3. A)
Two point charges, -50 uC and +25 C, are separated by a distance of 15 cm as
shown in the figure. If a proton of charge 1.6 x 10-C is gently placed at point P, 5
cm from charge Q2, then determine the net electric force (magnitude and direction)
experienced by the proton
15 cm
[4]
х

-50 με
25 uc
Р
B)
Two conducting square plates 6.5 cm on a side and separated by 2.3 mm air gap
(dielectric constant of air gap is assumed to be 1) is fully charged with a 12.0 V
battery. The battery is then disconnected and a dielectric material of dielectric
constant 2.3 is inserted.
[6]
a)
b)
Determine the charge stored in each plate.
Determine the capacitance of the plates when dielectric material was inserted.
Determine the potential difference between the plates when battery was
disconnected and dielectric material was inserted.
c