Question

a parallel plate capacitor is charged such that electric field between the plates of capacitor is E. The energy density of capacitor is

1) Q^2/ 2C
2)1/2 CV^2
3)∈0 E^2
4) 1/2 ∈0 E^2

Answer 1

refer the attachment this is the correct answer

Answer 2

Answer:

thanks my answer please

Explanation:

(a)

Power across capacitor is P=VI

P=V

dt

By definition of capacitance, Q=CV

C

Q

dQ

Energy stored is

U=∫Pdt=

2C

Q

2

Electric field inside the capacitor is given by:

E=

ε

o

σ

=

Aε

o

Q

Capacitance C=

d

ε

o

A

Q=

Substituting (ii) in (i),

U=

2C

E

2

C

2

d

2

=

2

E

2

ε

o

Ad

Energy density

Ad

U

=

2

1

ε

o

E

2

(b)

Let charge on the capacitor before connecting be Q.

After connection, each capacitor has a charge Q/2.

Energy stored before connection, U

1

=

2C

Q

2

Energy stored after connection, U

2

=2

2C

(Q/2)

2

=

4C

Q

2

Hence, energy stored in the combination is less than that of the single capacitor.