The Science

Eddy currents:-        The current induced in a conductor (metal sheet or metal block)  in form of clesed loops .these loops are called eddy currents because these currents look like Eddies or which pods. These current are also known as focarlt current.  Experiments :-   https://instagram.com/sachin_dreamboy?igshid=1647004f4d5r6 Explanation :- When the circuit is suritered  in, the current shorts growing through the solenoid. As the current grows, the magnetic field lines along the axis of the solenoid and hence the magnetic flux through the dix also increases from zero yo some finite value. Due to this, induced current are produced in the disc and the disc is converted into a small magnet. If the upper face of the soft iron core acquires N polarity in accordance with lenz's lawer face of the disc acquires N polarity due to repulsion face between the upper face of the soft iron core and the lower face of the disc ,the disc is throw...

History of Lenz's Law:- Faraday could only tell ,when and how much induced emf is produced. It was the Russian scientist H. F. E lenz who gave us in 1833 the direction of the induced emf. His experiments are known as lenz law.  Explanation :- Connect a galvanometer to coil. Take a magnet NS and move into the coil with it's north pole downlwords. The deflection in the galvanometer is towards left which indicates that the current in the coil flows in anticlockwise direction as seen from above. Hence upper force of the coil has acquired north polarity due to flow of induced current through it.  If we move the magnet out of the coil ,the deflection us towards right, indicates that the current is upper face of the coil flows in clockwise direction as seen from above, hence upper face of the coil has aquired north polarity due to flow if induced current through it.  Similarly, if the magnet is moved into or out of the coil with its aouth pole downward ...

The results of Faraday's Experiments on electromagnetic interaction are known as faraday's law  of electromagnetic induction.  1.Faraday's First law of electromagnetic induction :- Whenever magnetic flux linked with a circuit changes, induced EMF is produced. The induced emf losts as long as change in magnetic flux continue.  2. Faraday's second Law of electomagnetic Induction :- The magnitude of the emf is directly proportional to the rate of change of the magnetic flux linked with circuit.                MATHEMATICALLY                 ε  ∝ dΦ/dt                                 ε= - kdΦ/dt  Here - k is constant of proportionality .In SI k=1 ,-ve sign indicates that the induced emf gas got opposing nature ie direction of flow of current due to induced emf is such that i...

•Electromagnetic induction :- The phenomenon of production of electric current in a coil, when the magnetic flux linked with the coil is changed is called electromagnetic induction.  •Magnetic flux :- Magnetic flux is a measure of number magnetic field lines passing through same surfaces.  It is a scalar quantity. It is denoted by  Φ. •Unit of magnetic flux :- SI unit of magnetic flux is weber (wb).    For normal field to surface                Φ=BS When B=1T            S=1m² Then               Φ=1T m²              =1weber.  •Weber:- The magnetic flux with a surface are of 1 m² held normally in a magnetic field of 1T is called one weber.      Cgs unit of Φ is maxwell(Mx).                Φ=BS If B=1 gauss ...

1.Diamagnetic substances :- The substances which are feebly magnetised in a direction opposite to that of the magnetising field when placed in it are called diamagnetic substances.  Examples:- Bismith, Antimony, copper, gold, murcury, water, alcohol, air, hydrogen, etc are called diamagnetic substances.  2.Paramagnetic substances :- The substances which are feebly magnetised in direction of the magnetising field when placed in it are called paramagnetic substances.  Example :- Aluminum, platinum, chromium, manganese, copper sulphate, Crown glass etc are some of paramagnetic substances 3. Ferromagnetic substances :- The substance which are strongly magnetised in the direction of magnetising field in which they are placed are called ferromagnetic substances.  Examples:- Iron, cobalt, nickle and a few of alloys

Biat savart's law:- According to the Biot-Savart law, magnetic field dB due to current element dl, at a point P situated at distancer from the current element Idl is: i) directly proportional to the current element Idl.   ii) directly proportional to the sine of the angle (θ) between current element and r,  iii) inversely proportional to the square of the distance r between current element and the point dB∝Idl (sinθ)/r2 dB = (μo/4π)×Idl×(sinθ)/r2 dB = Idl × r / r3

What is magnetism?  The property of a substance to attracting small pieces of iron, steel and some other substances is called magnetism.  Magnet:- The substance which exhibits property of attracting small pieces of iron, steel and some other substances is called magnet. Natural magnet:- The minerals which exhibits property of magnetism are called natural magnets.  Artificial magnets :- Man made magnets convenient for practical purposes are called artificial magnets.  Magnetic poles:- The regions near ends of a magnet where the property of attraction is most prominent are called magnetic poles. Axis  of magnet:- A line joining the poles of a magnet is called axos of the magnet  Magnetic length :- The distance between the true position of length of north and South poles is called magnetic length (NS)  Geometric length :- Length  of a magnet is called it's geometric length. Magnetic dipole and mag...

•Kirchoff's First law (kcl):- It states that the algebraic sum of current meeting or leaving a point is always zero. It is also called functional rule. •Example:- Consider a point N in an electric circuits in which current I1, I2, I3, i4 and I5 passing through resistances. Applying Kirchhoff's law I1+I2-I3+I4-I5=0 •Kirchoff's second Law (kvl) :- In a loop the algebraic sum of the emf's is equal to the algebraic sum of products of the resistance and the respective current passing through it. It is also called kirchoff's voltage law.  •Example :- •Some important board exam level question answers :- Q. 1) Write Kirchhoff's First law  ? Ans:-  It states that the algebraic sum of current meeting or leaving a point is always zero. It is also called functional rule. Q. 2) Write Kirchhoff's second Law  ? Ans:-  In a loop the algebraic sum of the emf's is equal to the algebraic sum of products of the resis...

Capacitor and It's Expression (Electrostatics)   What is capacitor?  An arrangement for storing large amount of electric charge in small space is called capacitor.  Principal of capacitor :- A capacitor works on the principal, "The capacity of an insulated charged conductor is increased appreciate by bringing near it an earth connected, unchanged  conductor Definition of capacitance :- Capacitance of a conductor may be defined as the ratio of the electric charge on it to it's electric potential due to that charge                              C=Q/V Expression for parallel plate capacitor :- Let the two plates are kept parallel to each other separated be a distance d and cross-sectional area of each plate is A.   We konw that,                     C= Q/V According to the gauss law, the electric fie...

Conductors, insulators and Dielectrics  (Electrostatic)   • What is conductor ? Conductors are the Materials or substances which allow electricity to flow through them. They conduct electricity because they allow electrons to flow easily inside them from atom to atom. Also, conductors allow the transmission of heat or light from one source to another. Metals,humans, earth,  and animals are all conductors. This is the reason we get electric shocks! Moreover, the human body is a good conductor. So it provides a resistance-free path for the current to flow from wire to body. Conductors have free electrons on its surface which allow current to pass through easily. This is the reason why conductors are able to conduct electricity . Example :- • Material such as silver is the best conductor of electricity. But, it is costly and so, we don’t use silver in industries and transmission of electricity. • Copper, Brass, Steel, Gold, and Alumini...

  Electric Flux (Electrostatics)     Introduction :- Electric Flux is defined as a number of electric field lines, passing per unit area. It is another physical quantity to measure the strength of electric field and frame the basics of electrostatics. It is also defined as the product of electric field and surface area projected in a direction perpendicular to the electric field. Let’s understand what the term flux actually means, with an example:-      Suppose there a liquid flowing with velocity ‘v’, through tiny surface dS, in a normal direction with respect to the surface. The rate of flow of water will be volume passing through the area per unit time that is v dS. Volume = Area × Length Differentiating the above relation with respect to time, we get d Volume/ dt = dS × d length/ dt Flow of liquid = dS × v where dS is a surface area perpen • Some Important board exam level question answers :- Q. 1) Define electric f...

Gauss’s Theorem (Electrostatic)   Statement:- According to Gauss’s theorem the net-outward normal electric flux through any closed surface of any shape is equivalent to 1/ε0 times the total amount of charge contained within that surface. Proof of Gauss’s Theorem Statement:- Let the charge be = q Let us construct the Gaussian sphere of radius = r Now, Consider , A surface or area ds having ds (vector) Normal having the flux at ds: d e = E (vector) d s (vector) cos θ But , θ = 0 Therefore, Total flux: C = f d Φ E 4 π r2 Therefore, σ = 1 / 4πɛo q / r2 × 4π r2 σ = q / ɛo • Some important board exam level question answers:- Q. 1) Write Gauss's theorem for a charge outside a closed surface.  Ans:- The theorem becomes zero.  Q. 2) What is an equipotential surface ? Ans:- A surface, which has same electric   potential everywhere on it is called   equipotential surface.  Ask me qu...

•  Electric potential (Electrostatics) An electric potential is the amount of work needed to move a unit of charge from a reference point to a specific point inside the field without producing an acceleration. Typically, the reference point is the Earth or a point at infinity, although any point can be used.                  Other units: statvolt SI unit:  volt In SI base units:  V = kg⋅m 2 ⋅A −1 ⋅s −3 Common symbols:  V Dimension:  M L 2  T −3  I −1 Formula V = electric potential k = Coulomb constant q = charge r = distance of separation Volt :---    The electric potential at a point is said to be one volt, if one joule of work is done in moving a charge of one coulomb from infinity to that point against electrostatic force due to electric field.  • Some  Board  Exam ...

•Electric Dipole  (Electrostatics) A system of two equal and opposite charges separated by certain distance is called electric dipole. Change -q and +q at Points A and B separated by distance of 2a=AB constitute an electric dipole.            Electric Dipole Moment  Electric dipole moment of an electric dipole is a vector direction from -ve charge to +ve charge and having magnitude equal to product of magnitude of either charge and distance between them.  Direction of electric dipole moment is from -q  to +q . •Some Boards exam level Question Answers:-- Q. 1) What is the SI units of electric dipole moment?  Ans:- The SI units of electric dipole moment are Cm² (Coulomb meter²) . Q. 2) What happens when the electric dipole is held in a non uniform electric field ? Ans:- Some net force and torque do act on the dipole When the dipole sets itself parallel to the field torque becomes Zero, but ne...

Electric field (Electrostatics)  . The space around a charge in which any other charge is acted upon by an electrostatic force is called electric field of charge .                   E = F/q.                  We know that,           F = k Qq. / r 2            Therefore                 E = k Qq. / r 2 *1/q.                      E =kQ/ r 2   The charge "Q" due to which electric field is set up is called source charge and the other charge "q." which experience electrostatic force in the electric field is called test charge . Electric field intensity :- The electric field intensity or electric field strength at a point due to a source charge may be defined as the electrostatic force per unit positive charge a...