Answer:
Explanation:
The point at which magnetic field is to be found lies outside wire so while applying Ampere's law we shall take the whole of current . If B be magnetic field which is circular around conductor.
Applying Ampere's law :-
∫ B dl = μ₀ I      ; I is current passing through ampere's loop
B x 2π x 2.00 = 4 x π x 10⁻⁷ x 2
B = 2 x 10⁻⁷ T. 
 
        
             
        
        
        
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The average radius(r) of each grain is r = 50 nanometers
= 50*10^-6 meters 
Since it is spherical, so
 Volume=(4/3)*pi*r^3 
V= (4/3)*pi*(50*10^-6)^3 
V=5.23599*10^-13 m^3 
 
We are given the Density(ρ) =2600kg/m^3 
 
We know that:
Density(p) = mass(m)/volume(V) 
m = ρV
 
So the mass of a single grain is: 
m = 5.23599*10^-13 * 2600 = 1.361357*10^-9 kg 
 
 
The surface area of a grain is: 
a = 4*pi*r^2 
a = 4*pi*(50*10^-6)^2 
a = 3.14*10^-8 m^2 
 
 
Since we know the surface area and mass of a grain, the
conversion factor is:
1.361357*10^-9 kg / 3.14*10^-8 m^2 
 
Find the Surface area of the cube: 
cube = 6a^2 
cube = 6*1.1^2  = 7.26m^2
 
multiply this by the converions ratio to get: 
total mass of sand grains = (7.26 m^2 * 1.361357*10^-9 kg)
/ (3.14*10^-8 m^2) 
total mass of sand grains = 0.3148 kg = 314.80 g