Answer:
the electric field is 42.8×10^6 N/C
Explanation:
let k be the coulomb constant, Q be the charge distribution , R be the radius of the disk and x be the distance from the center.
k = 8.98755×10^9 N×m^2/c^2
Q = 6.1×10^-6 C
R = 4.9×10^-2 m
x = 3.1×10^-3 m
The current intensity is defined as the amount of charge Q that passes through a certain point of an electrical wire in a time interval of
:
In our problem, the current intensity is
while the amount of charge that passes a certain point of the wire is
If we re-arrange the previous equation:
we can find the time needed for this amount of charge to pass through a point of the wire:
The graph is missing, however we can answer anyway.
In fact, this is the approximate percentage of the elements listed in the questions in the Earth's crust (data taken from wikipedia):
Iron 5.0 %
Calcium 3.6 %
Sodium 2.8 %
Potassium 2.6 %
Magnesium 1.5 %
of all of these, we see that the combination of two elements that makes up the closest number to 7% is calcium and sodium (3.6% + 2.8%=6.4%), therefore the correct answer is
Calcium and sodium.
Heat flows naturally from a warmer object (higher energy) to a cooler one (lower energy).
