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1) A dipole with dipole moment 1.5 nC*m is oriented at 30 degrees to an electric

ID: 2012882 • Letter: 1

Question

1) A dipole with dipole moment 1.5 nC*m is oriented at 30 degrees to an electric field, 4.0*10^6 N/C. (a) What is the torque on the dipole? (b) How much work is required to rotate the dipole until it is parallel to the field (hint: think about work-energy relationship)?

(2) Two parallel-plate capacitors with different plate separation but the same capacitance are connected in series to a battery. Both capacitors are filled with air. The quantity that is NOT the same for both capacitors when they are fully charged is (please explain):
    (A) potential difference
    (B) stored energy
    (C) electric field between the plates
    (D) charge on the positive plate
    (E) dielectric constant

(3) 20 loops of wire with a radius of 7.5 cm rotates about a diameter in a uniform magnetic field of 1.6 T. To produce a maximum emf of 20.0 V, it should rotate at:
   (A) 0
   (B) 2.7 rad/s
(C) 5.6 rad/s
   (D) 35 rad/s
   (E) 71 rad/s

Explanation / Answer

Electric Dipole moment P = 1.5 nC m                                        = 1.5*10^-9 C m Electric field E = 4*10^6 N/C Angle between dipolemoment P and Electric field E, = 300 (a) Torque acting on the Dipole, = P X E                                               = PE sin                                               = (1.5*10^-9 C m)(4*10^6 N/C) sin30                                                  = 3*10^-3 N m (b) Work done W = PE cos                        = (1.5*10^-9 C m)(4*10^6 N/C) cos30                        = 5.2*10^-3 J Please post the other questions seperately.Our rules not allowed us to answer more than one question in one post.Thank you so much.    (a) Torque acting on the Dipole, = P X E                                               = PE sin                                               = (1.5*10^-9 C m)(4*10^6 N/C) sin30                                                  = 3*10^-3 N m (b) Work done W = PE cos                        = (1.5*10^-9 C m)(4*10^6 N/C) cos30                        = 5.2*10^-3 J Please post the other questions seperately.Our rules not allowed us to answer more than one question in one post.Thank you so much.