physics : class12 Superposition and Electric Dipoles : Superposition Principle : Electrostatics MCQ Questions and Answers
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Superposition and Electric Dipoles
MCQ questions and answers.
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MCQ Questions
1. An electric dipole consists of two equal and opposite charges separated by a small distance. What is the net charge of the dipole?
A.
Positive
B.
Negative
C.
Zero
D.
Depends on the separation
Correct Answer:
Zero
Explanation:
The charges in an electric dipole are equal in magnitude and opposite in sign, so their algebraic sum is zero.
2. The electric dipole moment of a dipole is directed from:
A.
Negative charge to positive charge
B.
Positive charge to negative charge
C.
The midpoint toward the negative charge only
D.
The midpoint in a direction perpendicular to the dipole axis
Correct Answer:
Negative charge to positive charge
Explanation:
By convention, electric dipole moment is directed from the negative charge to the positive charge.
3. Two charges +q and -q are separated by a distance d. What is the magnitude of the dipole moment?
A.
qd
B.
q/d
C.
d/q
D.
2qd
Correct Answer:
qd
Explanation:
The magnitude of the electric dipole moment is p = qd, where q is the magnitude of either charge and d is their separation.
4. At a point on the axial line of an electric dipole, the electric fields due to the two charges are:
A.
In the same direction and add up
B.
In opposite directions and always cancel
C.
Both zero
D.
Perpendicular to each other
Correct Answer:
In the same direction and add up
Explanation:
On the axial line, the fields produced by the positive and negative charges are directed along the same resultant direction, so they combine by superposition.
5. At a point on the equatorial line of an electric dipole, the electric fields due to the two charges are:
A.
In the same direction and perpendicular to the dipole axis
B.
Opposite and unequal, producing a field along the dipole axis
C.
Both directed away from the midpoint
D.
Perpendicular to each other
Correct Answer:
Opposite and unequal, producing a field along the dipole axis
Explanation:
On the equatorial line, the field components perpendicular to the dipole axis cancel, while the components along the dipole axis combine to give a net field.
6. According to the superposition principle, the electric field due to an electric dipole at any point is:
A.
The product of the fields due to its two charges
B.
The vector sum of the fields due to its two charges
C.
The average of the fields due to its two charges
D.
The difference of the charges divided by distance
Correct Answer:
The vector sum of the fields due to its two charges
Explanation:
The superposition principle states that the total electric field is the vector sum of the individual electric fields produced by the positive and negative charges.
7. What happens to the electric dipole moment if the separation between the charges is doubled while their magnitudes remain unchanged?
A.
It becomes half
B.
It remains unchanged
C.
It becomes double
D.
It becomes zero
Correct Answer:
It becomes double
Explanation:
Since p = qd, keeping q constant while doubling d doubles the electric dipole moment.
8. A positive test charge is placed on the axial line beyond the positive charge of an electric dipole. The electric field due to the dipole is directed:
A.
Along the direction of the dipole moment
B.
Opposite to the direction of the dipole moment
C.
Perpendicular to the dipole moment
D.
Always toward the midpoint
Correct Answer:
Along the direction of the dipole moment
Explanation:
On the axial line beyond the positive charge, the resultant electric field is directed from the negative charge toward the positive charge, which is the direction of the dipole moment.
9. The electric field at a point on the equatorial line of a dipole is directed:
A.
Along the dipole moment
B.
Opposite to the dipole moment
C.
Perpendicular to the dipole moment
D.
Away from both charges equally
Correct Answer:
Opposite to the dipole moment
Explanation:
On the equatorial line, the resultant field is along the dipole axis but opposite to the direction of the dipole moment.
10. If the magnitude of each charge in an electric dipole is increased while the separation remains constant, the dipole moment:
A.
Decreases
B.
Increases
C.
Remains zero
D.
Changes direction automatically
Correct Answer:
Increases
Explanation:
The dipole moment is p = qd. With constant separation d, increasing the charge magnitude q increases the magnitude of the dipole moment.
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