current | resistivity | Current electricity | ohm law | electric current | physics

-
Image
Current electricity and ohm's law(Current electricity) :- •What is current? Rate of flow of electric charge with time through any cross section of a wire is called current. It is denoted by I . Thus if charge "dq" flows through a wire in small time "dt" then electric current through wire is given by :                                             I=dq/dt  1 ampere = 1coulomb/1 second  1A=C/s •Ampere :-                                                           The current Through a wire is called one ampere if one coulomb charge is flow through Any cross section of wire in one second   •Ohm's law:- Ohm’s principal discovery was that the amount of electric current through a metal conductor...
Post a Comment

Lenz's Law | AC | physics

-

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 deflection in the galvanometer Will towards right and left respective showing thereby that the upper face of the coil is south in first case and or in second case. 

From the above experiments, we infer that the upper Face of the coil always acquired such a polarity so as to oppose the motion of the magnet into or out of coil. In case of figures a and c the magnet mive inwards by making the upper face of the coil aquire polarity same as that of the lower Pole of the magnet. 

In figure b and d the magnet moves outward and the wmf so generated majes the upper face of the coil acquired a polarity which opposes the outward motion of the magnet. This is possible only if upper face acquires south polarisation case of fig. b and the north in the case of fig. d. 

We, therefore conclude that the induced emf has no fixed direction of its own. 

If always acquired such a direction so that it can oppose the aquire producing it. The above conclusion is known as the lenz's Law which state the induced current produced in a circuit always flow in such a direction that it opposes the change or the cause of produces it. 

Comments

Post a Comment

Hi everyone ! If you have any doubt You can ask me anytime

Physics

Electric lines of force (electrostatic) | electostatic | physics

-
Image
 •  Electric lines of force        (Electrostatics)  1. The electric lines of force start from positive charge and end at negative charge.      2.  The lines of forces originate or terminate at a surface is always right angle to that surface. 3. The lines of forces never intersect each other. 4. The electric lines of force do not pass through a conductor. 5.Like charges repel each other wherever unlike charges attracted each other  • Some important Question Answer From Board level Exams:- Q. 1) Why electric field lines of force cannot intersect each other?   Ans:- This is because at the point of intersection, two tangent would have to be drawn to the lines of Force. Therefore would be two directions of electric intensity at the same point, which is not possible.  Q. 2) Write Two properties of electric field lines of force?  Ans:-    1. The lines of forces ...
Read more

current | resistivity | Current electricity | ohm law | electric current | physics

-
Image
Current electricity and ohm's law(Current electricity) :- •What is current? Rate of flow of electric charge with time through any cross section of a wire is called current. It is denoted by I . Thus if charge "dq" flows through a wire in small time "dt" then electric current through wire is given by :                                             I=dq/dt  1 ampere = 1coulomb/1 second  1A=C/s •Ampere :-                                                           The current Through a wire is called one ampere if one coulomb charge is flow through Any cross section of wire in one second   •Ohm's law:- Ohm’s principal discovery was that the amount of electric current through a metal conductor...
Read more

Electric field (electrostatic) | electostatic | physics

-
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...
Read more

State and prove the Gauss's Theorem (electrostatic) | electostatic | physics

-
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...
Read more