Tag: alternative fuels and energy sources

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Questions Related to alternative fuels and energy sources

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

Hydrogen is not used as a household fuel because:

  1. it is highly combustible gas

  2. its transportation is difficult

  3. Is not easily available

  4. all of these are true
Reveal answer Fill a bubble to check yourself
D Correct answer
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.
Multiple choice evs - i substances, objects and energy renewable resources alternative fuels and energy sources alternative sources of energy

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,

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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.
Multiple choice evs - i substances, objects and energy renewable resources alternative fuels and energy sources alternative sources of energy

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:

  1. halved

  2. unchanged

  3. doubled
  4. increased by factor $\sqrt2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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

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.

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

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

  1. Point of Buoyancy

  2. Centre of Mass

  3. Point of Pressure

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


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

A ball of mass 50 g is thrown upwards. It rises to a maximum height of 100 m. At what height its kinetic energy will be reduced to 70%?

  1. 30 m

  2. 40 m

  3. 60 m

  4. 70 m
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

By work energy theorem,

$U _i+K _i=U _f+K _f$
$0+K _i=mgh+0$
$K _i=(50\times10^{-3})(10)(100)J$
$K _i=50J$ $-(i$)
Now, we have $K _f=\dfrac{70}{100}K _i$
By work energy theorem,
$0+K _i=mgh+\dfrac{70}{100}K _i$
$K _i-\dfrac{70}{100}K _i=(50\times10^{-3})(10)(h)$
$\dfrac{30}{100}K _i=0.5h$
From $(i)$, we have $K _i=50$
$h=2\times\dfrac{30}{100}\times50m$
$h=30m$

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

The total energy of an electron is 3.555 MeV then its kinetic energy is

  1. $3.545 \mathrm { MeV }$
  2. $3.045 \mathrm { MeV }$
  3. $3.5 \mathrm { MeV }$

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

Every substance has energy due to its mass$:$

loss in energy
$\Delta E = \Delta m{c^2}$
$\therefore KE = \left( {m - {m _0}} \right){c^2}$
$ = 3.555 - {m _0}{c^2}$
$ = 3.555 - 0.51$
$ = 3.045MeV$
Hence,
option $(B)$ is correct answer.

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

A steady beam of alpha-particles $(p=2e)$ traveling with constant kinetic energy $20$ $MeV$ carries a current $0.251$ x $10^{-6}$. If the beam is directed perpendicular to a plane surface, how many alpha-particles strike the surface in $3$ secs? 

  1. $2.3$ x $10^{12}$
  2. $2.3$ x $10^{19}$
  3. $2.3$ x $10^{8}$
  4. $2.3$ x $10^{6}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Current is given by I = q / t = (N * q_alpha) / t, where q_alpha = 2e. Given I = 0.251 x 10^-6 A and t = 3 s, total charge Q = I * t = 0.251 x 10^-6 * 3 = 0.753 x 10^-6 C. The charge of an alpha particle is 2e = 2 * 1.6 x 10^-19 = 3.2 x 10^-19 C. The number of particles N = Q / (2e) = 0.753 x 10^-6 / (3.2 x 10^-19) = 2.35 x 10^12 particles.