Electric Charge Practice Problems
Two tiny iron balls to be used in an electrostatics experiment have a mass of 0.0550 kg each. The balls are placed 65.0 cm apart. Determine the number of electrons on each neutral ball. (Iron has an atomic mass of 55.85 g/mol and atomic number 26)
Electricity is the flow of charges, generally electrons from high potential to low potential. A circuit breaker is rated at 6300 A (1A = 1 C/s). The breaker will trip if this maximum current is sustained for 50 ms. Determine the i) amount of charge that will flow within that time and ii) the number of electrons that flow within that time.
A rod of radius B is charged to a linear charge density λ. The volume charge density inside the rod (b ≤ B) is described by ρ (b) = bρ0 / B, where ρ0 is some unknown constant and ρ(b) has units C/m3. The charge on a volume element dV is dq = ρ dV. To get the total charge (Q = λY), we integrate dq = ρ dV over the entire length (Y) of the rod from zero to the radial length B. Determine the value of ρ0 in terms of λ and B. Hint: Find the volume of an element dV of length Y, radius b, and thickness db.
A bar of length 1.5L is placed parallel to the x-axis. The origin of the x-axis is located at (3L/4) and is measured from the left end of the bar. The charge on the bar varies as λ=b|x|, where the constant "b" has units C/m2. Sketch a graph of λ versus x for the total length of the rod.
Charged organic matter is used to cast a sphere of radius 125 mm and has a total charge of 60 nC. Assuming that there is even charge distribution, calculate the charge enclosed by a spherical surface with a radius of i) 20 mm and ii) 60 mm.