physics : class12 Limitations of Coulomb Law Applications : Superposition Principle : Electrostatics MCQ Questions and Answers
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Limitations of Coulomb Law Applications
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MCQ Questions
1. Coulomb's law in its simple form is most directly applicable to which type of charge distribution?
A.
A point charge
B.
A uniformly charged irregular object
C.
A changing current
D.
A magnetic pole
Correct Answer:
A point charge
Explanation:
The simple form of Coulomb's law gives the force between two point charges. Extended charge distributions require dividing them into small elements and applying superposition.
2. Why can Coulomb's law not usually be applied directly between the centers of two extended charged bodies?
A.
Their total charges may be distributed over different points
B.
Electric charge has no effect outside a body
C.
The force between charges is always zero
D.
The distance between their centers is always unknown
Correct Answer:
Their total charges may be distributed over different points
Explanation:
For extended bodies, different parts of one body interact with different parts of the other. The center-to-center formula is valid only in special symmetric cases.
3. Coulomb's law for two point charges is generally used under which condition?
A.
The charges are stationary
B.
The charges are moving with changing speed
C.
The charges are inside a magnetic field only
D.
The charges are always neutral
Correct Answer:
The charges are stationary
Explanation:
The electrostatic form of Coulomb's law applies to stationary charges. Moving or accelerating charges may require additional electromagnetic effects.
4. When calculating the force due to a continuous charged body, what is usually required?
A.
Integration of the effects of small charge elements
B.
Ignoring the charge distribution
C.
Using only the nearest charge element
D.
Replacing the charge by a magnetic field
Correct Answer:
Integration of the effects of small charge elements
Explanation:
A continuous charge distribution contains many small charge elements. Their individual forces are added using superposition, usually through integration.
5. The simple inverse-square form of Coulomb's law is most suitable for charges in which environment?
A.
Vacuum or a uniform medium
B.
A medium whose properties change randomly from point to point
C.
A region containing only magnetic charges
D.
A region with no electric charges at all
Correct Answer:
Vacuum or a uniform medium
Explanation:
The usual form of Coulomb's law is directly used in vacuum and can be adapted to a uniform medium using its permittivity. Nonuniform media can alter the field distribution.
6. For a uniformly charged spherical shell, Coulomb's law can be used outside the shell as if the charge were concentrated at its center because of which condition?
A.
Spherical symmetry
B.
The shell has no charge
C.
The shell is always conducting
D.
The force law does not depend on distance
Correct Answer:
Spherical symmetry
Explanation:
Spherical symmetry allows the external field of a uniformly charged spherical shell to be treated as if its total charge were concentrated at the center. This is a special case, not a general rule for extended bodies.
7. Which situation is outside the direct scope of electrostatic Coulomb's law?
A.
Two charges fixed at rest
B.
Two stationary point charges in vacuum
C.
Charges changing position rapidly with time
D.
A stationary charge near another stationary charge
Correct Answer:
Charges changing position rapidly with time
Explanation:
Coulomb's law in electrostatics describes stationary charges. Rapidly moving or accelerating charges involve magnetic and radiation effects that are not included in the simple electrostatic law.
8. For an irregularly shaped charged object, why is replacing the whole object by a point charge at its center generally inaccurate?
A.
The charge distribution is not sufficiently symmetric
B.
The object cannot possess electric charge
C.
The electric force is independent of charge
D.
The center of the object has no position
Correct Answer:
The charge distribution is not sufficiently symmetric
Explanation:
For an irregular object, the positions of its charge elements matter. Treating all charge as located at the center is generally valid only when symmetry makes that replacement accurate.
9. When several point charges are present, what limitation should be remembered while applying Coulomb's law?
A.
The force must be found by adding the individual force vectors
B.
Only the largest charge produces a force
C.
All forces cancel automatically
D.
The charges must be replaced by magnetic poles
Correct Answer:
The force must be found by adding the individual force vectors
Explanation:
Coulomb's law gives the force between a pair of charges. For several charges, superposition requires vector addition of all individual forces.
10. Which statement describes a limitation of using Coulomb's law for charge distributions?
A.
A single center-to-center formula is not generally valid for arbitrary shapes
B.
Coulomb's law applies only when charges have equal magnitude
C.
Coulomb's law cannot describe attraction
D.
Coulomb's law is independent of the medium
Correct Answer:
A single center-to-center formula is not generally valid for arbitrary shapes
Explanation:
For arbitrary extended charge distributions, the force depends on the locations of all charge elements. Therefore, the simple point-charge formula cannot generally be used with only the centers and total charges.
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