Electric forces can be attractive or repulsive because charges may be positive or negative. In the case for gravitational forces, there are only attractive forces because mass is always positive.

We can calculate this using Coulomb’s Law

In Coulomb's law, an increase in both interacting charges will cause an increase in the magnitude of the electrical force between them. Specifically if the magnitude of both interacting charges is doubled, this will quadruple the electrical force.

We will need to use Coulomb’s Law to analyze the force on the 3Q charge from all the other forces.  We will then summarize the net force in the  and  direction to determine the force on the 3Q charge.

In the x-direction

Force from 4Q on 3Q

Force from Q on 3Q in the x direction

Add these together in the x-direction 

In the y-direction

From from 2Q on 3Q

Force from Q on 3Q in the y direction

Add these together in the y-direction 

Now we can find the resultant of these sides using the Pythagorean theorem.

The power in a circuit is equal to the current times the voltage.

Current is defined as the amount of charge that passes through a specific area of a wire in a specific interval of time.  It is measured in Amps which are Coulombs per second.

Decrease to one half its original value

The equation for Power is 

According to Ohm’s Law

We can rearrange this equation for current as this is what is changing in our circuit.

We can then substitute this back into the power equation.

If we have the original value

  and our second value

We can rearrange both for the voltage and set them equal to each other

, 

We know that

So we can substitute this value in

And solve for 

Therefore the power would be cut in half.

The current is a measure of the amount of charge that passes a given point in a certain amount of time.

To determine how many electrons are passing this point we need to look at the charge of 1 electron and do a conversion.

We often think of current flowing from the top of the battery to the bottom of the battery.  The top of the battery has a higher electrical potential than the bottom of the battery and is associated as being positive.  Charges interact in such a way where like charges repel and opposite charges attract.  Since we think of the charges traveling away from the positive end of the battery and toward the negative end of the battery, this would model the motion of a positive charge (away from positive and toward negative).  Since it is not protons that move through the circuit, but rather electrons.  It is more accurate to describe the flow of electrons from the negative side of the battery to the positive side.

When plugin objects into a single circuit, these objects are connected in parallel as each one will receive the 120V from the electrical outlet. However, as additional objects are added, the current is thereby increased. Circuit breakers are designed to trip once the current reaches a maximum load and shuts down the circuit to protect the wires, and the devices that are plugged into the circuit as high current can damage these devices.