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# Xam Idea Class 12 Physics Chapter 4 Solutions: Moving Charges And Magnetism

Xam Idea Class 12 Physics Solutions for Chapter 4 ‘Moving Charges and Magnetism’ is one of the important chapters for CBSE Class 12 exams. In this chapter of Xam Idea solutions, you will learn about the magnetic field and also about force experienced by a current-carrying conductor inside it. You will also come across various laws of electricity and magnetism like Biot-Savart’s law for current-carrying circular loop, Ampere law for a current-carrying straight wire, etc.

Xam Idea Class 12 Physics Solutions for Chapter 4 Moving Charges and Magnetism include 104 questions that are divided into 4 exercises. These questions include topics like the moving coil galvanometer, its current sensitivity and measuring current and voltage by converting them into ammeter and voltmeter respectively. We have provided stepwise solutions to all the exercise questions for your thorough understanding of the chapter.

Our Xam Idea solutions for Physics are enriched with content which makes them one of the most reliable sources for preparations for CBSE examinations and other engineering entrance examinations such as JEE and NEET. At Instasolv, you will not only get exercise solutions for Xam Idea Class 12 Physics book but also clearer explanations to these questions for free. These solutions are specially designed by highly competent faculties to boost your exam preparations.

## Important topics for Xam Idea Class 12 Physics Solutions Chapter 4: Moving Charges and Magnetism

Magnetic field:

The magnetic field can be described as an area around a magnet, where its magnetic force can be observed. The magnetic fields are represented as lines of force or magnetic flux. In case of a bar magnet, these magnetic lines start from the north pole and end at the south pole. The SI unit for magnetic fields is Tesla (T).

Biot-Savart law:

The Biot-Savart law states that when current flows in a current-carrying conductor, it gives rise to a magnetic field around it. The magnetic field is equal to the sum of the magnetic field generated by the unit element of the current-carrying conductor. The magnetic field is given by:

Ampere’s law

Ampere’s law states that the magnetic field due to current across a current-carrying loop is directly proportional to the current flowing that loop. Hence, it can be stated as:

∫ B.dl =  μo I

Here, μo is the permeability around free space and ∫ B.dl is integral to magnetic field density.

### Force on a Moving Charge Subjected to a Uniform Magnetic Field

In this unit, you will learn about the force experienced by a moving charged particle inside a uniform magnetic field. The magnetic force (F) acting on a charged particle (q) is given by:

F = qVBsinθ

Here, the charged particle is moving at speed of v m/s in a magnetic field strength B with θ inclination.

Cyclotron

Cyclotrons are also known as a particle accelerator, inside a cyclotron the velocity of a particle gets accelerated under the influence of cross electric field and magnetic field (it means the fields are perpendicular to each other).

The charged particle starts its journey at point P, under the influence of the magnetic field it moves in a semi-circular arc between the dees D1 and D2 due to alternating voltage and hence gets accelerated to high velocities. The high-speed charged particle can be received at the exit port.

Force on a Current-Carrying Conductor in a Uniform Magnetic Field

In this section, we will learn and derive an equation for the force acting on a current-carrying conductor in a uniform magnetic field, the force (F) is given by:

F = (nqAvd)LBsinθ

Since, nqAvd = I (by definition of the current)

F=  ILBsinθ

Where L is the length of current-carrying conductors inclined at an angle of θ with the magnetic field with a current I.

### Force Between Two Parallel Current-Carrying Conductors

As we know about the magnetic field due to a current-carrying conductor and about the consequences of external magnetic fields on the current-carrying conductor, thus we can deduce that when two current-carrying conductors are closer to each other the magnetic force will come into action.

### Torque Experienced by a Current-Carrying Loop in a Uniform Magnetic Field

A current-carrying loop with cross-sectional area A and n turns inside the uniform magnetic field (B) with an inclination of θ to it experiences a torque, which is equal to the following equation:

Torque = nBIA.sinθ

Here, I am the current flowing in the given loop

Moving Coil Galvanometer

A moving coil galvanometer is a device used to measure electric current and can even measure current at low orders.

Current Sensitivity: The current sensitivity is given by angle (θ) per unit current (I).

= nAB/k

Here, n is the number of turns across the area (A) and magnetic field strength (B) and k is the coupling factor.

### Exercise Discussion for Xam Idea Class 12 Physics Solutions Chapter 4: Moving Charges and Magnetism

Moving Charges and Magnetism discusses various questions for your exam preparations which are organised across 4 sections: Very short Answer questions, Short answer question-I, Short answer question-II, Long answer questions. The exercises also include PYQ (past years questions) and OIQ (objective inventory questionnaires).

• The section consists of 32 questions which are further divided into two parts: PYQ (11 questions) and OIQ (21 questions).
• The questions asked from these sections come for 2 marks and are basically definition and formula-based numerical.

• In this section, there are 19 questions for you to solve, these questions are again divided into further parts: PYQ (10 questions) and OIQ (9 questions).
• The questions require higher thinking skills and are asked for 4 marks.

• The third section of the exercise comprises a total of 38 questions which consist of two parts: PYQ (24 questions) and OIQ (14 questions).
• The problems consist of tough derivations and numerical problems which you can solve easily applying formulas used in the chapter.
• The questions from these sections are often asked for four marks.