physics : class12 Electric dipole moment : Torque on an Electric Dipole : Electrostatics MCQ Questions and Answers
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Electric dipole moment
MCQ questions and answers.
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MCQ Questions
1. The electric dipole moment of a dipole is defined as the product of:
A.
Electric charge and distance between the charges
B.
Electric charge and electric field
C.
Electric field and distance
D.
Force and distance
Correct Answer:
Electric charge and distance between the charges
Explanation:
The magnitude of electric dipole moment is given by p = qd, where q is the magnitude of either charge and d is the separation between the charges.
2. What is the SI unit of electric dipole moment?
A.
Coulomb per metre
B.
Coulomb metre
C.
Newton per coulomb
D.
Volt per metre
Correct Answer:
Coulomb metre
Explanation:
Since electric dipole moment is p = qd, its SI unit is coulomb multiplied by metre, written as C m.
3. The direction of electric dipole moment is from:
A.
Positive charge to negative charge
B.
Negative charge to positive charge
C.
The midpoint to the positive charge only
D.
The midpoint to the negative charge only
Correct Answer:
Negative charge to positive charge
Explanation:
By convention, the electric dipole moment vector points from the negative charge toward the positive charge.
4. A dipole consists of charges +2 C and −2 C separated by 0.5 m. What is the magnitude of its electric dipole moment?
A.
0.5 C m
B.
1 C m
C.
2 C m
D.
4 C m
Correct Answer:
1 C m
Explanation:
Using p = qd, p = 2 × 0.5 = 1 C m.
5. If the separation between the charges of a dipole is doubled while the charge remains constant, its electric dipole moment becomes:
A.
Half
B.
Unchanged
C.
Double
D.
Four times
Correct Answer:
Double
Explanation:
Because p = qd and q is constant, doubling the separation d doubles the electric dipole moment.
6. If the magnitude of each charge in a dipole is doubled while the separation remains unchanged, the electric dipole moment becomes:
A.
Half
B.
Unchanged
C.
Double
D.
Four times
Correct Answer:
Double
Explanation:
The dipole moment is p = qd. With constant d, doubling q doubles p.
7. The electric dipole moment of a dipole is zero when:
A.
The charges are equal and opposite but separated by a finite distance
B.
The charges have unequal magnitudes
C.
The separation between equal and opposite charges is zero
D.
The dipole is placed in a uniform electric field
Correct Answer:
The separation between equal and opposite charges is zero
Explanation:
For a dipole, p = qd. If the separation d is zero, the dipole moment is zero.
8. A dipole has charges of magnitude 5 × 10⁻⁶ C separated by 2 × 10⁻² m. Its electric dipole moment is:
A.
1 × 10⁻⁸ C m
B.
1 × 10⁻⁷ C m
C.
1 × 10⁻⁶ C m
D.
1 × 10⁻⁴ C m
Correct Answer:
1 × 10⁻⁷ C m
Explanation:
Using p = qd, p = (5 × 10⁻⁶)(2 × 10⁻²) = 10 × 10⁻⁸ = 1 × 10⁻⁷ C m.
9. Electric dipole moment is a:
A.
Scalar quantity
B.
Vector quantity
C.
Dimensionless quantity
D.
Constant with no direction
Correct Answer:
Vector quantity
Explanation:
Electric dipole moment has both magnitude, p = qd, and direction from the negative charge to the positive charge.
10. Two dipoles have the same charge magnitude. Dipole X has charge separation d, and dipole Y has separation 3d. The ratio of their dipole moments pX : pY is:
A.
1 : 1
B.
1 : 2
C.
1 : 3
D.
3 : 1
Correct Answer:
1 : 3
Explanation:
Since p = qd and both dipoles have the same q, their dipole moments are proportional to their separations. Therefore, pX : pY = d : 3d = 1 : 3.
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