A bar magnet makes 40 oscillations per minute in an oscillation magnetometer. An identical magnet is demagnetized completely and is placed over the magnet in the magnetometer. Find the time taken for 40 oscillations by this combination. Neglect any induced magnetism.

Explanation

`T= 2 pi sqrt((1)/(BM_(H)))`
`T_(1) = (1)/(40) min , T_(2) = ?`
` (T_(1))/(T_(2)) = (i)(l)`
`rArr (1)/(40T_(2)) = sqrt(1)/(2))`
(From question)
` (1)/(1600T_(2)^(2)) = (1)/(2)`
`rArr T_(2)^(2) = (1)/(800)`
`rArr T_(2) = 0.03536 min`
For 1 cecillation time taken
`0.03536 min`
For `40` oscillition time
`0.03536 xx 40`
`= 1.414 min = sqrt(2) min `