Chapter three eddy current

Question 1

diff eddy current

Answer 1

it is induced current generated in metalic cores if the magnetic flux through changes , which flow in closed flow in closed (EDDY) paths perpendculer to the magnetic flux lines

Question 2

How to make variation in magnetic linked with a metalic core

Answer 2

1. move the metalic core in suitaple magnetic filed
2. subject the metalic core to variable magnetic filed like that of AC current

Question 3

eddy current may have bad or useful effects GR

Answer 3

• bad effects ;

in some electric divises contain metalic core subject to variable magnetic of AC like transformer [mopile charges]

1. it causes loss in the electric energy as thermal energy
2. it leads to rise in temperature that may cause melting and damage

• useful effect
  1. it may be used to melt metals in induction furnaces

Question 4

what is the precaution to minmize bad effects of eddy current

Answer 4

1. metalllic core should be divided into thin insolated sheets
2. metalic cores should have high resistance to minmize the eddy current SO ;

• they may be made of siliconic soft iron of high resistavity
• the sheets must be very thin R & 1\A

Question 5

what is the appliction on eddy current

Answer 5

induction furnaces

Question 6

what is the use of induction furnaces and idea of operation

Answer 6

1. uses to melt metals
2. generating eddy current in metallic blocks by subjecting it to variable magnetic flux like that of the alternating current ( AC )

Question 7

it is recommended to use alternating current with very high frequency

Answer 7

AC has variable magnetic flux , and increasing the ferquency will increases the rate of change of the magnetic flux that link with the metallic blocks so the induced E.M.F will increases according to faradays law ( E_ind & Dø_m \ Dt ) and also the eddy current will increases [I_ind & E_ind \ R] causing more thermal effect