Multimeters!!

Recently, we've been dealing a lot with these things called multimeters in physics class.

Well, what is a multimeter, you ask?
A multimeter is an instrument designed to measure electric current, voltage, and resistance.

We have been using multimeters in class to understand currents, voltages, and resistances in schematic circuits drawn on the board with a D battery as the voltage source. We learned that when you use a multimeter, you must measure "voltage across, current through". When measuring voltage, you measure from one side of the resistor (lightbulb, wire, etc.) to the other. When measuring current, you must break the circuit and connect the probes between to measure the flow.

What can you use a multimeter for other than for physics experiments and diffusing bombs?
You can use a multimeter for all sorts of things. Within a circuit in your house, you can use the multimeter to check where the break or shortage. You can save money by getting straight to the problem instead of hiring someone else to do it or throwing the device away! For example, if you have a device that is using an ac/dc converter that stops working, how can you tell if it is the converter or the device? Instead of just buying a new device or converter, you can use a multimeter to understand the root of the problem!
You can also use a multimeter to test if your batteries still have voltage in it. Multimeters are useful for testing ac/dc converters, fuses, lightbulbs, wall switches, wall outlets, and most electronic devices in your household!

Electricity Lab!!

Did you know that Hawaii is ranked #1 in the nation for the highest energy costs? The United States average usage is 11-12 cents per kilowatt-hour, while the island of ‘Oahu’s average is close to triple that, with 33.22 cents per kilowatt-hour. These high electricity costs come because of our dependence on foreign oil and our isolated location.

In ancient Hawaii, Hawaiians were sustainable and efficient. They were not exposed to electricity and could function as one of the most effective and organized groups of ancient people. As Hawaiians, we should continue as our ancestors did by living a sustainable life. Although we rely on electricity for our everyday lives, we can restrict our usage to conserve our limited resources while at the same time saving money.

Through this experiment, we can learn the factors dealing with electricity and how to be less dependent on foreign electricity like our ancestors were. The purpose of this experiment is to understand electricity as a whole to better conserve our limited energy source and even save a little money on the side.

I hypothesize that if my family cuts out specific electricity-consuming appliances, we can save at least $10 on our electricity bill!

There are many variables that we must understand to be successful in this lab. A dependent variable is the output or effect of the experiment. This would be the amount of electricity used or the amount of money saved. An independent variable is the input of the experiment that can be manipulated. These variables may include months or changes in our electricity usage. A control is a factor that is kept constant to minimize the amount of variables. A control for this experiment could be testing the same house or building for the changes in electricity usage.

The basic procedures for my lab are as followed:

1.          Collect electric bill from the previous month.

2.         Go to appliances in the house or building.

-      Assess the amount of electricity each appliance uses and find out which uses the most electricity and which is most frequently used.

3.          Decide to cut the amount of the appliance used by a sufficient amount that will be ideal to lower the monthly bill while also fitting with the family’s lifestyle. (For example: Hang dry all clothes for a month, lower water heater temperature, no AC for a month)

-      Continue for a month.

-      Log down hours and power used for each appliance.

4.         At the end of the month, receive your electric bill and compare the two.

     I have collected data for some time now and will continue until the end of the month! Go Green!

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!

Electric Potential!!

In the upcoming unit, we will be learning about a new concept: electric potential! Electric potential is the potential energy per charge.

Electric Potential = PE/q

Electric potential is measured in volts (V) or Joules per Coulombs (J/C). The website, Physics Classroom states that, "the concept of electric potential is used to express the affect of an electric field of a source in terms of the location within the electric field." From this website, I found that an object with twice the charge will experience twice the potential energy when placed in the same location. Despite this, the electric potential is the same.

I also learned that a battery powered electric circuit has locations of high and low potentials. The charge moves through the wires and change in electric potential. There is an electric field created within the electrochemical cells of a battery between two terminals.

We will learn a lot more and expand our knowledge in this subject in the upcoming week!

Electrostatics!

Kicking of the new year with a new unit:

Electrostatics!

This unit relates back to chemistry, involving positive, negative, and neutral charges, and their attraction to each other.

Lets review what we learned in chemistry:

The three types of charges in an atom are protons, neutrons, and electrons. Protons have a positive (+) charge, neutrons are neutral, and electrons hold a negative charge (-). The protons and neutrons are located within the nucleus and the electrons surround the atom.

One of the first things that we learned in this unit was that like forces (forces with the same charge) will repel, unlike charges (forces with different charges) will attract, and neutral charges have no effect on each other.

We also learned about conductors and insulators. Conductors allow charges to move more freely, whereas insulators like to hold onto electrons (charges don't move as freely).

Below are the new electrostatics equations that we added to the board not bored:

(1) Inverse Square Law: F α 1/r^2 (the force upon an object is going to be inversely proportional to the square of the distance between the objects.)

F = force

r = distance

(2) The Universal Law of Gravitation: F = G(m1*m2/r^2)

m = mass

r = distance

G is a constant

(3) q = ne^-

q = charge (C)

n = number of charges

e^- = charge of one electron

(4) Coulomb's Law: Fe = k*q1*q2/r^2

(5) E = F/q

My friends and I went out a little while ago to Spaghetti Factory, where we got ballon hats during dinner! These balloon hats needed to be put on a certain way to make sure it wouldn't fall off, which required a lot of moving/rubbing of the balloon against our hair. When we took the hats off for a nice picture, all of our hairs were standing up! (So we had to take it with the balloon hats on haha) Why did this happen? Magic? No, physics! When the balloon rubs against the hair, the hair becomes more positively charged while the balloon gets negatively charged. These unlike charges attract to one another, so when the balloon is lifted up, the hair goes with it too!

There's still a lot more to learn about electrostatics!