<h2>Given :</h2>
- total charge = 9.0 mC = 0.009 C
Each electron has a charge of :

For producing 1 Cuolomb charge we need :
Now, for producing 0.009 C of charge, the number of electrons required is :
_____________________________
So, Number of electrons passing through the cross section in 3.6 seconds is :

Number of electrons passing through it in 1 Second is :
Now, in 10 seconds the number of electrons passing through it is :
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Answer: Option A
Explanation:
The potential energy decreases in the case when the charges are opposite and they attract each other.
In this case there is no external energy required in order to put the charges together.
This is so because the charges are opposite and they will attract each other. Yes, the only condition should be that the charges should be alike.
Example: a negative charge and a positive charge.
Answer:
d. Two soccer balls that are touching each other
Explanation:
Let
be the mass of a tennis ball,
is the mass of a soccer ball.
As the mass of a soccer ball is more than the mass of a tennis ball, so

Let
be the distance between the centers of both the balls near each other and
be the distance between the centers of both the balls touching each other.
So, 
The gravitational force, F, between the two objects having masses M and m and separated by distance d is

Where G is the universal gravitational constant.
As, the gravitational force is directly proportional to the product of both the masses and inversely proportional to the square of the distance between them, so selecting the larger mass (
, soccer ball) separated by a lesser distance (
, touching) to get more gravitational force.
Therefore, there will be a larger gravitational force between them when two soccer balls touching each other.
Hence, option (d) is correct.
Answer:
<h2>Center of gravity of the system of all masses is 105 cm from the left end of the rod</h2>
Explanation:
Let the position of Left end of the rod is our reference
So here we will have










so we will have


