Hello students in this session we will learn that how much force and torque an electric dipole experience in external electric field. So lets start…
Electric dipole: A system of two equal and opposite point charges separated by a small distance is called an electric dipole.
Electric dipole moment is equal to the product of the magnitude of either charge and the distance between them. p = q x 2a
Suppose an electric dipole of dipole moment p = qx2a is placed in a uniform electric field E at an angle θ, where θ is the angle between p and E.
A force F1 = qE will act on positive charge in the direction of electric field and force F2 = qE acts on negative charge in opposite direction of electric field.
Here we can see that F1 and F2 are equal in magnitude but opposite in direction.
Hence, F1 + F2 = 0
or Fnet = 0
Thus, net force on a dipole in uniform electric field is zero.
The two equal and opposite forces acting on the dipole form a couple which exerts a torque.
This torque is equal to the magnitude of either force multiplied by the perpendicular distance between the forces.
Thus, the magnitude of torque is τ = pE sinθ.
👉 The direction of torque is perpendicular to the plane of paper inwards. This torque tend to align the dipole axis along the direction of external electric field.
👉 In uniform electric field, dipole experiences torque and net force on dipole is zero. This torque is maximum at θ = 90°. Hence in uniform electric field, dipole experiences rotatory motion.
👉 Note: If θ= 0°, 180° or 360°, then net force and torque on the dipole is zero. So that the dipole exists in equilibrium state.
(i) when θ= 0° or 360°, dipole exists in stable equilibrium state.
(ii) when θ= 180°, dipole exists in unstable equilibrium state.
👉 Note: In non-uniform electric field, dipole experiences torque and net force. Due to which the dipole experiences both rotatory and translatory motion.
For more interesting Videos of Physics follow our YouTube Channel “PHYSICS WITH UMESH RAJORIA“
✅Sharpen Your Pencil ✍️
Q. 1. An electric dipole with dipole moment 4 x 10-9 C-m is aligned at 30° with the direction of a uniform electric field of magnitude 5 x 104 N/C . Calculate the magnitude of the torque acting on the dipole.
Q. 2. An electric dipole will experience a net force when it is placed in
(a) a uniform electric field
(b) a non-uniform electric field
(c) both (a) and (b)
(d) None of these
🔻Comment the Answer💬
Q. 3. An electric dipole is placed at an angle of 30° to a non-uniform electric field. The dipole will experience
(a) a translational force only in the direction of the field
(b) a translational force only in the direction normal to the direction of the field
(c) a torque as well as a translational force
(d) a torque only
🔻Comment the Answer💬
Hello Students,
Physics is the most crucial subject for all the students of class 11th, 12th and also for the students who are preparing for NEET or JEE. Physics is very important to understand many higher level concepts, which are derived from the concepts that we learn in class 11th and 12th.
So better understanding of all the concepts in physics is very necessary, not only to get good marks in physics exam but also to learn physics more effectively.
Get Physics Chemistry & Biology Notes
- 50000+ Students have Ordered so far !
- ⭐⭐⭐⭐⭐ 9.7/10 Average Rating
- Unlimited Access
Grab Everything Now At lowest Price
Just Pay ₹ 99/-
Benefits of Getting Notes e-Books
- Notes covers complete syllabus of Physics Chemistry & Biology for class 10, 11, 12 and NEET/JEE.
- Written in clean and readable handwriting.
- Revised every year with updated syllabus and exam pattern.
- It can save your time and cost which you spend for individual subject coaching.
- Notes are also beneficial at the time of revision.
- Notes are properly indexed with page numbers.
- Special Focus on the topics which carry more weight in exams.
Offer Ends Soon…
Myself Umesh Rajoria and I am a Physics teacher. I have 15 years teaching experience of physics.
You will be happy to know that i have prepared physics notes according to the latest NCERT syllabus for CBSE and other state board students of class 12.
👉These Physics notes for class 12 help the students to understand the concept of Physics easily and retain the formulas and derivations for a longer time.
👉All the diagrams, formulas, derivations and solved numerical are included in these Physics Notes . These notes will be very useful during the preparation of 12th board exams and save most of the time of the students.
🔷 Dear Students,
If You Like the Information and Notes then please Comment and share the post. Which physics topic you want to know please tell us by commenting. I will surely reply your comment. Thanks 🙂
