List and explain briefly similarities and differences between the electric force between two charges and the gravitational force between two masses.

Please see below as the answers are self-explanatory.

Explanation:

1) The resultant force is along the line that joins both charges or both masses (assuming both objects can be represented as points)

2) Both type of forces obey  Newton's 3rd law.

3) Both are proportional to the product of the property that is affected by the force (charges and masses)

4) Both obey an inverse - square law (consequence of our universe being three-dimensional)

1) Main difference, is that while the gravitational force is always attractive, the electrostatic force can be attractive or repulsive, as there are two types of charges, which attract each other being of different type, and repel each other if they are of the same type.

2) It  is possible, artificially, to block the influence of the electrostatic force, shielding a room, for instance, which is not possible for the gravitational force.

power out to power in less than 100%

v=ir = 3x15 =45 v