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Chapter Analysis
Intermediate24 pages • EnglishQuick Summary
The chapter 'Current Electricity' from Class 12 Physics primarily delves into the flow of electric charges in a conductor. It explains the concepts of electric current, and discusses Ohm's Law in detail, including its applications and limitations. The chapter then explores the topics of electrical energy and power, resistivity, and the series and parallel combination of resistors and cells. It also introduces key principles like Kirchhoff's rules and discusses devices like the Wheatstone bridge for measuring resistances.
Key Topics
- •Electric current and its calculation
- •Ohm's Law and its applications
- •Resistivity and conductivity of materials
- •Repulsions and series/parallel combinations
- •Kirchhoff's rules
- •Wheatstone bridge
- •Electrical energy and power
- •Temperature dependence of resistance
Learning Objectives
- ✓Understand the concept and calculation of electric current
- ✓Apply Ohm's Law to solve electrical problems
- ✓Differentiate between series and parallel circuits
- ✓Apply Kirchhoff's rules for complex circuits
- ✓Analyze the temperature's effect on resistivity
- ✓Use a Wheatstone bridge to find unknown resistances
Questions in Chapter
The storage battery of a car has an emf of 12 V. If the internal resistance of the battery is 0.4 Ω, what is the maximum current that can be drawn from the battery?
Answer: The maximum current, I=EMF/R=12V/0.4Ω=30A
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A battery of emf 10 V and internal resistance 3 Ω is connected to a resistor. If the current in the circuit is 0.5 A, what is the resistance of the resistor? What is the terminal voltage of the battery when the circuit is closed?
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Additional Practice Questions
Explain the impact of temperature on the resistivity of conductors and semiconductors.
mediumAnswer: For conductors, resistivity increases with temperature due to increased collisions among charge carriers. In contrast, the resistivity of semiconductors decreases with temperature as more charge carriers are made available due to thermal generation.
Describe how Kirchhoff's Loop Rule is applied in solving circuit problems.
mediumAnswer: Kirchhoff's Loop Rule states that the algebraic sum of all voltage differences around any closed loop must equal zero. This principle helps to calculate unknown voltages or currents in complex circuits by setting up a system of equations based on the loops considered.
What is drift velocity and how is it related to electric current?
hardAnswer: Drift velocity is the average velocity attained by charged particles, such as electrons, in a material due to an electric field. It is directly proportional to the current flowing through the conductor and inversely proportional to the charge and cross-sectional area of the conductor.
Discuss briefly how the Wheatstone bridge works.
mediumAnswer: The Wheatstone bridge is used to measure unknown resistances. It consists of four resistors in a diamond shape and a galvanometer between two diagonally opposite points. By adjusting known resistances until no current flows through the galvanometer, the resistance ratio is balanced and the unknown resistance can be determined.
Why does the internal resistance of a battery impact its terminal voltage?
easyAnswer: Internal resistance causes a voltage drop inside the battery when current flows, reducing the terminal voltage observed across the battery's terminals from its emf value.