Q. A charge of +4 µC is placed in a uniform electric field of strength 500 N/C. What is the work done in moving the charge 0.2 m in the direction of the field?
A.
400 J
B.
200 J
C.
100 J
D.
50 J
Solution
W = F * d = (E * q) * d = (500 N/C * 4 × 10^-6 C) * 0.2 m = 0.4 J.
Q. A dipole is placed in a uniform electric field. What is the torque experienced by the dipole? (2023)
A.
pE
B.
pE sin(θ)
C.
pE cos(θ)
D.
Zero
Solution
The torque (τ) experienced by a dipole in a uniform electric field is given by τ = pE sin(θ), where p is the dipole moment and θ is the angle between p and E.
Q. A parallel plate capacitor has a capacitance of 5 µF. If the potential difference across it is increased from 10 V to 20 V, what is the change in stored energy?
A.
25 µJ
B.
50 µJ
C.
75 µJ
D.
100 µJ
Solution
Energy U = 1/2 C V^2. Initial U = 1/2 * 5 × 10^-6 * 10^2 = 0.025 J; Final U = 1/2 * 5 × 10^-6 * 20^2 = 0.1 J. Change = 0.1 - 0.025 = 0.075 J = 75 µJ.
Q. If the charge on a capacitor is doubled, what happens to the energy stored? (2019)
A.
It remains the same
B.
It doubles
C.
It quadruples
D.
It halves
Solution
The energy stored in a capacitor is proportional to the square of the charge (U = Q^2/(2C)). Doubling the charge increases the energy by a factor of 4.
Electrostatics is a crucial topic in physics that deals with the study of electric charges at rest. Understanding this subject is essential for students preparing for school exams and competitive tests. 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 Coulomb's Law
Electric field and electric potential: definitions and calculations
Gauss's Law and its applications in various scenarios
Capacitance: types, formulas, and energy stored in capacitors
Dielectrics and their effect on capacitance
Electrostatic potential energy and its significance
Key diagrams and graphical representations of electric fields
Exam Relevance
Electrostatics is frequently featured in the CBSE syllabus, State Boards, and competitive exams like NEET and JEE. Questions often focus on fundamental concepts, numerical problems, and application-based scenarios. Students can expect a mix of direct questions and conceptual applications, making it essential to practice a variety of MCQs to master this topic.
Common Mistakes Students Make
Confusing electric field strength with electric potential
Misapplying Gauss's Law in complex charge distributions
Overlooking the effect of dielectrics on capacitance
Neglecting units while solving numerical problems
Failing to visualize electric field lines and their properties
FAQs
Question: What is the difference between electric field and electric potential? Answer: The electric field represents the force experienced by a unit positive charge, while electric potential indicates the work done in bringing a unit charge from infinity to a point in the field.
Question: How do capacitors store energy? Answer: Capacitors store energy in the electric field created between their plates when a voltage is applied, which can be calculated using the formula \( \frac{1}{2} CV^2 \).
Now is the time to enhance your understanding of Electrostatics! Dive into our practice MCQs and test your knowledge to excel in your exams. Remember, consistent practice is the key to success!
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