A plate 130 mm wide is welded to a vertical plate by placing it on the vertical plate to form a cantilever with a projecting length of 600 mm and a overlap between the plates as 100 mm. Fillet welding is done on the three sides. A vertical load of 20 N is acting at the end of the cantilever. If the allowable stress in the weld is 80 MN/m2 . Determine the size of weld.
Answers
Ans: The situation is represented in the following figure.
A and B are two parallel plates close to each other. Outer region of plate A is labelled as I, outer region of plate B is labelled as III, and the region between the plates, A and B, is labelled as II.
Charge density of plate A,
Charge density of plate B,
In the regions, I and III, electric field E is zero. This is because charge is not enclosed by the respective plates.
Electric field E in region II is given by the relation,
Where,
=Permittivity of free space =
∴
Therefore, electric field between the plates is
NCERT Solutions class 12 physics Electric Charges and Field Part 225: An oil drop of 12 excess electrons is held stationary under a constant electric field of in Millikan’s oil drop experiment. The density of the oil is 1.26 g cm-3. Estimate the radius of the drop.Ans: Excess electrons on an oil drop, n = 12
Electric field intensity, E =
Density of oil,
Acceleration due to gravity, g
Charge on an electron, e
Radius of the oil drop = r
Force (F) due to electric field E is equal to the weight of the oil drop (W)
F = W
Eq = mg
Ene
Where,
q = Net charge on the oil drop = ne
m = Mass of the oil drop
= Volume of the oil drop × Density of oil
Therefore, the radius of the oil drop is