Electric Charges and Fields Class 12 Case Study Questions Physics Chapter 1

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Last Updated on September 4, 2024 by XAM CONTENT

Hello students, we are providing case study questions for class 12 physics. Case study questions are the new question format that is introduced in CBSE board. The resources for case study questions are very less. So, to help students we have created chapterwise case study questions for class 12 physics. In this article, you will find case study questions for cbse class 12 physics chapter 1 Electric Charges and Fields.

Chapter	Electric Charges and Fields
Type of Questions	Case Study Questions
Nature of Questions	Competency Based Questions
Board	CBSE
Class	12
Subject	Physics
Unit	Unit 1 Electrostatics
Useful for	Class 12 Studying Students
Answers provided	Yes
Difficulty level	Mentioned
Important Link	Class 12 Physics Chapterwise Case Study

Case Study Questions on Electric Charges and Fields

Questions

Question 1:

Surface charge density is defined as charge per unit surface area of surface charge distribution. i.e., $\sigma=\frac{d q}{d s}$. Two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs having magnitude of $17.0 \times 10^{-22} \mathrm{Cm}^{-2}$ as shown. The intensity of electric field at a point is $E=\frac{\sigma}{\varepsilon_0}$, where $\varepsilon_0=$ permittivity of free space.

(i) $E$ in the outer region of the first plate is
(a) $17 \times 10^{-22} \mathrm{~N} / \mathrm{C}$
(b) $1.5 \times 10^{-25} \mathrm{~N} / \mathrm{C}$
(c) $1.9 \times 10^{-10} \mathrm{~N} / \mathrm{C}$
(d) zero

(ii) $E$ in the outer region of the second plate is
(a) $17 \times 10^{-22} \mathrm{~N} / \mathrm{C}$
(b) $1.5 \times 10^{-15} \mathrm{~N} / \mathrm{C}$
(c) $1.9 \times 10^{-10} \mathrm{~N} / \mathrm{C}$
(d) zero

(iii) $E$ between the plates is
(a) $17 \times 10^{-22} \mathrm{~N} / \mathrm{C}$
(b) $1.5 \times 10^{-15} \mathrm{~N} / \mathrm{C}$
(c) $1.9 \times 10^{-10} \mathrm{~N} / \mathrm{C}$
(d) zero

(iv) The ratio of $E$ from right side of $B$ at distances 2 cm and 4 cm , respectively is
(a) $1: 2$
(b) $2: 1$
(c) $1: 1$
(d) $1: \sqrt{2}$

(v) In order to estimate the electric field due to a thin finite plane metal plate, the Gaussian surface considered is
(a) spherical
(b) cylindrical
(c) straight line
(d) none of these

Answers

(i) Option (d) is correct.

There are two plates $A$ and $B$ having surface charge densities,

$$
\sigma_A=17.0 \times 10^{-22} \mathrm{C} / \mathrm{m}^2
$$

on $A$ and $\sigma_B=-17.0 \times 10^{-22} \mathrm{C} / \mathrm{m}^2$ on $B$, respectively.
According to Gauss’ theorem, if the plates have same surface charge density but having opposite signs, then the electric field in region I is zero.

$$
E_{\mathrm{I}}=E_A+E_B=\frac{\sigma}{2 \varepsilon_0}+\left(-\frac{\sigma}{2 \varepsilon_0}\right)=0
$$

(ii) (d): The electric field in region III is also zero.

$$
E_{\mathrm{III}}=E_A+E_B=\frac{\sigma}{2 \varepsilon_0}+\left(-\frac{\sigma}{2 \varepsilon_0}\right)=0
$$

(iii) (c): In region II or between the plates, the electric field

$$
\begin{aligned}
& E_{\mathrm{II}}=E_A-E_B=\frac{\sigma}{2 \varepsilon_0}+\frac{\sigma}{2 \varepsilon_0} \\
&=\frac{\sigma\left(\sigma_A \text { or } \sigma_B\right)}{\varepsilon_0}=\frac{17.0 \times 10^{-22}}{8.85 \times 10^{-12}} \\
& E=1.9 \times 10^{-10} \mathrm{NC}^{-1}
\end{aligned}
$$

(iv) (c): Since, electric field due to an infinite-plane sheet of charge does not depend on the distance of observation point from the plane sheet of charge. So, for the given distances, the ratio of $E$ will be $1: 1$.

(v) (b): In order to estimate the electric field due to a thin finite plane metal plate, we take a cylindrical cross-sectional area $A$ and length $2 r$ as the gaussian surface.

Also check

Case study questions for other chapters of class 12 physics is given below.

• Electric Charges and Fields Class 12 Case Study Questions Physics Chapter 1
• Case Study Questions for Class 12 Physics

We hope the given case study questions for Electric Charges and Fields Class 12 helps you in your learning.

Topics from which case study questions may be asked

• Electric charges
• Conservation of charge
• Coulomb’s law – force between two-point charges
• Forces between multiple charges
• Superposition principle
• Continuous charge distribution
• Electric field
• Electric field due to a point charge
• Electric field lines
• Electric dipole
• Electric field due to a dipole
• Torque on a dipole in a uniform electric field
• Electric flux
• Statement of Gauss’s theorem
• Applications of Gauss’s theorem to find field due to:
  Infinitely long straight wire
  Uniformly charged infinite plane sheet
  Uniformly charged thin spherical shell (field inside and outside)

Two electric field lines never cross each other. If they intersect, then there will be two directions of electric field at the point of intersection which is not possible.

For further practice on case study questions related to Electric Charges and Fields Class 12 Physics, we recommend exploring the link given below.

Quiz

Topic	Electric Charges and Fields
Useful for	CBSE Class 12 Students
Type of Questions	MCQs, Case Study, Assertion Reason
No. of Questions	45
Solutions	Instant Solutions after Completion of Quiz
Quiz Link	Click here to Take Test
Price	Free

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