physics : class12 Torque and potential energy : Torque on an Electric Dipole : Electrostatics MCQ Questions and Answers
Practice important
Torque and potential energy
MCQ questions and answers.
Page 1
of
1
|
10
MCQ Questions
1. An electric dipole of dipole moment p is placed in a uniform electric field E at an angle theta. What is the magnitude of the torque on the dipole?
A.
pE cos theta
B.
pE sin theta
C.
pE tan theta
D.
pE
Correct Answer:
pE sin theta
Explanation:
The torque on an electric dipole in a uniform electric field is given by tau = pE sin theta, where theta is the angle between the dipole moment and the electric field.
2. When an electric dipole is placed parallel to a uniform electric field, the torque acting on it is:
A.
Maximum
B.
Zero
C.
pE
D.
p/E
Correct Answer:
Zero
Explanation:
For a parallel dipole, theta = 0 degrees. Therefore, tau = pE sin 0 degrees = 0.
3. At what angle between an electric dipole and a uniform electric field is the torque maximum?
A.
0 degrees
B.
30 degrees
C.
90 degrees
D.
180 degrees
Correct Answer:
90 degrees
Explanation:
Torque is tau = pE sin theta. It is maximum when sin theta = 1, which occurs at theta = 90 degrees.
4. The potential energy of an electric dipole of moment p in a uniform electric field E at angle theta is:
A.
pE sin theta
B.
pE cos theta
C.
-pE cos theta
D.
-pE sin theta
Correct Answer:
-pE cos theta
Explanation:
The potential energy of a dipole in a uniform electric field is U = -pE cos theta.
5. What is the potential energy of an electric dipole when it is aligned parallel to a uniform electric field?
A.
pE
B.
-pE
C.
0
D.
2pE
Correct Answer:
-pE
Explanation:
For parallel alignment, theta = 0 degrees. Hence, U = -pE cos 0 degrees = -pE.
6. What is the potential energy of an electric dipole when it is oriented perpendicular to a uniform electric field?
A.
pE
B.
-pE
C.
0
D.
-2pE
Correct Answer:
0
Explanation:
For a perpendicular dipole, theta = 90 degrees. Thus, U = -pE cos 90 degrees = 0.
7. Which orientation of an electric dipole in a uniform electric field corresponds to stable equilibrium?
A.
Dipole antiparallel to the field
B.
Dipole perpendicular to the field
C.
Dipole parallel to the field
D.
Dipole at 45 degrees to the field
Correct Answer:
Dipole parallel to the field
Explanation:
The potential energy is minimum, U = -pE, when the dipole is parallel to the electric field. Minimum potential energy corresponds to stable equilibrium.
8. Which orientation of an electric dipole in a uniform electric field corresponds to unstable equilibrium?
A.
Dipole parallel to the field
B.
Dipole antiparallel to the field
C.
Dipole at 30 degrees to the field
D.
Dipole perpendicular to the field
Correct Answer:
Dipole antiparallel to the field
Explanation:
For an antiparallel dipole, theta = 180 degrees and U = -pE cos 180 degrees = pE, the maximum potential energy. This orientation is unstable equilibrium.
9. If the dipole moment of an electric dipole is doubled while the electric field remains unchanged, its torque at a fixed angle becomes:
A.
Half
B.
Unchanged
C.
Double
D.
Four times
Correct Answer:
Double
Explanation:
Since tau = pE sin theta, torque is directly proportional to the dipole moment p. Doubling p doubles the torque.
10. An electric dipole is rotated from parallel to antiparallel in a uniform electric field. What is the change in its potential energy?
A.
0
B.
pE
C.
2pE
D.
-2pE
Correct Answer:
2pE
Explanation:
Initially, U_parallel = -pE. Finally, U_antiparallel = pE. Therefore, the change in potential energy is pE - (-pE) = 2pE.
Short Questions and Answers
Practice short questions and answers related to
Torque and potential energy
.
Short questions are currently unavailable for this page.