2. • Capacitor is a device which is used to store charges
• To deposit charges we have to do some work
• We know that whenever we do work in a electric field it store in the
form of potential energy
• W=P.E
• So if some how we calculate work done we can calculate P.E stored
inside the capacitor
ENERGY STORED IN A CAPACITOR
3. • Derivation for P.E
• As we know that, V =
W
q
• W = V q0
• Before charging the electric potential difference between plates is ZERO and
it finally become V when charge q is deposited on it
• Average V =
0+𝑉
2
• Average V =
1
2
𝑉
• W =
1
2
𝑉q
• P.E =
1
2
𝑉q
ENERGY STORED IN A CAPACITOR
4. • P.E =
1
2
𝑉(CV)
• P.E =
1
2
CV2
• Energy stored in term of electric field
C=
𝑨𝛜 𝟎 𝛜 𝒓
𝒅 V = Ed
P.E =
𝟏
𝟐
(
𝑨𝛜 𝟎 𝛜 𝒓
𝒅
)(Ed)2
P.E =
𝟏
𝟐
𝛜 𝟎 𝛜 𝐫 E2(Ad)
ENERGY STORED IN A CAPACITOR
5. • Energy density
• Energy density =
𝑒𝑛𝑒𝑟𝑔𝑦
𝑣𝑜𝑙𝑢𝑚𝑒
• Energy density =
𝟏
𝟐
𝛜 𝟎 𝛜 𝐫 E2(Ad)
𝐴𝑑
• Energy density =
𝟏
𝟐
𝛜 𝟎 𝛜 𝐫 E2
Mass density =
𝒎𝒂𝒔𝒔
𝒗𝒐𝒍𝒖𝒎𝒆
ENERGY STORED IN A CAPACITOR
6. • Definition
• When a electric material is placed in an electric field the negative and positive
charges of dielectric are slightly displaced. This phenomenon is called
polarization and dielectric is said to be polarized
• Effect
• Voltage decreases and capacitance increases
• Explanation
C =
𝑸
𝑽
ELECTRIC POLARIZATION OF
DIELECTRIC
8. • Definition
• The time during which the capacitor charges to 63% of its maximum value is
called time constant
• formula
• Time constant = RC
If RC is lower the charging
and discharging is rapid
If RC if greater then charging and
discharging is higher
CHARGING AND DISCHARGING
OF CAPACITOR
