A dipole of moment 0.50 a middot nm is placed In a uniform electric field with a

Question

A dipole of moment 0.50 a middot nm is placed In a uniform electric field with a magnitude of 7.0 times 10^4 N/C. What is the magnitude of the torque on the dipole for each of the following situations? the dipole is aligned with the electric field the dipole is traverse to (perpendicular to) the electric field the dipole makes an angle of 32.5 degree with the direction of the electric field Defining the potential energy to be zero when the dipole Is transverse to the electric field, find the potential energy of the dipole In the electric field for the orientations specified in Parts (a) and (c)

Explanation / Answer

formula for torque is

T = pE sin theta

(a)

theta = 0

T = 0.50e. nm ( 7 * 10^4) sin 0 = 0

(b)

theta = 90

T = 0.50e. nm ( 7 * 10^4) sin 90

=0.5 ( 1.6 * 10^-19) ( 10^-9 m) ( 7 * 10^4) 1

=5.6 * 10^-24 N m

(c)

T = 0.50e. nm ( 7 * 10^4) sin 32.5

=0.5 ( 1.6 * 10^-19) ( 10^-9 m) ( 7 * 10^4) 0.537

=3.0 * 10^-24 N m

(d)

formula for potential energy

U = -pE cos theta

when theta = 0

U = -pE cos theta

=-0.5 ( 1.6 * 10^-19) ( 10^-9 m) ( 7 * 10^4) cos 0

=-5.6 * 10^-24 J

when theta = 32.5

U = -pE cos theta

=-0.5 ( 1.6 * 10^-19) ( 10^-9 m) ( 7 * 10^4) cos 32.5

=-4.72 * 10^-24 J

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