Gauss law again

1.plz explain, what is the electric flux through each surface in a cube when a point charge is kept at one corner of the cube. mag of charge is q.

2.

each capacitor has capacitance C , find energy drawn from source
Ans. 3CE2

how??

5 Answers

106
Asish Mahapatra ·

Q1. When a charge is kept in a corner of a cube. Imagine there are 8 such cubes (as in the corner atoms of a simple cubic cell) So now the given charge is symmetrically present at the centre of the new system

So, flux through the new system = q/ε
flux through the cube given = 1/8 th of total flux (ex- contribution of corner atom to unit cell) = q/8ε

Now flux through each surface will be (q/8ε)/6 = q/48ε

NOTE (this is the average flux through each surface)

Different surfaces will have different flux through them. The three surfaces in contact with the charge q will have ZERO flux through them as E.S = 0 angle being 90°

I am not pretty sure abt this but i think the flux through the remaining three surfaces will be q/24ε each

106
Asish Mahapatra ·

Q2. Net capacitance of the system = 3C/2 . So, Energy drawn from the source = CV2 = 3CE2/2

1
cipher1729 ·

thats wat I was also thinking

but ans is given as 3CE2
this is a Q from Fiitjee package ,I don't know about the surety of this answer being correct

106
Asish Mahapatra ·

dunno then wat abt first question?

1
cipher1729 ·

that one is correct, thanks

Your Answer

Close [X]