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

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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...
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Electromagnetic Waves | radiation | physics

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Electromagnetic waves :-


An electromagnetic wave is one in  which electric and magnetic field mutually perpendicular to each other as well as the direction of propagation of the wave.

An accelerated charge produces a sinusoidal time varying magnetic field, which in turm produces a sinusoidal time electric field. The two fields so produced are mutually perpendicular and are source of each  other. The mutually perpendicular time using electric field and magnetic field constitute a electromagnetic waves which propagate in space in direction perpendicular to the direction of both the fields.

Thus the electromagnetic waves consist of sinusoidal time varying electric and -ve field acting at right angle to each other as well as at right angle to the direction of propagation of waves as shown in figure.


• Characterstics of electromagnetic waves :-


1. The electromagnetic waves are produced by an accelerated charge. 

2.At any point in vacuum, the electric field vectors and magnetic field vectors are mutually perpendicular to each other. 

3. These waves are transverse in nature i.e the electric field and magnetic field are  perpendicular to the direction of propagation of waves. 

4. As the waves spread outward into free space, the amplitude of electric field and magnetic field decreases steadity .

5. The electromagnetic waves obey the principal of superposition, i.e when two or more disturbance are superimposed the resultant field vector is sum of individuals field vectors. 

6. Electromagnetic waves do not require material medium for their propagation. 

7. Electromagnetic waves travel with velocity of light. 

8.The energy in electromagnetic waves is devided equally between the electric field and magnetic field. 

9. The electromagnetic waves many different frequency can exist. 

10. The electric vector is responsible for optically effect due to an electromagnetic wave. For this reason, electric vector is called light vectors .


•Properties and application of electromagnetic waves :- 




•Some important board exam level question answers :-


Q. 1) Write four uses of Gama rays? 

Ans:- 1.They are used in treatment of cancer. 
2.They are used in destroying Bacteria. 
3.They are used for food preservation. 
4.They are used in Nuclear reactions. 


Q. 2) Write four uses of X Rays? 

Ans:- 1.They are used in detection  of born fracture.  
2.They are used in detection cracks in metal plates . 
3.They are used treatment of skin decease 
4.They are used in study of crystal structures. 


Q. 3 What are electromagnetic waves  ?

Ans:- An electromagnetic wave is one in  which electric and magnetic field mutually perpendicular to each other as well as the direction of propagation of the wave.







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Physics

Electric lines of force (electrostatic) | electostatic | physics

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

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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...
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Electric field (electrostatic) | electostatic | physics

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

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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...
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