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 physics energy and its forms idea of energy introduction to work and energy work and energy

The number of joules that is equal in value to 1 kWh is.

  1. $3.6\times 10^8$
  2. $0.36\times 10^4$
  3. $3.6\times 10^5$
  4. $3.6\times 10^6$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

1 kWh is equal to 3.6 $\times$ 10$^{6}$

1 Watt-sec  is a Joule a watt expended for a second.

Because there’s 3600 seconds in an hour,

then 3600 Ws = 1 Wh = 3600 Joules = 3.6 kJ

so 1000 Wh = 1 kWh = 1000 $\times$ 3.6 kJ = 3.6 MJ = 3.6 $\times$ 10$^{6}$

Multiple choice physics energy and its forms idea of energy introduction to work and energy work and energy

One kilowatt-hour is equivalent to ______  joules.

  1. $\displaystyle 3.6\times 10^{6}$
  2. $\displaystyle 6\times 10^{6}$
  3. $\displaystyle 3\times 10^{6}$
  4. $\displaystyle 1.8\times 10^{6}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

One kilowatt-hour is the energy consumed by a 1 kW device in 1 hour. Since 1 kW = 1000 J/s and 1 hour = 3600 s, 1 kWh = 1000 * 3600 = 3.6 * 10^6 Joules.

Multiple choice physics energy and its forms idea of energy introduction to work and energy work and energy

The number of joules contained in 1kWh is_____

  1. $36 \times 10^2$
  2. $36 \times 10^3$
  3. $36 \times 10^4$
  4. $3.6 \times 10^6$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The kilowatt hour is a unit of energy equal to 3.6 megajoules. If the energy is being transmitted or used at a constant rate over a period of time, the total energy in kilowatt hours is the power in kilowatts multiplied by the time in hours.

Let energy is used as 1J/s. For an hour or 3600 sec. Then total energy used is 3600J. And kWh means 1000$\times$3600.
Which gives $3.6\times10^6$.

Multiple choice physics the essence of change forms of energy and energy conservation energy for everything forms of energy

The energy required to raise a given volume of water from a well can be

  1. Mega watts

  2. Mega newton

  3. Mega joules

  4. Kilo watts
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

unit of energy is joule.

so energy required for raising water from the well is also in joule or kilo joule or mega joule.
watt is unit of energy per unit time and  newton is unit of force.
so best option is option C.
Also 1 Mega joule $=10\times10^6$ joule.

Multiple choice physics turning effects of forces centre of gravity forces - vectors and moments acceleration due to gravity

A body of mass 2 $ \mathrm{kg}  $ is thrown up vertically with $ \mathrm{K.E.}  $ of 490 Joules. If the acceleration due to gravity is 9.8 $ \mathrm{m} / \mathrm{s}^{2}  $ , then the height at which the K.E. of the body becomes half its originalvalue is given by

  1. $50m$
  2. $12.5m$
  3. $25m$
  4. $10m$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Initial K.E. = 490 J. At height h, K.E. = 245 J. By conservation of energy, initial K.E. = final K.E. + potential energy at height h. 490 = 245 + mgh. 245 = 2 * 9.8 * h. h = 245 / 19.6 = 12.5 m.

Multiple choice biology modern agriculture modern equipments in agriculture soil quality methods of crop production

Agricultural tractors generally have a horsepower (HP) of 

  1. 20-50

  2. 50-70

  3. 10-15

  4. 20-25
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Tractors are generally categorised as based on the size, weight and horsepower. It provides high torque and slow speed and thus is very useful in agricultural fields. In India, four wheel tractors for agricultural operations are fitted with 25-80 hp. Walking type tractors are fitted with 8-12 hp engines
Clutch. Thus , the correct answer is option A.
Multiple choice biology modern agriculture modern equipments in agriculture soil quality methods of crop production

The working efficiency per day of deshi plough is

  1. 0.3 ha

  2. 0.4 ha

  3. 0.6 ha

  4. 0.8 ha
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Plough is a tool which is used by the farmers for cultivation of the soil, planting for the sowing of seeds and turning over the soil and cut furrows. The tool is pulled by oxen or tractors through the ground in order to prepare furrows on the land. 

So the correct option is '0.4 ha'.

Multiple choice evs - i substances, objects and energy renewable resources alternative fuels and energy sources alternative sources of energy

If a man speed up 1m/s his KE increases by 44% His original speed in m/s is 

  1. 1

  2. 2

  3. 5

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

Let initial KE be K = 1/2mv^2. New KE is 1.44K = 1/2m(v+1)^2. Taking the ratio: 1.44 = (v+1)^2 / v^2. Taking the square root: 1.2 = (v+1)/v. Thus, 1.2v = v + 1, so 0.2v = 1, which means v = 5 m/s.