الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

Capacitors and capacitance
c
4F u
6F u
Ab
c
c
c c c
a
8F u
2F u
24uF
Figure 6.21
6.18) A parallel plate capacitor is
constructed using a dielectric
material whose dielectric constant
is 3 an whose dielectric strength is
2×10 8 V/m The desired capacitance
is 0.25µF, and the capacitor must
withstand a maximum potential
difference of 4000V. Find the
maximum area of the capacitor
plate.
6.19) In figure 6.19(b) find (a) the
charge, (b) the potential difference,
(c) the stored energy for each
capacitor. With V=100V.
6.20) (a) Figure 6.22 shows a
network of capacitors between the
terminals a and b. Reduce this
network to a single equivalent
capacitor. (b) Determine the charge
on the 4µF and 8µF capacitors
when the capacitors are fully
charged by a 12V battery
connected to the terminals. (c)
Determine the potential difference
across each capacitor.
Figure 6.22
6.21) A uniform electric field
E=3000V/m exists within a certain
region. What volume of space
would contain an energy equal to
10 -7 J? Express your answer in
cubic meters and in litters.
6.22) A capacitor is constructed from
two square metal plates of side
length L and separated by a
distance d (Figure 6.23). One half
of the space between the plates (top
to bottom) is filled with
polystyrene (κ=2.56), and the other
half is filled with neoprene rubber
(κ=6.7). Calculate the capacitance
of the device, taking L=2cm and
d=0.75mm. (Hint: The capacitor
can be considered as two capacitors
connected in parallel.)
L
Dd
K= 2.56
K= 6.7
Figure 6.23
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