multiple choice maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

A machine produces $2800$ screws in a day. Which of the following is the best estimate of the number of screws produced in 2 days?

  1. $3500$
  2. $5000$
  3. $3000$
  4. $2900$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A machine produces $2800$ screws in a day.

Hence it will produce $2800\times2$ screws in $2$ days
$=5600$ screws in $2$ days
The best estimate of the number of screws produced in $2$ days is $5000$
Hence Option B