Home
Class 12
PHYSICS
A molecule of a substance has a perman...

A molecule of a substance has a permanent electric dipole moment of magnitude `10^(-29) `C m. A mole of this substance is polarized at low temperature by appling a strong elecrostatic field of magnitude `10^(6) V m^(-1)`. The direction of the field is suddenly changed by an angle of `60^(@)`. Estimate the heat released by the substance in aligning its dipole along the new direction of the field. For simplicity, assume `100%` polarisation of sample.

Text Solution

Verified by Experts

Here, dipole moment of each molecule ` = 10 ^(-29)` C . As 1 mole of the substance contains `6 x 10^(23)` moelcules, total diople momemt of all the molecules .
` P = 6 xx 10^(23) xx 10^(-29) Cm = 6 xx 10^(-6) Cm`
Initial potenital energy ,
`U_(i) = - pEcos theta = - 6 xx 10^(-6) xx 10^(-6) cos 60^(@) = - 3J`
Final potential energy (when `theta = 60^(@)`)
`U_(f) = 6 xx 10^(-6) xx 10^(6) cos 60^(@) = - 3J`
Change in potential energy = - 3J - (-6J) = 3J
So ,there is loss is potential energy . This must be the energy released by the substance in the form of heat in aligning its dipoles .
Promotional Banner

Topper's Solved these Questions

  • ELECTROSTATIC POTENTIAL AND CAPACITANCE

    NARAYNA|Exercise Evaluate yourself-1|5 Videos

  • ELECTROSTATIC POTENTIAL AND CAPACITANCE

    NARAYNA|Exercise Evaluate yourself-2|8 Videos

  • ELECTROMAGNETIC WAVES

    NARAYNA|Exercise EXERCISE -4|15 Videos

  • ELECTROSTATICS AND GAUSS LAW

    NARAYNA|Exercise Intergers type question|11 Videos

Similar Questions

Explore conceptually related problems

An electrtic dipole with dipole moment 4xx10^(-9) C m is aligned at 30^(@) with the direction of a uniform electric field of magnitude 5xx10^(4) NC^(-1) . Calculate the magnitude of the torque acting on the dipole .

The amplitude of the electric field of a plane electromagnetic wave in air is 6.0 xx 10 ^(-4) V m ^(-1). The amplitude of the magnetic field will be

The electric field at a point on equatorial of a dipole and direction of the dipole moment

A neutral water molecule (H_(2)O) in its vapor state has an electric dipole moment of magnitude 6.2xx10^(-30)C*m . If the molecule is placed in a electric field of 1.5xx10^(4)N//C , what maximum torque can the field exert on it? (Such a field can easily be set up in the laboratory.)

The work in rotating electric dipole of dipole moment p in an electric field E through an angle theta from the direction of electric field, is:

An electric dipole has the magnitude of its charge as q and its dipole moment is p . It is placed in a uniform electric field E . If its dipole moment is along the direction of the field, the force on it and its potential energy are respectively