SSC JE Electrical Engineering 2012 Paper

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Question : 186 of 200

Marks: +1, -0

If the length of a bar of magnetic material is increased by 20% and the cross-sectional area is decreased by 20%, then the reluctance is

Increased by 50%
Remaining same
Decreased by 33%
Increased by 67%

Solution:

Reluctance R

=l/{µ_0µ_rA}

R_1/R_2=l_1/l_2.(r_2/r_1)^2=1/1.2 (1.2/1)^2

= 1.2

R_1= 1.2R_2

Increased by 50%.

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