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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Alternating current generator AC | physics

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Alternating current generator   (Electromagnetic induction and current) :-


The device which converts mechanical energy into electrical energy is called alternating current generator. 

• Principal :- 


When magnetic flux linked with a coil changes, an induced e m f is produced across it. 

• Construction :-


It is consist of following four parts. 

1.Armature :- 

Armature ABCD ( also called coil)  consist of a large number of turns of insulate copper wire around over a soft iron core. It revolves round an axle between the two poles of a strong magnet .


2. field Magnet :- 

It is usually a strong permanent magnet. The armature is rotated between the two poles of a strong magnet so that axis of the armature is perpendicular to magnetic field lines .

3. Slip rings :---

The leads from the arms of the armature are connected to the two rings R1 and R2 
Respectively. These rings help to provide movable contact and for this reason, they are called hency the leads rotates about the central. 

4. Brushes's :- 

The flexible metallic pieces carbon pieces B1 and B2 called  brushes are used to pass on The current from rings to the external load resistances R.  As the slip rings rotates the brushes provide movable contact by keeping themselves pressed against the rings. 


•Working :-


Let us suppose that the armature is rotated insuch a way of arm AB moves in upward and arms moves in down wards. Then applying Flemings right hand rule, we see that current flows in armature .


After the armature has rotated the 180° ,it occupied the position as shown in figure. 

We see that the direction of current changes in the external circuits after every half revolution of the armature i.e after the armature has rotated through an angel 180° from its initial position. Hence current thus produced is alternating in nature. 







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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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