Series and Parallel Circuits!

In our electricity unit, we are learning about series and parallel circuits!

Series Circuit!

A series circuit has one path. The voltage is shared along the path and the higher resistance resistor will receive more voltage. All resistors in a series circuit on the same path with get the same current (one path, one current). The equivalent resistance of a series circuit is the amount of resistance that a single resistor needs to equal the overall affect of resistors in the circuit. For example, three 7Ω resistors would be equivalent to a 21Ω resistor. The equation to find the total equivalent resistance (Req) is

Req = R1 + R2 + R3...

To find the total current from the battery we use V = IR with the givens.

Ibatt = Vbatt / Rbatt

To find the voltage drop across three resistors, we use V = IR for all resistors and then add them together.

Let's find the Req! (pretend the kΩs are just Ω)
Req = R1 + R2 + R3
Req = 3Ω + 10Ω + 5Ω
Req = 18Ω

Let's find the Ibatt!
Ibatt = Vbatt / Rbatt
Ibatt = 9V / 18Ω
Ibatt = 0.5 A

Let's find the V drop! 
V = IR
1. 1.5V
2. 5V
3. 2.5V
V = 9V

Parallel Circuit!
Parallel circuits have multiple paths or branches. The difference between the series and parallel is that if one resistor is cut off of a parallel circuit, the circuit can still work. If a battery was cut off of a series circuit, the current wouldn't be able to flow. Voltages in a parallel circuit are the total start voltage down the path.
The current total is equal to the sum of all currents

Itotal = I1 + I2 + I3

The Rtotal or Req of a parallel circuit is shown by this equation

1 / Req = 1 / R1 + 1 / R2 ...

We can see series and parallel circuits in our everyday life! 

Series A series circuit can be seen in Christmas lights! If you take one light away, they all go out.

Parallel A parallel circuit can be seen in a power strip! Each flow of electric current is separated.

Its Electric!

What is electricity?
Electricity is associated with the stationary or moving of electric charges - or more simply, the flow of electrical charge. In the nucleus, there are positive and neutral charges called protons and neutrons. The nucleus is surrounded by negatively charged particles called electrons. Electricity is the result of the buildup or motion of electrons and is measured in units called Watts.

What is the importance of electricity?
Electricity has become a necessity to most people in the 21st century. Almost anywhere you look, you can see the workings of electricity. There is electricity in the TV downstairs, in the lights powering a soccer field, and even in the laptop I am writing on right now. Even items that were packaged and manufactured, like food and ordinary household items, have been touched by electricity. Electricity keeps us moving everyday.

What is electric current?
Electric current is the flow of electricity through a conductor and is measured in coulombs per second or amperes. The particles that carry charges through the circuit are called mobile electrons. The direction of an electric current would move towards the positive charges.

I = Q / t

Where Q is charge and t is time.

What is resistance?

The electrical resistance is the ration of the voltage applied to the electric current that it flows through. This definition is shown as 

R = V / I

Ohm's Law says that the electric current is the directly proportional to the voltage and indirectly to resistance. This is shown as 

I = V / R

If it is constant over a certain range, then Ohm's law can be used to predict the behavior of material.

Resistance is temperature dependent.

Now we know more about electricity!

Capacitance!!

After learning about electric potential, we are starting to concentrate on something called "capacitance". So what exactly is capacitance?

Well, a capacitor is an electronic component that can be charged and can store charge. It has the ability to reach across an insulator and is made of two flat plates made of conducting metal. The two plates are connected to a terminal so that a voltage can be applied.

When a capacitor is being charged, the negative charge is taken out of one area and put into another, leaving one side with a negative charge and the other with a positive charge. Although charges are being rearranged, the net charge of the whole remains at zero.

From the website, Physics.sjsu.edu, I learned that "The amount of charge that can be placed on a capacitor is proportional to the voltage pushing the charge onto the positive plate. The larger the potential difference (voltage) between the plates, the larger the charge on the plates."

Q = C V

I also learned that, "The constant of proportionality is called the "capacitance" and is proportional to the area (A) of one of the plates and inversely proportional to the separation between the plates (d): 

C = e A / d

for a parallel plate capacitor.

We encounter capacitors in everyday life almost every day! This is because every electronic and most electric appliances have capacitors. They are used for energy storage filtering, and many more uses! If you look around you, I'm sure you can find at least three: your TV, cellphone, radio, and the laptop you are viewing this on!

During this week, we will be able to broaden our knowledge on capacitors!