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# Xam Idea Class 12 Physics Chapter 3 Solutions: Current Electricity

Xam Idea Class 12 Physics Solutions for Chapter 3 ‘Current Electricity’ is an ambient source for CBSE Class 12 board exam preparations. These solutions will provide you with a detailed guide on current and its properties. You will also get to learn about the main concepts of the chapter like how current flows through conductors, its mobility, resistivity, Ohm’s law and Kirchhoff’s law and its applications.

Xam Idea Class 12 Physics Solutions for Current electricity include 103 questions that are divided into 4 different exercises. You will come across various terminologies while solving these questions such as drift velocity, mobility and you will also understand their relationship with an electric current. You will learn about resistors and their combinations and know about cells and potential difference and how to measure it.

Xam Idea Class 12 Physics Solutions are created by our best subject matter experts based on the latest CBSE exam pattern for Class 12. You must refer to our solutions if you are stuck at any of the problems of the chapter or face any difficulty. Our well-curated answers for your problems along with formulas and required explanations will clear all your doubts.

## Important Topics for Xam Idea Class 12 Physics Solutions Chapter 3: Current Electricity

If you are preparing for exams, the following topics in Xam Idea Class 12 Physics Solutions Chapter 3: Current electricity, can be essential for your preparations.

• Electric Current

Electric current is a measure of the flow of charged particles (such as electrons, protons, ions or holes) between two given points. The SI unit in which electric current is measured is called Ampere (A).

• The Flow of Electric Charge in a Metallic Conductor

In a metallic conductor, the current flow due to the flow of free electrons inside it. When there is no external emf applied to it, the net current flowing inside the conductor is zero as the free electrons would flow in a random motion throughout the conductor.

When emf is applied in the conductor, the electric field (set up by the source) accelerates the electrons in the direction of the current which gives them velocity and energy. The rise in energy increases the temperature of the conductor.

• Drift Velocity, Mobility and their Relation with Electric Current

In Xam Idea Class 12 Physics Solutions Chapter 3: Current electricity, you will come across following crucial terminologies related to the chapter.

• Drift velocity:

In case of no electric field in a conductor, the electron flows in randomly, whereas when an electric field is applied, they still move in a random direction but steadily drift in a direction, this velocity is termed as drift velocity. For a current flowing of I amperes across an area of cross-section of A m2 with n electrons of q charge, the drift velocity (v) is given by:

V = I/nAq

• Mobility:

In a conductor, electrons move freely in a random manner. When an electric field is applied, the electrons move toward the positive side of the terminal of the source. Electron mobility refers to the ease of electrons moving quickly towards the positive terminal. The mobility of an electron depends on various things such as drift velocity and also the magnitude of the electric field applied.

The Relation Between Drift velocity and Mobility:

The Drift velocity and mobility for a conductor can be related as:

Mobility = Drift velocity / Electric Field

• Ohm’s law

Ohm’s law states that for a conductor, the ratio of potential difference to the current flowing across the conductor is always constant at a given temperature. This constant is called resistance and is measured in ohm.

• Electrical resistivity

Resistivity or specific electrical resistance is the measure of easiness in passing the electrical current through them. Materials with lower resistivity are terms as conductors whereas that with higher ones are termed as insulators.

The resistivity is measured in ohm-metre and is represented by rho (Ρ).

• Series and parallel combinations of resistors

Resistors can be connected in two possible combinations, i.e. series and parallel.

Series combination

If there are more than one resistors joined together in such a way that there is one way for current to flow, such type of combination of resistors is called a series combination. In series combination, the current remains the same across every

Parallel combination

It is another type of combination of resistors, where there is more than a single path for current to flow. In a parallel connection, the voltage across the resistors remains the same.

• Combination of cells in series and in parallel

Let there be two cells E1 and E2, we can arrange these cells in two possible combinations:

Series:

In series combination, the total emf produced is given by:

= (E1 + E2) + I(r1 + r2)

Parallel:

When two cells are connected in a parallel combination, the net emf generated by such circuit is given by:

= (E1/r1 + E2/r2)/(1/r1+1/r2)

• Kirchhoff’s Laws

Kirchoff’s laws gave two laws related to circuit theory.

Kirchoff’s current law – The first law states that the total current entering the node must be equal to the current flowing out of the node.

Kirchoff’s voltage law – The following law states that the sum of all voltages inside a closed loop is always equal to zero.

Exercise Discussion for Xam Idea Class 12 Physics Solutions Chapter 3: Current Electricity

The exercises for Xam Idea Solutions for Chapter 3: Current Electricity is divided across four sections. Let’s see each of them one by one.

• The section consists of 57 questions with a weightage of 1 mark each.
• The following section comprises two exercises: PYQ (previous year questions) and OIQ (objective inventory questions).
• The exercise includes problems which can be solved by definitions or by applying basic formulas.

• The questions in the following section are easy to solve though you need to get in-depth knowledge about the chapter as the questions to play around formulas in the chapter.
• The section consists of 50 questions (2 marks) which are again divided among two exercises PYQ (previous year questions) and OIQ (objective inventory questions).

• In the following section, there are 36 questions for you to solve.
• You will face problems which require derivations and also hard numerical problems.
• The problems in this section are divided into two parts: PYQ (23 questions) and OIQ (13 questions).