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Electric Charges and Fields

Home / Boards / CBSE / Important Questions / Class 12 / Physics / Electric Charges and Fields

Class 12 Physics Chapter 1
Electric Charges and Fields
Important Questions

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Explore important questions pertaining to class 12 physics electric charges and fields important questions and answers. These particular questions have been designed to help students get ready for the 2024–2025 CBSE Class 12 physics Exam. By interacting with different question types, students will be able to clarify any doubts and make sure they are well prepared for the tests that are coming up. Answering these questions improves confidence and sharpens problem-solving abilities. These electric charges and fields class 12 important questions will help you gain a deeper grasp of the subject by addressing both the most crucial and relevant parts of it.

Introduction

Electric Charges and Fields constitute the foundational principles that underpin much of our understanding of the fundamental forces governing the universe. At its core, this branch of physics explores the behavior of charged particles and the fields they generate, unveiling the intricate interplay between these charges and the surrounding space. The concept of electric charges, whether positive or negative, lays the groundwork for comprehending the profound forces that shape our physical reality. Understanding these charges and the fields they create is pivotal not only in explaining everyday phenomena but also in unlocking the complexities of advanced scientific and technological advancements. In this study, we delve into the class 12th physics chapter 1 electric charges and fields important questions which will clear our understanding of the chapter.

What are Electric Charges and Fields?

Electric Charges refer to inherent properties found in particles, like protons and electrons, creating forces that influence each other. Electric Fields, on the other hand, signify regions around charged objects where this influence extends. These concepts are fundamental in explaining various phenomena, from basic electronics to natural occurrences like lightning, forming the core of theoretical understanding and technological advancements. oswal.io provides electric charges and fields class 12 questions with answers which can help you in preparing for examination.

Class 12 Physics Electric Charges and Fields Important Questions and Answers

Q1. The temperature (T) dependence of resistivity of material A and material B is represented by Fig. (i) and Fig. (ii) respectively. Identify material A and material B.
electric charges and fields class 12 important questions
Options
(a) material A is copper and material B is germanium
(b) material A is germanium and material B is copper
(c) material A is nichrome and material B is germanium
(d) material A is copper and material B is nichrome

Ans. (b) material A is germanium and material B is copper
Explanation:
For semiconductors, there are very few free electrons. The conductor’s resistance decreases as a result of an increase in the number of free electrons that can act as carriers as a result of rising temperature [Fig. (i)]

For a conductor, when temperature rises, more free electrons become available. As a result, more of them begin to oppose one another’s motion, increasing the conductor’s resistance [Fig. (ii)] We know germanium is a semiconductor while copper is a conductor.
So, fig. (i) is a semiconductor while fig. (ii) is a conductor.
Hence, option (b) is correct.

Q2. One metallic sphere A is given positive charge whereas another identical metallic sphere B of exactly same mass as of A is given equal amount of negative charge. Then:
Options
(a) mass of A and mass of B still remain equals and same
(b) mass of A increases
(c) mass of B decreases
(d) mass of B increases

Ans. (d) mass of B increases
Explanation: Negative charge means excess of electrons which increases the mass of sphere B, whereas positive charge on sphere A is given by removal of electrons.

Q3. A conducting sphere of radius 10 cm has unknown charge. If the electric field at a distance 20 cm from the centre of the sphere is 1.2 × 103 NC^{−1} and points radially inwards. The net charge on the sphere is:
Explanation:
Given that,
\begin{array}{l} r=20 \mathrm{~cm}=0.2 \mathrm{~m}, \mathrm{E}=-1.2 \times 10^{3} \mathrm{NC}^{-1} \\[4.5 bp]\because \quad \mathrm{E}=\dfrac{q}{4 \pi \varepsilon_{0} r^{2}} \\[4.5 bp]\therefore \quad q=\left(4 \pi \varepsilon_{0} r^{2}\right) \mathrm{E} \\[4.5 bp]=\dfrac{(0.2)^{2} \times\left(-1.2 \times 10^{3}\right)}{9 \times 10^{9}} \\[4.5 bp]=-5.3 \times 10^{-9} \mathrm{C} \end{array}
Q4. Depict the orientation of the dipole in (i) stable (ii) unstable equilibrium in electric field.

Explanation:

chapter 1 physics class 12 important questions
Q5. Two point charges \text{+ Q}_1\text{ and – Q}_2 are placed r distance apart. Obtain the expression for the amount of work done to place a third charge Q_3 at the midpoint of the line joining two charges.
Explanation:
According to the question
chapter 1 physics class 12 important questions 1

Explanation:
(i) Work done :

\begin{aligned} \mathrm{W} & =\frac{k \mathrm{Q}_{1} \mathrm{Q}_{3}}{r / 2}-\frac{k \mathrm{Q}_{3} \mathrm{Q}_{2}}{r / 2} \\ \mathrm{~W} & =\frac{2 r \mathrm{Q}_{1} \mathrm{Q}_{3}}{r}-\frac{2 r \mathrm{Q}_{3} \mathrm{Q}_{2}}{r} \\ & =\frac{2 r \mathrm{Q}_{3}\left(\mathrm{Q}_{1}-\mathrm{Q}_{2}\right)}{r} \\ & =\frac{2 \mathrm{Q}_{3}\left(\mathrm{Q}_{1}-\mathrm{Q}_{2}\right)}{4 \pi \varepsilon_{0} r}\end{aligned}

CBSE Class 12 Physics Chapter wise Important Questions

Chapter No.Chapter Name
Chapter 1Electric Charges and Fields
Chapter 2Electrostatic Potential and Capacitance
Chapter 3Current Electricity
Chapter 4Moving Charges and Magnetism
Chapter 5Magnetism and Matter
Chapter 6Electromagnetic Induction
Chapter 7Alternating current
Chapter 8Electromagnetic Waves
Chapter 9Ray Optics and Optical Instruments
Chapter 10Wave Optics
Chapter 11Dual Nature of Radiation and Matter
Chapter 12Atoms
Chapter 13Nuclei
Chapter 14Semiconductor Electronics: Materials, Devices and Simple Circuits

Conclusion

Understanding Electric Charges and Fields in Class 12 Physics is crucial to grasp the fundamental principles governing interactions between charged particles and their surrounding space. Platforms like oswal.io offer invaluable resources, class 12 physics chapter 1 important questions These resources aid in comprehensive learning and preparation for mastering this foundational aspect of physics.

Frequently Asked Questions

Ans: Electric charges are fundamental properties of matter, either positive or negative, carried by particles like protons and electrons. Like charges repel, and opposite charges attract each other.
Ans: Coulomb’s Law describes the electrostatic force between two point charges. It states that the force between two charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.
Ans: An electric field exerts a force on charged particles within its influence. The direction of the force on a positive charge aligns with the field, while for a negative charge, it opposes the field’s direction.
Ans: Conductors allow the free movement of charges due to the presence of loosely bound electrons, while insulators restrict charge flow as their electrons are tightly bound.
Ans: Gauss’s Law relates the electric flux through a closed surface to the total charge enclosed within that surface. It is an essential tool to calculate electric fields for symmetrically shaped charged objects.
Chapter Wise Important Questions for CBSE Board Class 12 Physics
Electric Charges and Fields
Electrostatic Potential and Capacitance
Current Electricity
Moving Charges and Magnetism
Magnetism and Matter
Electromagnetic Induction
Alternating current
Electromagnetic Waves
Ray Optics and Optical Instruments
Wave Optics
Dual Nature of Radiation and Matter
Atoms
Nuclei
Semiconductor Electronics: Materials, Devices and Simple Circuits
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