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Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics nuclei gamma decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

The total energy of an electron in the ground state of hydrogen atom is $-13.6\space eV$. The potential energy of an electron in the ground state of $Li^{2+}$ ion will be

  1. $122.4\space eV$

  2. $-122.4\space eV$

  3. $244.8\space eV$

  4. $-244.8\space eV$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Therefore, for ${ Li }^{ 2+ }$ ion, Total energy is $- 13.6\times 9 = 122.4\ eV$
But, $-K.E= T.E= \dfrac { P.E }{ 2 } $
Therefore, $P.E$ is $-244.8\ eV$

Multiple choice physics nuclei gamma decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

The ground state energy of Hydrogen atom is $–13.6eV$. The potential energy of the electron in this state is:

  1. $0eV$

  2. $-27.2eV$

  3. $1eV$

  4. $2eV$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The ground state energy of hydrogen atom $=13.6eV$

Potential energy $=2$ energy of electron
                             $=2(-13.6\ eV)$
                             $=-27.2\ eV$

Multiple choice physics nuclei gamma decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

In which of the following systems will the radius of the first orbit (n = 1) be minimum ?

  1. hydrogen atom

  2. deuterium atom

  3. singly ionized helium

  4. doubly ionized lithium.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Radius of the first orbit of an atom  $R _1 = \dfrac{0.529}{Z}$  $A^o$
$\implies \ R _1 \propto\dfrac{1}{Z}$
where $Z$ is the atomic number of Hydrogen-like atom.
Since $Z$ is maximum for doubly ionized lithium, thus radius of first orbit is minimum in doubly ionized lithium.

Multiple choice physics effects of electric current joule's law of heating thermal effect of electric current heating effect of electric current

A/c to Joules's law, if the potential difference across a conductor having a material of specific resistance (P) remains constant, then the heat produced in the conductor is directly proportional to

  1. $\displaystyle P$

  2. $\displaystyle { P }^{ 2 }$

  3. $\displaystyle \frac { 1 }{ \sqrt { P } } $

  4. $\displaystyle \frac { 1 }{ P } $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let the specific resistance of the material be  $P$.

$\therefore$  Resistance of the conductor        $R = \dfrac{P L}{A}$
According to Joule's heating effect,  heat produced     $H = \dfrac{V^2t}{R}$

$\therefore$   $H = \dfrac{V^2 t}{PL/A}  = \dfrac{V^2A t}{L}\dfrac{1}{P}$              $\implies H\propto \dfrac{1}{P}$

Multiple choice physics effects of electric current joule's law of heating thermal effect of electric current heating effect of electric current

Joule's heating effect is

  1. Reversible

  2. Irreversible

  3. Both

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

Joule heating effect is irreversible that means if the direction of current in a resistor is reversed, the cooling of resistor does not occur whereas heating of the resistor takes place.

Heat produced via Joule's heating effect    $H = i^2Rt$ 

Multiple choice physics effects of electric current joule's law of heating thermal effect of electric current heating effect of electric current

J (Joule's mechanical equivalent of heat) is equal to

  1. 2400J

  2. $\displaystyle 4.18J{ cal }^{ -1 }$

  3. $\displaystyle 2.2J{ cal }^{ -1 }$

  4. 1000J
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
According to Joule's law, mechanical equivalent of heat    $J = \dfrac{W}{Q}$
Mathematically    $J = 4.18$  $Jcal^{-1}$ if work done and heat produced is measured in joules and calories respectively.
Multiple choice physics effects of electric current joule's law of heating thermal effect of electric current heating effect of electric current

From below which one is the equation for Joule's law of heating effect of electricity?

  1. $H=I^2Rt$

  2. $H=IR^2t$

  3. $H=IRt^2$

  4. $H=\dfrac{It^2}{R}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to Joule's law of heating,  heat produced in a resistor     $H = I^2Rt$

where $I$ and $t$ are the current flowing through the resistor and time of current flowing respectively.