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NCERT Solutions for Class 12 Physics Chapter 4 Moving Charges and Magnetism 4.1 A circular coil of wire consisting of 100 turns, each of radius 8.0 cm carries a current of 0.40 A. What is the magnitude of the magnetic field B at the centre of the coil? Solution :   Given , n = 100 , r = 8 cm = 0.08m , I = 0.4 A  Magnitude of the magnetic field at the centre of the coil is given by the relation, $$\left | B \right | = \frac{\mu_{0} }{4\pi }.\frac{2\pi nI}{r}$$ where $\mu_{0} =4\pi \times10^{-7}TmA^{-1}$ $$B = \frac{4\pi \times 10^{-7}}{4\pi }.\frac{2\pi \times 100 \times 0.4}{0.08}$$ $$B = 10^{-7}. \frac{2\pi \times 10^{2} \times 4 \times 10^{-1} }{8 \times 10^{-2}}$$ $$B = \frac{2\pi \times 4}{8}.\frac{10^{-7} \times 10^{^{2}} \times 10^{-1}}{10^{-2}}$$ $$B = \pi \times 10^{-7+2-1+2}$$ $$B = 3.14 \times 10^{-4}T$$ 4.2 A long straight wire carries a current of 35 A. What is the magnitude of the field B at a point 20 cm from the wire? Solution :  Given I = 35 A , r = 20 cm ...

Ampere's Circuital Law :   Ampere Circuital Law states that the line integral of the magnetic field around any closed path in free space is equal to absolute permeability ($\mu_{0}$) times the net current passing through any surface enclosed by the closed path.  Mathematically :  $$\oint \overrightarrow{B}.\overrightarrow{dl} = \mu_{0}I$$ Where , $\overrightarrow{B}$ is the magnetic field , $\overrightarrow{dl}$ is the small element , $\mu_{0}$ is the absolute permeability of free space and I is the current enclosed by the closed path. Proof : Consider an infinitely long straight conductor carrying current I. The magnetic field lines are produced around the conductor as concentric circles. The magnetic field due to this current carrying infinite conductor at a distance a is given by $$B = \frac{\mu_{0}}{4\pi }(\frac{2I}{a})$$                            Consider a circle of radius a around the wire (cal...

Biot-Savart's law is used to determine the strength of the magnetic field at any point due to a current carrying conductor. Consider a very small element AB of length dl of a conductor carrying current I. The strength of magnetic field dB due to this small current element $(I\overrightarrow{dl})$ at point P, distant r from the element is found to depend upon the quantities as under: $$(i) dB \propto dl$$ $$(ii) dB \propto I$$ $$(iii) dB \propto sin\theta$$  where $\theta$ is the angle between $\overrightarrow{dl}$ and $\overrightarrow{r}$. $$(iv) dB \propto \frac{1}{r^{2}}$$ Combining (i) to (iv) , we get  $$dB \propto \frac{Idlsin\theta}{r^{2}}$$ $$dB = k \frac{Idl sin\theta}{r^{2}}$$ Where k is a constant of proportionality. In S.I units, $$k = \frac{\mu_{0}}{4\pi}$$ where , $\mu_{0}$ is called absoulte permeability of free space i.e . vacuum. Hence , equ (i) becomes  $$dB = \frac{\mu_{0}}{4\pi}. \frac{Idlsin\theta}{r^{2}}$$ Value of $\mu_{0}$ in S.I units = $4\pi \time...

  Chapter–4: Moving Charges and Magnetism: Concept of magnetic field,  Oersted's experiment to show magnetic effects of electric current & Ampere's swimming Rule Magnetic Field and Magnetic Force State and Explain Lorentz Force   Force on a current-carrying conductor in a uniform magnetic field . Motion in a magnetic field  Magnetic field due to current element :  Biot - Savart law  Magnetic field on the Axis of a circular current loop.  Ampere's law - Proof   its applications to infinitely long straight wire.   Force between two parallel current-carrying conductors. Force between two parallel current-carrying conductors. definition of ampere,  torque experienced by a current loop in uniform magnetic field. Current loop as a magnetic dipole and its magnetic dipole moment ,  Moving coil galvanometer its principle , theory and construction . current and voltage sensitivity of galvanometer.  What is ammeter ? conversion G...

Force between two infinitely long straight parallel conductors carrying currents -  ( i ) two infinitely long straight parallel conductors carrying currents in the same direction :  Consider two infinitely long parallel conductors X and Y carrying current $I_{1}$ and $I_{2}$ respectively in the same direction . let d be the distance of separation between these two conductor. The current $I_{1}$ in the conductor X produces a magnetic field around it. The magnitude of magnetic field at any point on the conductor Y due to current carrying in the conductor X is given by :  $$B_{1} = \frac{\mu_{0}}{4\pi} (\frac{2I_{1}}{d})$$ The direction of  $\overrightarrow{B}_{1}$  is perpendicular to the plane of the conductor Y and is directed into the plane as per right hand thumb rule , We know a current carrying conductor of length l placed as right angle to the magnetic field (B) experience a force is given by :  $$F =BIl$$ Therefore force experience per unit length of ...

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NCERT Notes for Class 10 Science Physics Chapter 11 Electricity   is prepared and uploaded for reference by a team of expert members of Param Himalaya. Get  NCERT Exercise Solution Class 10 Science Chapter 11 Electricity. Electricity :  Electricity is a controllable and convenient form of energy and defined as the flow of electric charge.   Electric Charge  :  Electric charge can be defined as a fundamental property of subatomic particles that gives rise to the phenomenon of experiencing force in the presence of electric and magnetic fields. Some  properties of electric charge 1.  Electric charges are of two types - Positive charges or protons have a charge of $+1.6 × 10^{-19}$ Coulomb. Negative charges or Electrons have a charge of $-1.6 × 10^{-19}$ Coulomb. 2. Charge is a scalar quantity. 3. Charge is transferable, Charge( Electron) transfer from one body to another. 4. Like charges repel each other and unlike. charges attract each other. 4...