Tag: substances, objects and energy

Questions Related to substances, objects and energy

Forms of energy of sun are:

evs - i substances, objects and energy renewable resources alternative fuels and energy sources alternative sources of energy conservation of fossil fuels

  1. wind energy

  2. bioenergy

  3. light and heat

  4. all of these

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Correct Option: C
Explanation:

The forms of energy from the sun are heat and light.

Which of the following is not a gaseous fuel?

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

  1. CNG

  2. Coal gas and water gas

  3. Gobar gas and acetylene

  4. Liquid hydrogen.

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Correct Option: D
Explanation:
Solid fuels include peat, coal, wood, biomass.
Liquid fuels include petroleum, alcohol.
Gaseous fuel includes natural gas.
Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen.

Which one of the following is not a characteristic of a good fuel?

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

  1. No emission of smoke or harmful gases

  2. High ignition temperature

  3. High calorific value

  4. Not much ash(residue) after burning

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Correct Option: B
Explanation:
Characteristics of a good fuel are as follows:
1. Cheap and easily available.
2. Easy to store and transport.
3. Low ash content.
4. Should not produce any harmful substances.
5. High calorific value.
6. Moderate ignition temperature. 

Which fuel has the highest calorific value?

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

  1. Hydrogen gas

  2. Methane

  3. Wood

  4. Petrol

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Correct Option: A
Explanation:
Fuels with calorific values:
1. Hydrogen: $150 \ KJ/g$
2. Methane: $55\  KJ/g$
3. LPG: $50 \ KJ/g$
4. Kerosene oil:$ 48 \ KJ/g$
5. Charcoal: $33\  KJ/g$
6. Wood: $17\  KJ/g$

Hydrogen is not used as a household fuel because:

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

  1. it is highly combustible gas

  2. its transportation is difficult

  3. Is not easily available

  4. all of these are true

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Correct Option: D
Explanation:
Though hydrogen has the highest calorific value, it is not used as a household fuel because:
1. It is not easily available and this makes it costly too.
2. It is highly combustible.
3. Transportation is difficult.

An energy efficient device for producing light is:

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

  1. CFL

  2. CNG

  3. LPG

  4. MCB

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Correct Option: A
Explanation:

Compact fluorescent light bulbs are used in place of incandescent bulb because they use about 1/7 of the power used by the incandescent bulb. Hence, they are highly efficient in saving electricity.

An electron and a proton are moving under the influence of mutual forces. In calculating the change in the kinetic energy of the system during motion, one ignores the magnetic force of one on another. This is because,

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

  1. the two magnetic forces are equal and opposite, so they produce no net effect

  2. the magnetic forces do no work on each particle.

  3. the magnetic forces do equal and opposite (but non-zero) work on each particle

  4. the magenetic forces are necessarily negligible

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Correct Option: B
Explanation:
The electric and magnetic forces are defined via the Lorentz force on a charged particle

$F =q(E +v ×B )$
The magnetic force comes from the second term which defines it to be perpendicular to the velocity and therefore displacement $dr$ so it doesn't do any work.

A sealed container with negligible coefficient of volumetric expansion contains helium (a mono-atomic gas). When it is heated from 300 K to 600 K, the average KE of helium atoms is:

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

  1. halved

  2. unchanged

  3. doubled

  4. increased by factor $\sqrt2$

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Correct Option: C
Explanation:

$the\quad avarage\quad KE\quad of\quad n\quad moles\quad of\quad gas\quad at\quad temp\quad T\quad is\quad \dfrac { 3 }{ 2 } nRT\ when\quad temp\quad is\quad doubled\quad \dfrac { 3 }{ 2 } nR(2T)=2\times \dfrac { 3 }{ 2 } nRT\ so\quad KE\quad doubles$

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

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

  1. 1

  2. 2

  3. 5

  4. 4

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Correct Option: C

A point in the object where entire mass of an object is said to be concentrated is:

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

  1. Point of Buoyancy

  2. Centre of Mass

  3. Point of Pressure

  4. None of these

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Correct Option: B
Explanation:

A point where entire mass of the body is assumed to be concentrated is called center of mass. This point may or may be inside body or outside.