Q. If a charge Q is uniformly distributed over a spherical surface of radius R, what is the electric field at a point outside the sphere at a distance r from the center (r > R)?
A.
0
B.
Q/(4πε₀r²)
C.
Q/(4πε₀R²)
D.
Q/(4πε₀R)
Solution
For a point outside the sphere, the electric field behaves as if all the charge were concentrated at the center, hence E = Q/(4πε₀r²).
Q. If the distance between two charges is doubled, how does the force between them change?
A.
It doubles
B.
It halves
C.
It quadruples
D.
It reduces to one-fourth
Solution
According to Coulomb's law, force is inversely proportional to the square of the distance. If the distance is doubled, the force reduces to one-fourth.
Q. If the distance between two charges is halved, how does the force between them change?
A.
It doubles
B.
It quadruples
C.
It remains the same
D.
It halves
Solution
According to Coulomb's law, the force F between two charges is inversely proportional to the square of the distance. If the distance is halved, the force becomes four times greater.
Q. If the electric field at a point is 200 N/C directed towards the positive x-axis, what is the potential difference between two points A and B separated by 3m along the x-axis?
A.
600 V
B.
400 V
C.
200 V
D.
0 V
Solution
V = -E * d = -200 N/C * 3m = -600 V. The potential at B is 600 V lower than at A.
Q. If the electric field at a point is zero, what can be said about the charges producing it?
A.
There are no charges nearby
B.
The charges are equal and opposite
C.
The charges are all positive
D.
The charges are all negative
Solution
The electric field is zero when the vector sum of the electric fields due to all charges is zero, which occurs when there are equal and opposite charges.
Correct Answer:
B
— The charges are equal and opposite
Q. If the electric field due to a charged plane sheet is E, what is the electric field due to two parallel sheets with equal and opposite charge densities?
A.
0
B.
E
C.
2E
D.
E/2
Solution
The fields due to the two sheets add up in the region between them, resulting in a total electric field of 2E.
Electrostatics is a crucial topic in physics that deals with the study of electric charges at rest. Understanding electrostatics is essential for students preparing for school exams and competitive tests, as it forms the foundation for many advanced concepts in physics. Practicing MCQs and objective questions on electrostatics not only enhances conceptual clarity but also boosts your confidence in tackling important questions during exams.
What You Will Practise Here
Fundamental concepts of electric charge and its properties
Understanding Coulomb's Law and its applications
Electric field and electric potential: definitions and calculations
Capacitance and capacitors: types and formulas
Gauss's Law and its significance in electrostatics
Concept of electric dipoles and their behavior in electric fields
Key diagrams and graphical representations related to electrostatics
Exam Relevance
Electrostatics is a significant topic in various exams, including CBSE, State Boards, NEET, and JEE. It frequently appears in the form of conceptual questions, numerical problems, and application-based scenarios. Students can expect to encounter questions that require them to apply Coulomb's Law, calculate electric fields, and analyze capacitor circuits. Familiarity with common question patterns will greatly aid in effective exam preparation.
Common Mistakes Students Make
Confusing the concepts of electric field and electric potential
Misapplying Coulomb's Law in multi-charge systems
Neglecting the direction of electric field lines in problem-solving
Overlooking the significance of units and dimensions in calculations
Failing to understand the behavior of capacitors in series and parallel
FAQs
Question: What is the difference between electric field and electric potential? Answer: The electric field is a vector quantity that represents the force experienced by a unit positive charge, while electric potential is a scalar quantity that indicates the potential energy per unit charge at a point in an electric field.
Question: How do capacitors store energy? Answer: Capacitors store energy in the form of an electric field created between their plates when a voltage is applied across them.
Now is the time to strengthen your understanding of electrostatics! Dive into our practice MCQs and test your knowledge on this vital topic. The more you practice, the better prepared you will be for your exams!
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