1 ) The electric current in a circular coil of two turns produced a magnetic induction of 0.2 T at its center . The coil is unwounded and then rewounded into circular coil of four turns . If same current flows in the coil , the magnetic induction at the center of coil now is : -
A ) 0.1 T , B
) 0.8 T ,
C ) 2.9 T , D
) None of these ,
Correct
Answer : - B ) 0.8 T ,
Solution : -
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2 )
An electron moves at right angle to magnetic field of 1.5 x 10^(-2) tesla with
a speed of 6 x 10^7 m / s . If the specific charge of electron is 17 coulomb /
kg , the radius of circular path will be : -
A ) 1.5 cm , B
) 2.35 cm ,
C ) 3.91 cm , D ) None of these ,
Correct
Answer : - B ) 2.35 cm ,
Solution
: -
For a charge particle moving perpendicular to the field .
Radius
: - r
= mv / Bq .
Specific charge
= q / m = 1.7
x 10 ^ 11 C / kg .
So , r
= ( 6 x 10 ^ 7 ) / (
1.7 x 10^11 x 1.5 x 10^(-2) ) ,
r = 2.35 x 10 ^ ( -2 ) m ,
So , r = 2.35 cm , Answer .
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