NCERT Solutions for Class 12 Physics Chapter 3 - Current Electricity - PDF Download
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The Class 12 Physics Chapter 3 NCERT Solutions PDF for Current Electricity is now freely available on our website where you can download in pdf form. These solutions are done by subject expert teachers who have years of experience, ensuring that all answers related to the chapter are thoroughly and efficiently explained in a proper and easy way. This chapter is well explained with many experiments and examples. Before getting to the exercise questions, be clear on the basic concepts and refer to the examples explained in the textbook.
Subtopics Covered Under NCERT Solutions for Class 12 Physics Chapter 3 Current Electricity
The topics discussed in the chapter Current electricity are listed below. This chapter completely explained how electricity passes through the conductor, the conductor's response to the electricity, what resistivity is, how cells work, what the cell's response will be when connected in series or parallel, how the current flow is calculated, and all other pertinent information.
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Electric Current
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Electric Currents in Conductors
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Ohm’s law
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Drift of Electrons and the Origin of Resistivity
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Limitations of Ohm’s Law
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Resistivity of Various Materials
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Temperature Dependence of Resistivity
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Electrical Energy, Power
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Combination of Resistors — Series and Parallel
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Cells, emf, Internal Resistance
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Cells in Series and in Parallel
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Kirchhoff’s Rules
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Wheatstone Bridge
Electric Current
Electric current means the flow of electricity in an electronic circuit, and to the amount of electricity flowing through a circuit. Electric current measured in amperes (A). The larger the value in amperes, the more electricity is flowing in the electric circuit.
Electric Currents in Conductors
In this topic, you will know about how electric current passes across conductors. With the help of this section, you will learn that electrical current is nothing but the flow of charge from one point to another. Electric current in conductors is produced because of the flow of electrons. Commonly in an electric circuit, the direction of electric current is taken as the opposite direction of the flow of electrons.
Ohm’s law
Ohm’s law states the relationship between electric current and potential difference. The current that flows through conductors is directly proportional to the voltage applied to it.
Drift of Electrons and the Origin of Resistivity
The drift of electrons and the origin of resistivity start when external power is applied to the conductor. Due to the applied force, the electrons become negatively charged and hence get attracted toward the positive charge. The atoms then take the positive direction when the electrons go away.
Limitations of Ohm’s law:
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Ohm's law is applicable when the temperature of the conductor is constant. Resistivity changes with temperature.
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It does not apply to semiconductors, which do not have a direct current-voltage relationship.
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The relation between voltage and current depends on the sign of voltage.
Resistivity of Various Materials
The materials are classified into three categories: conductors, semiconductors and insulators depending on their resistivities, in an increasing order of their values.Metals have low resistivities. At the other end are insulators like ceramic, rubber and plastics having resistivities greater than metals or more. In between the two are the semiconductors. However, these have resistivity characteristically decreasing with a rise in temperature. The resistivities of semiconductors can be decreased by adding small amount of appropriate impurities.
Temperature Dependence of Resistivity
Resistivity is not directly proportional to the temperature. If there is an increase in the temperature of materials then resistivity of material will decrease. But this is not true for every substance, that means all materials do not have the same dependence on temperature.
Electrical Energy, Power
Electrical power is defined as the work done by the power source to maintain the flow of charge in a circuit. Electrical power is called the rate at which electrical energy is consumed in a circuit per time. SI Units of electrical energy are expressed in joules or watt-sec.
Combination of Resistors — Series and Parallel
A resistor is a two-terminal electrical component device that electrical resistance as a circuit element. Most circuits often have more than one resistor to limit the flow of current in a circuit. There are two simplest combinations of resistors are – series and parallel.
Cells, emf, Internal Resistance
Cells, EMF, Internal Resistance are the basic components which complete the circuit and help the flow of electricity in the circuit. Cells, emf and internal resistance are connected to each other. Batteries i.e. Cells possess internal resistance and potential difference which is voltage.
Cells in Series and in Parallel
Cells are meant to be connected in series when they are joined end to end so that the same quantity of electricity flows through each cell. But on the other hand, cells are connected in parallel when they are joined positive to positive and negative to negative like this current is divided between the cells.
Kirchhoff's Rules
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Kirchhoff's first rule is the junction rule. The sum of all currents entering a junction must equal the sum of all currents leaving the junction.
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Kirchhoff's second rule is the loop rule. The algebraic sum of changes in potential around any closed circuit path (loop) must be zero.
Wheatstone Bridge
The Wheatstone bridge principle says that if four resistances P, Q, R, and S are arranged in a such a way which form a bridge with a cell and key between A and C, and a galvanometer between B and D then the bridge is said to be balanced when the galvanometer reflects a zero deflection.
Key Features of Current Electricity Class 12 Chapter 3 Physics NCERT Solutions
The key features of NCERT Solutions for Class 12 Physics Chapter 3 are the following:
1. The answers are prepared by highly expert Physics teachers.
2. Every important topic is explained in simple language to help you score well in your exams.
3. Students should get a thorough understanding of the important concepts using the NCERT Solutions.
Frequently Asked Questions
Find answers to common questions.
What topics are covered in Class 12 Physics Chapter 3 Current Electricity?
Chapter 3 covers Electric Current, Ohm's Law, Drift of Electrons and Resistivity, Limitations of Ohm's Law, Resistivity of Materials, Temperature Dependence of Resistivity, Electrical Power, Resistor Combinations, Cells and EMF, Kirchhoff's Rules, and the Wheatstone Bridge. These 14 sections form the complete NCERT syllabus for this chapter.
How many questions are there in the NCERT exercise for Class 12 Physics Chapter 3?
The NCERT exercise for Chapter 3 contains 16 questions covering numerical problems and conceptual questions across all major topics — Ohm's Law, resistivity, Kirchhoff's Rules, and circuit combinations. Working through all 16 questions is essential for board exam preparation as questions are frequently repeated or adapted.
What is Kirchhoff's Law in simple terms?
Kirchhoff's Current Law says that the total current entering a junction equals the total current leaving it — charge is conserved. Kirchhoff's Voltage Law says that the sum of all voltages around any closed loop in a circuit equals zero — energy is conserved. Together, these two rules let you solve any circuit network.
What is the balanced condition for a Wheatstone Bridge?
A Wheatstone Bridge is balanced when no current flows through the galvanometer. This occurs when the ratio of the two resistors on one arm equals the ratio on the other arm: P/Q = R/S. At this condition, the galvanometer deflection is zero, and the unknown resistance can be calculated accurately.
Why does resistivity decrease with temperature for semiconductors but increase for metals?
In metals, rising temperature increases atomic vibrations, causing more electron collisions and higher resistivity. In semiconductors, higher temperature frees more electrons from covalent bonds, increasing charge carrier density and reducing resistivity. This opposite temperature behaviour is a defining characteristic of semiconductors and a common exam question.