Tag: electric fields

Quizzes (2) Questions (64)

Questions Related to electric fields

Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

There are two charges $+2\mu\ C\ and -3\mu\ C$. The ratio of forces acting on them will be 

  1. $2:3$

  2. $1:1$

  3. $3:2$

  4. $4:9$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

There are two charges $+2\mu C$ and $-3\mu C$. The ratio of forces acting on them will be $F=\dfrac { { q } _{ 1 }{ q } _{ 2 }K }{ { r }^{ 2 } } $

$\dfrac { { F } _{ 1 } }{ { F } _{ 2 } } =\dfrac { { q } _{ 2 } }{ { q } _{ 1 } } =\dfrac { 3 }{ 2 } $ or  ${ F } _{ 1 }:{ F } _{ 2 }=3:2$

Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

A light beam travelling in the x-direction is described by the electric field ${ E } _{ y }=(300V{ m }^{ -1 })sin\quad \omega (t-x/c).$ An electron is constrained to move along the y-direction with a speed of $2.0\times  {10}^7 { m }^{ -1 }$ Find the maximum electric force and the maximum magnetic force on the electron

  1. $4.8\times {10}^{-17} N, zero$

  2. $4.2\times {10}^{-18} N, 1.8\times 10^{-8}N$

  3. $4.8\times {10}^{-17} N, 3.2\times 10^{-18}N$

  4. Zero, Zero
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
A light beam travelling 
${ E } _{ y }=\left( 300V/m \right) sinw\left( t-x/c \right) $.
$V=2.0\times { 10 }^{ 7 }{ m }^{ -1 }$
${ B } _{ 0 }=\dfrac { { F } _{ 0 } }{ C } =\dfrac { 300 }{ 2\times { 10 }^{ 7 } } =150\times { 10 }^{ -7 }T$
${ F } _{ m }={ B } _{ 0 }qV$
       $=9.1\times { 10 }^{ -31 }\times 150\times { 10 }^{ -7 }\times 2\times { 10 }^{ 7 }$
       $=2.8\times { 10 }^{ -28 }\times 2$
       $=4.8\times { 10 }^{ -17 }N$
magnetic force $=0$
because they are perpendicular to each other.
Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

Two charges Q and -2Q are placed at some distance. the locus of points in the plane of the charges where the potential is zero will be

  1. Straight line

  2. Circle

  3. Parabola

  4. ellipse
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Two charges $Q$, $-2Q$
some distance
Potential $=0$
hence,
$\dfrac { 1 }{ 4\pi { \epsilon  } _{ 0 } } \times \dfrac { Q\times \left( -2Q \right)  }{ R } =0$
When we use it the parabolic condition then,
${ y }^{ 2 }=4ax\quad \longrightarrow \left( 1 \right) $
Now,
$\dfrac { 1 }{ 4\pi { \epsilon  } _{ 0 } } \times \dfrac { Q\times 2Q }{ R } =0$
$\dfrac { { 2Q }^{ 2 } }{ R } =0\quad \longrightarrow \left( 2 \right) $
Hence, equating $(1)$ and $(2)$ and we get, the system is getting parabola.
Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

Force of attraction between two point charges $Q$ and $-Q$ separated by $d$ meter is $F _e$. When these charges are placed two identical sphere of radius $R=0.3\ d$ whose centries are $d$ meter apart the force of attraction between them is 

  1. Greater than $F _{e}$

  2. Equal to $F _{e}$

  3. Less than $F _{e}$

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

Force of attraction between two point charges $Q$ and $-Q$ separated by $d$.

Force ${ F } _{ e }$
radius $=R=3d$
That is also equal to ${ F } _{ e }$ because the distance is same hence force is also same.

Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

Two lithium nuclei in a lithium vapour at room temperature do not combine to form a carbon nucleus- because:

  1. a lithium nucleus is more tightly bound than a carbon nucleus

  2. carbon nucleus is unstable particle

  3. it is not energetically favourable

  4. coulomb repulsion does not allow the nuclei to come very close
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Two lithium nuclei in a lithium vapor can combine only if vapor is heated to a very high temperature. so that the nuclei acquire high kinetic energy to penetrate the coulomb barrier. The vapor is also compressed to a very high pressure.

Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

When a negatively charged ebonite rod is brought near a negatively charged and freely suspended ball, then the ball :

  1. gets repelled

  2. attracted

  3. is not affected

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

When two like charges are brought closer, they repel and when two unlike charges are brought closer, they attract each other.
Hence, when a negatively charged ebonite rod is brought near a negatively charged and freely suspended ball, then the ball gets repelled.

Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

When a comb is rubbed with hair, it attracts paper bits. Choose the right explanation:

  1. Bits of paper gets attracted due to gravitational force

  2. Due to electromagnetic effect, bits of paper are attracted

  3. Comb gets charged by friction and attracts bits of paper

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

When comb is rubbed to hair, it induces negative charge due to friction. When it is brought close to paper bits, they get polarized and the positive part sticks to the comb due to electrostatic attraction. 

Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

In the thunderstorm, the charges accumulate near the upper edges of clouds are

  1. negatively charged

  2. positively charged

  3. neutral

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

We have to find the nature of charges on upper edges of clouds in a thunderstorm, the air currents move upwards while the water droplets move downward. This vigorous movement causes separation of charges. This leads to the positive charges collected near the upper edges of clouds and the negative charges to accumulate near the lower edges of the clouds.

Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

Charge 1 attracts Charge 2, Charge 2 repels Charge 3, and Charge 3 attracts Charge 4. Which of the following option must hold good for the given condition of four point charges? 

  1. Charge 1 attracts Charge 4

  2. Charge 2 attracts Charge 3

  3. Charge 1 repels Charge 3

  4. Charge 2 repels Charge 4

  5. Charge 1 repels Charge 4
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

If charge 1 is positive and charge 2 is negative, then charge 1 and 2  will attract. As charge 2 and 3 repels so charge 3 should be negative. Since charge 3 and 4 attracts so charge 4 should be positive. Thus, charge 1 and 4 both are same charge so they will repel. If you take charge 1 is negative and 2 is positive similarly you get 4 is negative so 1 and 4 both have same charge.