Current Electricity Class 12 Case Study Questions Physics Chapter 3

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Last Updated on December 26, 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 3 Current Electricity.

Chapter	Current Electricity
Type of Questions	Case Study Questions
Nature of Questions	Competency Based Questions
Board	CBSE
Class	12
Subject	Physics
Unit	Unit 2 Current Electricity
Useful for	Class 12 Studying Students
Answers provided	Yes
Difficulty level	Mentioned
Important Link	Class 12 Physics Chapterwise Case Study

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Table of Contents

Case Study Questions on Current Electricity

Questions

Question 1:

Emf of a cell is the maximum potential difference between two electrodes of the cell when no current is drawn from the cell. Internal resistance is the resistance offered by the electrolyte of a cell when the electric current flows through it. The internal resistance of a cell depends upon the following factors:
(i) distance between the electrodes,
(ii) nature and temperature of the electrolyte,
(iii) nature of electrodes and
(iv) area of electrodes.
For a freshly prepared cell, the value of internal resistance is generally low and goes on increasing as the cell is put to more and more use. The potential difference between the two electrodes of a cell in a closed circuit is called terminal potential difference and its value is always less than the emf of the cell in a closed circuit. It can be written as $V=\varepsilon-I r$.

Read the given passage carefully and give the answer of the following questions:

Q 1. Acell of emf $E$ and internal resistance $r$ is connected across a resistance $R$. If internal resistance is equal to $R$, what will be the potential difference between the terminals of the cell?

Q 2. A cell of emf $E$ and internal resistance $r$ give a current of 0.5 A with an external resistance of $12 \Omega$ and a current of 0.25 A with an external resistance of $25 \Omega$. What is the value of internal resistance of the cell?

Q 3. Two batteries of emfs 2 V and 1 V of internal resistances $1 \Omega$ and $2 \Omega$ respectively are connected in parallel. What is the effective emf of the combination?

Q 4. An external resistance $R$ is connected to a cell of internal resistance $r$. At which condition, the maximum current flows in the external resistance?

Q 5. If external resistance connected to a cell has been increased to 5 times, the potential difference across the terminals of the cell increases from 10 V to 30 V . Then what will be the value of the emf of the cell?

Answers

1.
$$
\begin{aligned}
&\begin{aligned}
E & =I(R+r) \text { and } V=I R \\
\Rightarrow \frac{V}{E} & =\frac{R}{R+r}=\frac{R}{R+R}=\frac{1}{2} \Rightarrow V=\frac{E}{2}
\end{aligned}
\end{aligned}
$$

$$
E=I(R+r)
$$

In first case, $\quad I=0.5 \mathrm{~A} ; R=12 \Omega$

$$
E=6.0+0.5 r ….(1)
$$

In second case, $I=0.25 A ; R=25 \Omega$

$$
E=6.25+0.25 r …(2)
$$

From eqs. (1) and (2), $r=1 \Omega$

3. In parallel combination of cells,

$$
E_{e q}=\frac{E_1 r_2+E_2 r_1}{r_1+r_2}
$$

Here $E_1=2 \mathrm{~V}, E_2=1 \mathrm{~V}, r_1=1 \Omega, r_2=2 \Omega$

$$
\therefore \quad E_{e q}=\frac{2 \times 2+1 \times 1}{1+2}=\frac{5}{3} V
$$

4. Current in the circuit, $I=\frac{E}{R+r}$
or

$$
\begin{aligned}
& I=\frac{E}{\sqrt{(R-r)^2+4 r R}} \\
& \quad\left[\because R+r=\sqrt{(R-r)^2+4 R r}\right]
\end{aligned}
$$

Obviously I will be maximum if denominator is minimum, for which we must have

$$
\begin{aligned}
R-r & =0 \\
R & =r
\end{aligned}
$$

or
When $R=r$, then maximum current will flow in the external resistance.

5. For first case, $\frac{E}{R+r}=\frac{10}{R}$

For second case, $\frac{E}{5 R+r}=\frac{30}{5 R}$
Dividing above equations, we get, $r=5 R$
From eq. (1),

$$
\begin{aligned}
\frac{E}{R+5 R} & =\frac{10}{R} \\
E & =60 \mathrm{~V}
\end{aligned}
$$

Also check

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

We hope the given case study questions for Current Electricity Class 12 helps you in your learning.

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Topics from which case study questions may be asked

Electric Current and Flow of Electric Charges
Drift Velocity, Mobility, and Their Relation with Electric Current
Ohm’s Law
V-I Characteristics (Linear and Non-linear)
Electrical Energy and Power
Electrical Resistivity and Conductivity
Temperature Dependence of Resistance
Internal Resistance of a Cell
Potential Difference and EMF of a Cell
Combination of Cells in Series and Parallel
Kirchhoff’s Rules
Wheatstone Bridge

Drift velocity is directly proportional to the relaxation time of the electrons.

For further practice on case study questions related to Current Electricity Class 12 Physics, we recommend exploring the link given below.

Practice More Case Study Questions on “Current Electricity”

Frequently Asked Questions (FAQs) on Current Electricity Case Study Questions

Q1: What are case study questions for CBSE examinations?

A1: Case study questions in CBSE examinations typically involve scenarios or real-life examples, requiring students to apply their understanding of concepts to solve problems or analyze situations.

Q2: Why are case study questions important for understanding class 12 physics chapters?

A2: Case study questions provide a practical context for students to apply theoretical knowledge to real-world situations, fostering deeper understanding and critical thinking skills.

Q3: How should students approach answering case study questions for CBSE?

A3: Students should carefully read the case study, identify the key issues or problems presented, analyze the information provided, apply relevant concepts and principles of chemical reactions and equations, and formulate well-supported solutions or responses.

Q4: Are there any resources available online for students to practice case study questions on class 12 physics chapters for CBSE exams?

A4: Yes, several educational websites offer case study questions for CBSE students preparing for science examinations. We also offer a collection of case study questions for all classes and subject on our website. Visit our website to access these questions and enhance your learning experience. If you need more case study questions for your preparation, then you visit Physics Gurukul website.

Q5: How can students effectively prepare for case study questions on “Current Electricity” for CBSE exams?

A5: Effective preparation strategies include regular revision of concepts, solving practice questions, analyzing case studies from previous exams, seeking clarification on doubts, and consulting with teachers or peers for guidance and support.

Q6: How can teachers incorporate case study questions on “Current Electricity” class 12 physics into classroom teaching?

A6: Teachers can integrate case studies into lesson plans, group discussions, or interactive activities to engage students in active learning, promote problem-solving skills, and facilitate a deeper understanding of “Current Electricity”.

Q7: How is the drift velocity in a conductor affected with the rise in temperature?

A7: The drift velocity in a conductor decreases with increase in temperature.

Q8: Why alloys like Constantan and Manganin are used for making standard resistors?

A8: Alloys like Constantan and Manganin are used for making standard resistors because the resistivity of these alloys has lesser dependence on the temperature.

Q9: Give the condition under which the Wheatstone bridge is said to be most sensitive

A9: The Wheatstone bridge is most sensitive, when the null point is achieved near the midpoint of the wire

Q10: It is easier to confine electric currents to a definite path than to direct heat flow along definite routes
using heat insulators. Why?

A10: The ratio of resistivity of electrical insulator and electrical conductor is of the order of 10²², whereas that of thermal insulator and thermal conductor is of the order of 10³.

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