Current Density Vector

Q. Paragraph A very long thick plate has a uniform positive volume charge density given by p(x)= p° for -d/2 < x < d/2 . where p° is a positive constant, d is the thickness of the plate and x = 0 is the centre of the plate. Q1) what is the symmetry of the electric field for this object ? Q2) how much charge is contained in a gaussian pillbox of cross sectional area A and thickness 2a , where a < d/2 ? a) p°Aa (b)2p°Aa (c)p°Aa/2 (d)4p°Aa Q3) use gauss law to find E(a) _____. Q4) how much charge is contained in a gaussian pillbox of surface area A and thickness 2a , where a > d/2 ?

Q. An electric current of 8 Amperes is measured across an area of $50c{m}^2$, then current density in this area is:

1. Must be $1600A/m^2$
2. Must be greater than or equal to $1600A/m^2$
3. Must be less than or equal to $1600A/m^2$
4. Cannot say

Q.

A wire of ${10}^{-3}c{m}^2$ cross sectional area carries a current of 0.25 A, then current density is

1. $1.5\times {10}^{6}A{m}^{-2}$

2. $2.5\times {10}^{6}A{m}^{-2}$

3. $3.5\times {10}^{6}A{m}^{-2}$

4. $4.5\times {10}^{6}A{m}^{-2}$

Q. A copper wire of length 1m and radius 1mm is joined in series with an iron wire of length 2m and radius 3mm and a current is passed through the wire. The ratio of current densities in the copper and iron wire is

1. 18 : 1
2. 9 : 1
3. 6 : 1
4. 2 : 3

Q. Due to the electric field, the electrons inside a conductor continuously accelerate.

1. True
2. False

Q. Which of the following quantites are scalars?

1. Current
2. Current density
3. Field
4. Potential
5. Charge
6. Energy
7. Force
8. Power