Tag: charge

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Questions Related to charge

Multiple choice physics static electricity properties of charges charge properties of charge

If the number of electric lines of force emerging out of a closed surface is 1000, then the charge enclosed by the surface is

  1. $8.854 \times {10^{ - 9}}C$
  2. $8.854 \times {10^{ - 4}}C$
  3. $8.854 \times {10^{ - 1}}C$
  4. $8.854\,C$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given that $\phi $, no. of field lines $=1000$

From gauss law,
$\phi =\dfrac { { Q } _{ inc } }{ { \varepsilon  } _{ 0 } } $
$\therefore \quad 1000=\dfrac { { Q } _{ inc } }{ 8.85\times { 10 }^{ -12 } } $
$\Rightarrow \quad { Q } _{ inc }=8.85\times { 10 }^{ -12 }\times 1000$
                   $=8.854\times { 10 }^{ -9 }C$

$\therefore $  Option (A) is the correct answer.

Multiple choice physics static electricity properties of charges charge properties of charge

Two insulated charged spheres of radii $20cm$ and $25cm$ respectively and having equal charge $q$ are connected by a copper wire and then they are separated

  1. Both the spheres will have same charge $q$
  2. The charge on $20cm$ sphere will be greater than on the $25cm$ sphere
  3. The charge on $25cm$ sphere will be greater than on the $20cm$ sphere

  4. Both have same charge density

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

After redistribution, charges on them will be different, but they will acquire common potential i.e.

$k\frac{Q _1}{r _1}=k\frac{Q _2}{r _2}\Rightarrow\frac{Q _1}{Q _2}=\frac{r _1}{r _2}$
As,
$\sigma=\frac{Q}{4\pi r^2}$
$\frac{\sigma _1}{\sigma _2}=\frac{Q _1}{Q _2}\times \frac{r _2^2}{r _1^2}\Rightarrow \frac{\sigma _1}{\sigma _2}=\frac{r _2}{r _1}$
$\sigma \propto \frac{1}{r}$ i.e. surface charge density on smaller sphere will be more.

Multiple choice physics static electricity properties of charges charge properties of charge

There are $4\times { 10 }^{ 23 }$ atoms in a metal sphere. If one electron is removed from $0.1\%$ of atoms, what will be the charge on the sphere?

  1. $-6.4C$
  2. $64C$
  3. $0.64C$
  4. $-64C$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Given, 

$n=4\times 10^{23}\times 0.1$%

$n=4\times 10^{23}\times \dfrac{0.1}{100}=4\times 10^{20}$

$e=1.6\times 10^{-19}C$

The charge is quantised, $q=ne$

$q=4\times 10^{20}\times 1.6\times 10^{-19}=64C$

The electron is negative charge particle.

So,$q=-64C$

The correct option is D.
Multiple choice physics static electricity properties of charges charge properties of charge

The density of field lines surrounding any given object reveal information about the

  1. the nature of charge on the source charge.

  2. the quantity of charge on the source charge.

  3. both A and B

  4. it reveals no information
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The density of field lines shows the strength of field, and hence reveal the information about the magnitude of charge that is quantity of charge on the source.

Multiple choice physics static electricity properties of charges charge properties of charge

The energy acquired by a charge of $8 \times 10 ^ { - 19 } { C }$ when passed through a potential difference of $200\ volt$

  1. $500 \mathrm { eV }$
  2. $1000 \mathrm { eV }$
  3. $1500 \mathrm { eV }$
  4. $2000 \mathrm { eV }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\begin{array}{l} U=qV \ =8\times { 10^{ -19 } }\times 200J \ =\dfrac { { 8\times { { 10 }^{ -19 } }\times 200 } }{ { 1.6\times { { 10 }^{ -19 } } } } eV \ =1000ev \ Hence,\, the\, option\, B\, is\, the\, correct\, answer. \end{array}$

Multiple choice physics static electricity properties of charges charge properties of charge

Two charges of equal magnitude and at a distance'r' exert a force $F$ on each other. If the charges are halved and distance between them is doubled, then the new force acting on each charge is

  1. $F / 8$
  2. $F / 4$
  3. $4 F$
  4. $F / 16$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Original force$,$

$F = k\dfrac{{q\,q}}{{{r^2}}}$
New force$,$
$F = k\dfrac{{\dfrac{q}{2}\,\dfrac{q}{2}}}{{{{\left( {2r} \right)}^2}}} = \dfrac{1}{{16}}F = \dfrac{F}{{16}}$
Hence,
option $(D)$ is correct answer. 

Multiple choice physics static electricity properties of charges charge properties of charge

Mark the correct options : 

  1. The total charge of the universe is constant.

  2. The total positive charge of the universe is constant.

  3. The total negative charge of the universe is constant.

  4. The total number of charged particles in the universe is constant.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The law of conservation of charges states that electric charge can neither be created nor destroyed.
Hence the net quantity of electric charge of the universe is always conserved. 

Multiple choice physics static electricity properties of charges charge properties of charge

$\displaystyle \frac {4}{25}$ Coulomb of charge contains .......... electrons

  1. $10^{15}$
  2. $10^{18}$
  3. $10^{20}$

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

The formula for quantization of charge is given as q=ne.
where q is the amount of charge in Columbu's, n is the number of charges and e is the charge on the electron.
In this case, q=4/25 C
So, e = $1.6\times { 10 }^{ -19 }C$.
n can be calculated as n=q/e = $\frac { 4 }{ 25 } \times [\dfrac { 1 }{ 1.6\times { 10 }^{ -19 }C } ]\quad =\quad { 10 }^{ 18 }$ which is the number of electrons.
Hence, 4/25 Coulomb of charge contains ${ 10 }^{ 18 }$ electrons.