The circuit in fig. consists of wires at the top and bottom and identical metal springs at the left and right sides.The wire at the bottom has a mass of 10.0g and is 5.00cm long. The wire is hanging as shown in the figure. The springes stretch 0.500 cm under the weight of the wire, and the circuit has a total resistance of `12.0Omega`. When a magnetic field is turned on the springes stretch an additional 0.300 cm.

From the above statements we can conclude that

Options

A. the magnetic field is directed into the plane of page
B. the magnetic field is directed out of the page
C. The magnetic field is toward left in the plane of page
D. The magnetic field is toward right in the plane of page

Answer

b

Explanation

`I=epsilon/R=24/12=2A` M

`Magnetic force =IlB sin (pi/2)=2xx5xx10^-2xxB=B/10`
`2kx_1=mg, 2k=(mg)/(x_1) ` and
`2k(x_1+x_2)=mg+IlB`
`2kx_1+2kx_2=mg+IlB`
`(mg)/(x_1) x_2=IlB`
`10xx10^-3xx10xx0.3/0.5=B/10 implies B=600xx10^-3=0.6T`