Answer:A
Explanation:
In R-L circuit current is given by
![i=i_0\left [ 1-e^{\frac{-t}{L/R}}\right ]](https://tex.z-dn.net/?f=i%3Di_0%5Cleft%20%5B%201-e%5E%7B%5Cfrac%7B-t%7D%7BL%2FR%7D%7D%5Cright%20%5D)
where i=current at any time t
R=resistance
L=Inductance
at t=0 
approaches to 1
therefore ![i=i_0\left [ 1-1\right ]](https://tex.z-dn.net/?f=i%3Di_0%5Cleft%20%5B%201-1%5Cright%20%5D)
i=0
when t approaches to 
, approaches to zero
thus 
thus we can say that initially circuit act as broken wire with zero current
and it increases exponentially with time and act as ordinary connecting wire
Answer
3.340J
Explanation;
Using the relation. Energy stored in capacitor = U = 7.72 J
U =(1/2)CV^2
C =(eo)A/d
C*d=(eo)A=constant
C2d2=C1d1
C2=C1d1/d2
The separation between the plates is 3.30mm . The separation is decreased to 1.45 mm.
Initial separation between the plates =d1= 3.30mm .
Final separation = d2 = 1.45 mm
(A) if the capacitor was disconnected from the potential source before the separation of the plates was changed, charge 'q' remains same
Energy=U =(1/2)q^2/C
U2C2 = U1C1
U2 =U1C1 /C2
U2 =U1d2/d1
Final energy = Uf = initial energy *d2/d1
Final energy = Uf =7.72*1.45/3.30
(A) Final energy = Uf = 3.340J
A scale can be used to measure miligrams,centigrams,grams and small numbers
As you said p=w/t.
but, w=f×s
=500×5=2500j
t=10s
p=w/t
=2500/10=250 watts
