Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics magnetic fields and electromagnetism contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

$F _g$ and $F _e$ represent gravitational and electrostatic force respectively between electrons situated at a distance $0.1\,m. F _g/F _e$ is of the order

  1. $10^{-41}$
  2. $10^{-45}$
  3. $10^{40}$
  4. $10^{-42}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
${ F } _{ y }$ and ${ F } _{ e }$ represent gravitational and electrostatic force respectively between electrons situated at a distance $=0.1m$
let, us take the ratio
$\dfrac { { F } _{ e } }{ { F } _{ g } } =\dfrac { \dfrac { 1 }{ 4\pi { \epsilon  } _{ 0 } } \dfrac { { q }^{ 2 } }{ { d }^{ 2 } }  }{ G\dfrac { { m }^{ 2 } }{ { d }^{ 2 } }  } $
$\dfrac { { F } _{ e } }{ { F } _{ g } } =\dfrac { 1 }{ 4\pi { \epsilon  } _{ 0 } } \times \dfrac { 1 }{ G } \times \dfrac { { q }^{ 2 } }{ { m }^{ 2 } } $
$\dfrac { { F } _{ e } }{ { F } _{ g } } =9\times { 10 }^{ 9 }\times \dfrac { 1 }{ 6.67\times { 10 }^{ -11 } } \times \dfrac { { \left( 1.6\times { 10 }^{ -19 } \right)  }^{ 2 } }{ { \left( 9.1\times { 10 }^{ -31 } \right)  }^{ 2 } } $
$\Rightarrow \dfrac { { F } _{ e } }{ { F } _{ g } } =4.17\times { 10 }^{ 42 }$
or,  $\dfrac { { F } _{ e } }{ { F } _{ g } } $ is of the order of ${ 10 }^{ -42 }$.
Multiple choice physics magnetic fields and electromagnetism contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

Four point charge of $+10^{-7}C, -10^{-7}C, -2\times 10^{-7}C$ and $+2\times 10^{-7}C$ are placed respectively at the corners $A, B, C, D$ of a $0.05\ m$ square. Find the magnitude of the resultant force on the charge at $D$.

  1. $0.2\ dyne$
  2. $0.2\ newton$
  3. $2\ dyne$
  4. $0.02\ newton$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics magnetic fields and electromagnetism contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

An $\alpha$-particle is the nucleus of a helium atom. It has a mass $m=6.64 \times 10^{-27}$kg and a charge $q = + 2e =  3.2 \times 10^{-19}$ C. Compare the force of the electric repulsion between two a-particles with the force of gravitational attraction between them.

  1. $\displaystyle \dfrac{F _e}{F _g} = 3.1 \times 10^{32}$
  2. $\displaystyle \dfrac{F _e}{F _g} = 3.1 \times 10^{35}$
  3. $\displaystyle \dfrac{F _e}{F _g} = 3.1 \times 10^{38}$
  4. $\displaystyle \dfrac{F _e}{F _g} = 1 \times 10^{32}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electrostatic repulsion = $F _e=\dfrac{1}{4 \pi \epsilon } \dfrac{q^2}{r^2 }=\dfrac{1}{4 \pi \epsilon } \dfrac{4e^2}{r^2 } $

gravitational attraction = $ F _g = G\dfrac{m^2}{r^2} $

$\dfrac{F _e}{F _g} = \dfrac{1}{4 \pi \epsilon } \dfrac{4 e^2}{G m^2} = 3.1 \times 10^{35} $

Multiple choice physics magnetic fields and electromagnetism contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

Electrostatic force and gravitational force differ in which respect?

  1. Conservative force

  2. Central force

  3. Principle of superposition

  4. Dependence on the intervening medium
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In electrostatic force, the force of medium depend on charges while the force of medium due to gravity does not depend on masses. There is no concept of induced mass.

Multiple choice physics magnetic fields and electromagnetism contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

The ratio of electric force between two electrons to the gravitational force between them is of the order

  1. 10$^{42}$
  2. 10$^{39}$
  3. 10$^{36}$

  4. 1
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The electric force between two electrons is $F _e=\dfrac{ke^2}{r^2}$

and gravitational force between two electrons is $F _g=\dfrac{Gm _e^2}{r^2}$
Thus, $\dfrac{F _e}{F _g}=\dfrac{ke^2}{Gm _e^2}=\dfrac{(9\times 10^9)(1.6\times 10^{-19})^2}{(6.67\times 10^{-11})(9.1\times 10^{-31})^2}=4.17\times 10^{42} \sim 10^{42}$

Multiple choice physics primary concept of force and energy contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

When an object is rubbed with some materials, it acquires charges and becomes ________ object.

  1. uncharged

  2. charged

  3. neutral

  4. heavy
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When object is rubbed with some materials it acquires charges. This object is called as charged object and develops electrostatic force.

Multiple choice physics primary concept of force and energy contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

Under action of which force does water flow from an open tap towards ground?

  1. Electrostatic force

  2. Magnetic force

  3. Gravitational force

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Objects tend to move downwards to the earth because of gravity of the earth. This force, exerted on the object is known as force of gravity. 

Multiple choice physics primary concept of force and energy contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

Does moon have its own gravity?

  1. No

  2. Yes

  3. Not known yet

  4. Only during full moon
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Gravity is not a property of the earth alone. Every object in the universe exerts a force on every other object. This is called gravitational force. Naturally, moon also has its own gravity.