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A molecule of a substance has permanent ...

A molecule of a substance has permanent dipole moment p. A mole of this substance is polarised by applying a strong electrostatic field E. The direction of the field a suddenly changed by an angle of `60^(@)`. If N is the Avogadro's number the amount of work done by the field is

A

2NpE

B

`(1)/(2)NpE`

C

NpE

D

`(3)/(2) NpE`

Text Solution

Verified by Experts

The correct Answer is:
B
Work done by the field for a dipole
`W= P E [cos theta_(1)- cos theta_(2)]`
`theta_(1)= 0 theta_(2)= 60`
`W= P E [cos 0- cos 60]`
`W= (P E)/(2)`
for ..N.. molecule
`W= (N P E)/(2)`
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