A parallel plate capacitor of 3mF is fully charged up using a 20V battery. The b
ID: 2101255 • Letter: A
Question
A parallel plate capacitor of 3mF is fully charged up using a 20V battery. The
battery is disconnected when the capacitor is fully charged.
A.When the battery is disconnected, a material with dielectric constant K=2
is inserted between the parallel plates. Which of the following is false?
a) The potential between the plates remains constant
b) The charge on the plates remains constant
c) The electric field between the plates is decreased
d) An electric field is induced in the dielectric material
e) The capacitance of the system increases
B.What is the new capacitance after the dielectric material is fully inserted?
C.What is the new potential difference between the plates?
D.Which of the following is true about the energy density contained in an
electric field, E?
a) It is proportional to the inverse of the permittivity of the region where we
measure the electric field, 1/?
b) An electric field has no associated energy density
c) It is proportional to the square of the strength of the electric field, E2
d) It doesn
Explanation / Answer
A). a is false;;;;;;;; B). C(new) = K*C(old) = 2*3 =6mF;;;;;;;;;; C). Q =C.V = 3*20 =60 mV;;;;; V = Q/C =60/6 =10V ;;;;;;;;; D). e is correct.