Tag: physics

Questions Related to physics

The product of potential difference and charge is measured in 

physics static electricity properties of charges charge properties of charge

  1. colulomb

  2. volt

  3. juole

  4. watt

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Correct Option: A

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

physics static electricity properties of charges charge properties of charge

  1. $500 \mathrm { eV }$

  2. $1000 \mathrm { eV }$

  3. $1500 \mathrm { eV }$

  4. $2000 \mathrm { eV }$

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Correct Option: B
Explanation:

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

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

physics static electricity properties of charges charge properties of charge

  1. $F / 8$

  2. $F / 4$

  3. $4 F$

  4. $F / 16$

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Correct Option: D
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. 

Mark the correct options : 

physics static electricity properties of charges charge properties of charge

  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.

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Correct Option: A
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. 

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

physics static electricity properties of charges charge properties of charge

  1. $10^{15}$

  2. $10^{18}$

  3. $10^{20}$

  4. None of these

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Correct Option: B
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.

The conservation of electric charge implies that

physics static electricity properties of charges charge properties of charge

  1. charge cannot be created

  2. charge cannot be destroyed

  3. the number of charged particles in the universe is constant

  4. simultaneous creation of equal and opposite charges is permissible

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Correct Option: A,B,C
Explanation:

A, B and C are correct. 

A substance is neutral due to the presence of equal magnitude of positive and negative charge on it.
Although D is possible in radioactivity and its reactions, it is not related to the statement of the question

The number of electrons for one coulomb of charge are:

physics static electricity properties of charges charge properties of charge

  1. $\displaystyle 6.25\times { 10 }^{ 23 }$

  2. $\displaystyle 6.25\times { 10 }^{ 21 }$

  3. $\displaystyle 6.25\times { 10 }^{ 18 }$

  4. $\displaystyle 6.25\times { 10 }^{ 19 }$

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Correct Option: C
Explanation:

1 electron carries a charge of $1.6 \times 10^{-19}$ coulomb 

So, No.of electron in one coulomb
$\dfrac{1}{1.6 \times 10^{-19}} = \dfrac{10^{19}}{1.6} = 6.25 \times 10^{18}$

How many electrons make up a charge of $\displaystyle 20\mu C$ ?

physics static electricity properties of charges charge properties of charge

  1. $\displaystyle 1.25\times { 10 }^{ 14 }$

  2. $\displaystyle 2.23\times { 10 }^{ 14 }$

  3. $\displaystyle 3.25\times { 10 }^{ 14 }$

  4. $\displaystyle 5.25\times { 10 }^{ 14 }$

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Correct Option: A
Explanation:

Charge on an electron $= 1.6 \times 10^{-19}$coulomb

no of electrons required $ = \dfrac{20 \times 10^{-6}}{1.6 \times 10^{-19}} = 1.25 \times 10^{14}$

When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will :

physics static electricity properties of charges charge properties of charge

  1. decrease

  2. increase

  3. remain constant

  4. none

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Correct Option: B
Explanation:

When ressitance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will increases because the resistance of wire decreases due to decrease in length of it. 


Option B is correct.

Sparking occurs when a load is switched off because the circuit has high :

physics static electricity properties of charges charge properties of charge

  1. resistance

  2. inductance

  3. capacitance

  4. impedance

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Correct Option: B
Explanation:

When circuit has high inductance then sparking occurs.


Option B is correct.