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

Eddy current | explain and it's applications | physics

-

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 :-

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 thrown up. 

Application of eddy currents :---


1.Dead beat galvanometer :- 

The oscillation of a moving coil galvanometer generally take a long time to die out but by winding it's coil on a matalic frame made of cooper or aluminum, the galvanometer can be made dead beat.


It is because due to production of eddy currents in matallic frame, the coil of the galvanometer comes to rest very soon. 

2.Induction Motors:-                             

                 

A rotating magnetic field is produced by means oftwo single phase currents. A metallic rotor placed inside the rotating magnetic field          

Starts rotating due to large eddy current produced in it. These motors are commonly used in fans. 

3.Induction furnace :-                        

In an induction furnace, very high temperature can be produced by producing large eddy currents .The high frequency eddy current are passed because of the reason that the heating effect of current is proportional to the Square of the frequency of the current. 

4.Diathermy:-

Eddy currents have been used for deep heat treatment called diathermy. 

5.Speedometer:-


In the speedometer of an automobile a small magnet is geared to the main shoft of the vehicle and it rotates according to the speed.
The magnet is mounted in a aluminum drum with the help of the hair spring. When magnet rotates, it produces eddy currents, the drum tries to oppose the motion of the rotating magnets. In turn, the drum experience a torque and gets deflection through certain angle. A pointer attached to tje drum moves over a calibrated scale, which directly indicates the speed of the vehicle. 

6.Energy meters:-


In energyeters,the armature coil carries a metallic aluminium disc which rotates between the poles of a pair of permanent horse shoe magnets. An the armature rotates the current induced in the disc towards to oppose the motion of the armature coil. 
Due to this braking effects, the deflection is proportional to the energy consumed. 

7.Electric brakes :-

A metallic drum is coupled to wheels of the train, so that when the train runs the drum also rotates. In order to stop the traina, a strong magneteic
Field is applied to the rotating drum.The large eddy currents produced oppose the motion of the drum since drum is connected to the wheels of  the train, it comes to a halt. 




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