Answer:

Explanation:
Given that


Emissivity of surfaces(∈) = 1 
We know that heat transfer between two surfaces due to radiation ,when both surfaces are black bodies

So now by putting the values



So rate of heat transfer per unit area 

 
        
             
        
        
        
Explanation:
Given that,
Charge on a spherical drop of water is 43 pC
The potential at its surface is 540 V   
(a) The electric potential on the surface is given by :

r is the radius of the drop

(b) Let R is the radius of the spherical drop, when two such drops of the same charge and radius combine to form a single spherical drop. ATQ,

Now the charge on the new drop is 2q. New potential is given by :

Hence, the radius of the drop is  and the potential at the surface of the new drop is 856.79 V.
 and the potential at the surface of the new drop is 856.79 V.
 
        
             
        
        
        
 675g/cm³ is the density of the liquid 
Here we have given that
density of wood be ρ.
the volume of the block be V          
The volume of the block =1/4 v
The volume of the immersed block (v) =V-1/4V=3/4V
We know the weight of the block = the weight of the water displaced by the submerged part of the block.
i.e. V x ρ x g    
 = 3/4 x900g/cm³                            
 = 675g/cm³
Density is a measure of mass divided by the volume of an object. Defined as mass per unit volume. here from the above equation we have substituted the given value and  we got the answer as  675g/cm³ 
        
Learn more about Density here brainly.com/question/1354972
  
#SPJ9
 
        
             
        
        
        
Answer:
a)    V = - x ( σ / 2ε₀)
c)  parallel to the flat sheet of paper
Explanation:
a) For this exercise we use the relationship between the electric field and the electric potential
           V = - ∫ E . dx        (1)
for which we need the electric field of the sheet of paper, for this we use Gauss's law. Let us use as a Gaussian surface a cylinder with faces parallel to the sheet
        Ф = ∫ E . dA =  /ε₀
 /ε₀
the electric field lines are perpendicular to the sheet, therefore they are parallel to the normal of the area, which reduces the scalar product to the algebraic product
           E A = q_{int} /ε₀
area let's use the concept of density
         σ = q_{int}/ A
        q_{int} = σ A
           E = σ /ε₀
as the leaf emits bonnet towards both sides, for only one side the field must be
           E = σ / 2ε₀
          we substitute in equation 1 and integrate
       V = - σ x / 2ε₀  
        V = - x ( σ / 2ε₀)
if the area of the sheeta is 100 cm² = 10⁻² m²
       V = - x  (10⁻²/(2 8.85 10⁻¹²) = - x  ( 5.6 10⁻¹⁰)
        
       x = 1 cm     V = -1   V
       x = 2cm     V = -2   V
This value is relative to the loaded sheet if we combine our reference system the values are inverted
        V ’= V (inf) - V
        x = 1 V = 5
        x = 2 V = 4
        x = 3 V = 3
    
These surfaces are perpendicular to the electric field lines, so they are parallel to the sheet.
  
In the attachment we can see a schematic representation of the equipotential surfaces
b) From the equation we can see that the equipotential surfaces are parallel to the sheet and equally spaced
c) parallel to the flat sheet of paper
 
        
             
        
        
        
Answer:
Gasoline will float
Asphalt will sink
Cork will float
Explanation:
Simply compare the value of each object's density to that of the sea water (1.025 g/ml). If the density of the object is less than that of the water, the object will float due to the buoyance force.
Contrarily, if the density of the object is larger than that of sea water, the object will sink.
Gasoline, with density 0.66 g/ml which is less than that of sea water, will float.
Gasoline, with density 1.2 g/ml which is more than that of sea water, will sink.
Cork, with density 0.26 g/ml which is less than that of sea water, will float.