1.

A conducting bar of 3m length is allowed to fall freely from 80m high tower, keeping it aligned along the East-West direction. Find the emf induced in the rod when it is 20m below the top of tower. g=10 ms^(-2) , B_h=0.7xx10^(-4)T and angle of deep = 60^@ .

Answer»

2.5 mV
2.1 mV
2.7 mV
1.2 mV

Solution :Here l=3 m
h=80 m
d=20 m
`g=10 ms^(-2)`
`B_h=0.7xx10^(-4)`T
`phi=60^@`
Put `v_0=0` in kinetic equation `V^2-v_0^2=2gd`
`therefore v^2=2gd`
`therefore v^2=2xx10xx20`
`therefore v^2=400`
`therefore` v=20 m/s
`rArr` Kinetic EMF
E=Bvl
`=B_h COS phi vl`
`=0.7xx10^(-4) XX cos60^@xx20xx3`
`=0.7xx10^(-4)xx1/2xx20xx3`
`=2.1xx10^(-3)` V
`therefore` E=2.1 mV


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