Answer / nagendra murthy

any DC motor or generator will need to have a commutator. A
commutator is a device used to change the direction of
current flow through the motor. The reason a cummutator is
needed is because a DC current in a magnetic field can only
turn the motor through 180 degrees, after which the force
will cause the motor to return to a fixed position. In order
to make the force turn the motor the current needs to be
changed every 180 degrees so that the force will act in the
opposite direction, spinning the motor around. This is
achieved using a commutator. The commutator is normally a
device which brushes against terminals in the motor. As the
motor turns the terminals in contact with the brushes
change, and so does the current.

Answer / paragbajpai

1.carbon brushes are used as it is having high resistance so
that time constant will be reduced that means commutation
will be improved.
2. it has self relieving property

Answer / k.prakashchandra

1.A good conductor 2.has desired hardness 3 can be easily
Reshaped 4.cheap 5. easily available 5. does not corrode 6.
cleaning is easy 7.weather resistant 8 not inflammable etc

Answer / sarath k

the carbon brushes are used as commutators because of resistance commutation and the carbon has self polishing property

Answer / satheeshkumar

Only The carbon having possessing the negative temperature coefficient This is the main reason using for commutation porpose (The ratio of increasing resistance per degree centigrade o the resistance at 0 degree centigrade) dippend the carbon inverse action must take place

Answer / gautam

carbon acha nahin hota hai

WHAT IS SYNCHRONISING?

8 Answers   L&T,

what is magnetizing and demagnetizing current in generator and motor?

0 Answers   HBL Power Systems,

what difference between thermal and bi-metal over load relay?

2 Answers  

operation of protection relay watchdog contact?

0 Answers   L&T,

what is the difference between squirrel cage & slip ring induction motor by construction & working principle ?

1 Answers   Sail,

we the the value of frequency is 50 HZ in DG then why we said the value inductive rectance is zero in DG?

1 Answers  

What is sinusodial & non sinsodial current

1 Answers  

CAN WE GENERATE AC WITHOUT DC EXCITATION?

1 Answers  

what is the standard values(Megger test) of resistances between L&N,L&E and N&E for a system on IEE regulations?

0 Answers  

Please tell me if you are electrical engineer,and you are appointed for the maintainance of Electrical Power plant,then which parts of the plant deal with you.Also tell how these parts/components work.

1 Answers  

Why we use shunt coil in breaker??????????

7 Answers  

why is the rating of transformer done in kva and not in kw.

21 Answers   Honeywell, Satyam,