40. Class 12 Physics | Electric Potential | Electric Dipole Placed in a Uniform Field | (GA)

# 40. Class 12 Physics | Electric Potential | Electric Dipole Placed in a Uniform Field | (GA)

lets discuss. about what happen when electric
dipole is placed in, a uniform electric field. we know that uniform, electric field is a
situation where all electric lines of forces are. parallel and equi-distance from each
other. and here if we place a dipole just for, understanding in sake of simplicity i
am drawing, an enlarged we of a dipole. and say this is plus q and this minus q charge,
and this is the direction of dipole moment. which is placed. and dipole moment is making
an angle theta with the direction of, electric field vector. in this situation we know when
the dipole is placed in an electric field. the positive charge of dipole will experience
a force which is q-e in the direction of field. and negative charge being negative it’ll
experience a force q-e in the direction opposite to, the direction of field. and, as the dipole
itself is a system. and in all it is experiencing 1 force forward 1 backward so the net force
acting on the dipole in uniform electric field we can directly state it should be zero. must
be zero so we can say directly we can write. net force. on a dipole. placed, in a uniform.
electric field is this net force is equal to. zero. because, equal and opposite charges
will experience equal and opposite forces. but here we can see that these 2 forces are
not acting along this same line. so we can write. as. the 2 equal forces. are not acting.
along same line of action. these will produce. a couple. and we know that. the couple is
a torque. acting in the same direction due to both of these forces which is independent
of the. location of axis of rotation. so we can write down the value of torque as. in
case of couple it is defined as force multiplied by. separation between. lines of action of
forces. so here the magnitude of torque can be given as force which is q-e multiplied
by. the separation between the 2 lines here we can write as d sine theta because d is
the separation between charges and, theta is the angle between, the line joining charges
of dipole and electric field. so it’ll be d sine theta. and here we can write q d as
p so. torque can be written as p e sine theta where. p is the dipole moment, of this dipole
in electric field. and vectorially, this expression can be written as torque is equal to, p cross
e. both of these results are useful forever. for their applications. so just keep in mind
that. the torque acting on dipole depends on its dipole moment electric field and the
orientation of dipole that is the angle between dipole moment and the electric field.

## 14 Replies to “40. Class 12 Physics | Electric Potential | Electric Dipole Placed in a Uniform Field | (GA)”

1. cpratham3 says:

why positive charge will feel a force in the direction of the electric field?

2. Ayush Mishra says:

Sir will the dipole flip by 180° if – charge is in right side and + on left side.And Electrical Field is from left to right?
Thanks

3. Johnaton Mark says:

Why are attractive forces between the positive and negative charges not considered?

4. sathish shankar says:

but why sin teta..why not cos teta

5. Shahbaaz Ahmed says:

you have put that theta wrongly in vid

6. Pranjal Pandey says:

Thankuu sir 😍

7. sanjeev kumar says:

Thanks sir for ur simple explanation

8. Harpreet Kaur says:

Nice voice

9. apppu vysh says:

GOT A GOOD IDEA FOR LIFE TIME😄😄

10. Dr. Sachin Sharma says:

Thanks you very much

11. Ajay Ganesh says:

In my 12th book p=2qd given
But here p=qd
which is correct sir

12. Golu Yadav says:

Vry nyc explanation sir.

13. ABHISHEK SHARMA says:

Sir why can't the distance between two charges be d , why to take dsin theta

14. Arshmera Veer says:

Hi james bond