Question

2 Two equal and opposite charges +q and-q are separated by a small distance '2a'. a. Name this arrangement. b. Define its moment. What is its direction? c. If the above system is placed in a spherical shell. What would be the net electric flux coming out of it? d. The above system of two charges is placed in an external electric field E, at an angle 0 with it. Obtain relation for the torque acting on it. (Score: 1+1+1+2) [SAY 2011]​

Answer 1

Answer:

Plus Two Physics Chapter Wise Questions and Answers Chapter 1 Electric Charges and Fields is part of Plus Two Physics Chapter Wise Questions and Answers. Here we have given Plus Two Physics Chapter Wise Questions and Answers Chapter 1 Electric Charges and Fields.

Answer 2

Given:

Two equal and opposite charges +q and-q are separated by a small distance '2a'.

To find:

• Name this arrangement.

• Define its moment. What is its direction?

• If the above system is placed in a spherical shell. What would be the net electric flux coming out of it?

• The above system of two charges is placed in an external electric field E, at an angle 0 with it. Obtain relation for the torque acting on it.

Diagram:

$\boxed{\setlength{\unitlength}{1cm}\begin{picture}(6,4)\put(1,2){\circle*{0.5}}\put(1,2){\line(1,0){4}}\put(5,2){\circle*{0.5}}\put(1,1.5){-q}\put(5,1.5){+q}\put(3,2.5){2a}\put(2.5,2.5){\vector(-1,0){1.75}}\put(3.5,2.5){\vector(1,0){1.75}}\put(1.8,0.5){Electric\:Dipole}\end{picture}}$

Solution:

a) This arrangement of charges is called Electric Dipole

b) The Dipole Moment is a vector directed from the negative charge towards the positive charge.

$\boxed{ \sf{dipole \: moment = P =( q \times 2a)}}$

c) Let net flux be $\phi$.

$\therefore \: \sf{ \phi = \dfrac{ q_{enclosed} }{ \epsilon_{0} } }$

$= > \: \sf{ \phi = \dfrac{ q + ( - q) }{ \epsilon_{0} } }$

$= > \: \sf{ \phi = \dfrac{ 0 }{ \epsilon_{0} } }$

$\boxed{ = > \: \sf{ \phi = 0}}$

d) Let net torque be $\tau$.

$\sf{ \therefore \: \tau = force \times r}$

$\sf{ = > \: \tau = qE\times 2l \sin( \theta) }$

$\sf{ = > \: \tau = q2l \times E \sin( \theta) }$

$\sf{ = > \: \tau = P \times E \times \sin( \theta) }$

$\boxed{ \sf{ = > \: \tau = P E \sin( \theta) }}$

Hope It Helps.