Tag: physics

Questions Related to physics

The wire having a black plastic covering is a

physics electric current and circuit domestic electric circuits and safety precautions domestic and commercial circuit electric power

  1. live wire

  2. neutral wire

  3. earth wire

  4. none of these

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Correct Option: B
Explanation:

During wiring in our houses , we use the traditional concept of using red color wire as live , black as neutral and green for earth.These color codes are used to distinguish between live, neutral and earth. which is a standard way of coding of colors for electric connections.

According to new convention, earth wire is coded by

physics electric current and circuit domestic electric circuits and safety precautions domestic and commercial circuit electric power

  1. Green colour

  2. Black colour

  3. Red colour

  4. All

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Correct Option: A
Explanation:

According to new convention, live wire of codded by brown colour, neutral wire is coded by light blue colour whereas earth wire is coded by green and yellow colour.

All domestic electrical circuits are connected

physics electric current and circuit domestic electric circuits and safety precautions domestic and commercial circuit electric power

  1. In series

  2. In parallel

  3. Both

  4. None of these

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Correct Option: B
Explanation:

Electric circuits are connected parallely so that if there is problem in any circuit the other circuit does not get affected.

Neutral wire is usually insulated with

physics electric current and circuit domestic electric circuits and safety precautions domestic and commercial circuit electric power

  1. Red colour

  2. Brown colour

  3. Black colour

  4. Green colour

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Correct Option: C
Explanation:

Live wire has an insulation of red or brown colour. Neutral wire with an insulation of black or blue colour.

Which is not a non-renewable source of energy?

physics world energy needs coal petroleum non-renewable sources of energy

  1. coal

  2. petrol

  3. wind

  4. petroleum gas

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Correct Option: C
Explanation:

Coal, petroleum gas and petrol are fossil fuels. Fossil fuels are good for one time use. But wind is a renewable source of energy.

Which of the following relations is correct?

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $E = mc$

  2. $E = mc^2$

  3. $E = 2mc^2$

  4. $E = mc^2/4$

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Correct Option: B
Explanation:

According to Einstein, energy and mass are related by the relation.
$E = mc^2$
where c is the speed of light in vacuum.

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

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $9\times 10^{6} J$

  2. $9\times 10^{8}J$

  3. $9\times 10^{10}J$

  4. $9\times 10^{12}J$

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Correct Option: C
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$.

The relation between the volume $V$ and the mass $M$ of a nucleus is:

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $V\propto M^{3}$

  2. $V\propto M^{1/3}$

  3. $V\propto M$

  4. $V\propto 1/M$

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Correct Option: C
Explanation:

Since the density of nucleus is fixed.

$D=\cfrac { M }{ V } \ \Rightarrow M=DV\ M\propto V$

A student wrote the relation for one unified atomic mass unit (u) as $1u=931.5MeV$. What is the correct relation?

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $1 u\times c=931.5 MeV$

  2. $1 u\times c^2=931.5 MeV$

  3. $\dfrac{1u}{c^2}=931.5 MeV$

  4. $(1u)^2\times c=931.5Me V$

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Correct Option: B
Explanation:

$1u=931.5 MeV$
we know $1u=1.66\times 10^{-21}kv$
$931.5 MeV=931.5\times 10^6\times 1.6\times 10^{-19}J=1.49\times 10^{-10}$
$E=(1u)(c^2)=(1.66\times 10^{-27})(3\times 10^8)^2J=1.494\times 10^{-10}J$
so $(1u)(c)^2=931.5MeV$

A nucleus of mass number $A$ originally at rest emits $\alpha$- particle with speed $v$. The recoil speed of daughter nucleus is:

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $\cfrac{4v}{A-4}$

  2. $\cfrac{4v}{A+4}$

  3. $\cfrac{v}{A-4}$

  4. $\cfrac{v}{A+4}$

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Correct Option: A