Right-hand rule #1: Hold the conductor with your right hand. Your thumb should be pointed in the direction of the conventional, or positive current flow. Your fingers should be pointing in the direction of the magnetic field around the conductor.

Right-hand rule #2(for coils): Hold the coiled conductor with the right hand such that the curved fingers point in the direction of conventional or positive current flow. The thumb points in the direction of the magnetic field within the coil. Outside the coil, the thumb represents north end of the electromagnet produced by the coil.

Magnetism

A magnetic force is a force that acts from a distance. A magnetic field is the distribution of a magnetic force in the region of a magnet.


A magnet usually contains two magnetic poles, north and south. Similar magnetic poles, like north and north or south and south, repel each other with force. Dissimilar poles, like north and sough, attract each other with force.


Only nickel, iron and cobalt are attracted to magnets so they are known as ferromagnetic metals.
 The Domain theory states that all large magnets are made up of many smaller and rotatable magnets, known as dipoles. Dipoles can ineract with other dipoles close by. If dipoles line up, then a small magnetic domain is produced.

Oersted's Principle: Charge moving through a conductor produces a circular magnetic field around the conductor.

Resistance, Ohm's Law, and Kirchhoff's Laws

The amount of energy transferred to any device depends on two things:
1. The potential difference of the power supply.
2. The nature of the pathway through the loads that use the electric potential energy.

The amount of current flowing through a resistor changes depending on the amount of energy that's put in the resistor.


A thin wire will have more resistance, while a larger one will have less.
In order to calculate resistance, we use the formula R=V/I. Where R is the resistance in ohms (Ω), V is the potential difference in volts and I is the current in amperes.

The ratio between Voltage against Current is constant and is known as Ohm's Law.

Kirchhoff's Current Law: The total amount of current into a junction point equals the total current that flows out of the same point.


Kirchhoff's Voltage Law: The total of all electric potential decreases in any complete circuit loop is equal to any potential increases in that circuit loop.
 
Kirchhoff's laws apply to the laws conservation of electric charge and the conservation of energy. To make it short, in any circuit, there is no net gain or loss of electric charge or energy.

Today, Mr. Chung gave us a prelab to do to prepare for the lab we are going to do tomorrow. We were asked to fill out this chart:


NAME                       SYMBOL                      UNIT                    DEFINITION

Voltage                            V                           Volts         An electromotive force or
                                                                                    potential difference expressed
                                                                                    in volts.

Current                             I                         Amperes    A flow of electric charge
                                                                                  through a conductor. The rate
                                                                                  of flow of a charge. Current is
                                                                                  measured in amperes.

Resistance                       R                          Ohms        A measure of the degree to
                                                                                  which a substance impedes the
                                                                                  flow of electric current induced
                                                                                  by a voltage. Resistance is
                                                                                  measured in ohms.

Power                               P                         Watts       The rate at which work is done,
                                                                                  expressed as the amount of
                                                                                  work per unit time and
                                                                                  measured watts.

The Energy Ping-Pong Ball and Parallel/Series Circuits

So last friday, we were given an activity by Mr. Chung. The activity involved these 12 questions we had to answer and an energy ball which Mr. Chung refers to as a ping-pong ball. The ping-pong ball lights up when

Question 1: Can you make the energy ball work? What do you think makes the ball flash and hum?
Yes, we can make the ball work by touching and holding the 2 metal contacts with two of our fingers. What makes the ball light up and hum? Ourselves. Humans are conductors so when we touch the metal contacts, the current flows and the ball lights up.

Question 2: Why do you have to touch both metal contacts to make the ball work?
So that the circuit will be complete and the current can flow through the ball.

Question 3: Will the ball light up if you connect the contacts with any material?
Only materials that are conductors will make the ball work.

Question 4: Which materials will make the energy ball work? Test you hypothesis.
Since the material has to be a conductor, our fingers and metals should make the ball work.

Question 5: This ball does not work on certain individuals, what could cause this to happen?
Those certain individuals most likely have dry skin. In order for the circuit to work, one should have enough mositure in their hands so that the circuit can flow properly.

Question 6: Can you make the energy ball work with your group? Will it work with the class?
Yes, our group was able to connect and make a circuit that allowed the ball to light up.

Question 7: What kind of circuit can you form with the energy ball?
The circuit we made with the one energy ball is a simple circuit.

Question 8: Given two balls (combine with another group) can you create a circuit where both balls light up?
Yes, we were able to connect another ball into the circuit and made both balls light up.

Question 9: What do you think will happen if one person lets go of the other person's hand and why?
The circuit becomes incomplete and both balls will not light up.

Question 10: Does it matter who let's go? Try it.
No, it doesn't matter who let's go because there is only one path in the circuit. Anyone that let's go will break the path and thus the circuit.

Question 11: Can you create a circuit where only one ball lights (both balls must be included in the circuit)?
Yes, but in order to do that, we need to make a parallel circuit.

Question 12: What is the minimum amount of people required to complete this?
Just one. One person can hold each ball in one of their hands with their fingers. If they let go one finger on a ball, that ball will stop working, but the other ball will continue to flash.

So what's the difference between a series circuit and parallel circuit? A series circuit only has one continuous path, while a parallel circuit has more than one path. This means that in a series circuit, if the path becomes broken anywhere in the circuit, the load will instantly stop working. But in a parallel circuit, if the path becomes broken, at least 1 load will work while another would stop working.

Newspaper Tower

The other day, we were making newspaper towers to see which group can make the tallest stable structure. At first, we came up with many different ideas for how we should make the tower, but we didn't seem to agree on which idea we should use. Evantually, we came to a comprimise and made our tower with components from each idea.

The physics of our tower was that the base was to be as big as possible so that it could support the cylindrical newspapers above it. As we got higher and higher though, we realized that our base wasn't big enough, as the tower kept leaning to the side. So, in order to keep the tower standing, we added a coned-shape newspaper under the big base in order to keep the tower standing. This could've worked, but then we saw that the tower was barely able to stand on its own due to the fact that the upper part of the structure was too heavy. We realized this when we were evaluating all the towers that were built in the class. It seems that in order to make a tall structure stable, we should've made our tower's upper part with less weight. Since we were using cylindrical newspaper, the tower has more weight on the top and thus is more prone to falling.

Our tower was pretty muched scrapped at the end, so I don't have a picture to show D=

Current Electricity and Electrical Potential

An electric current is the flow of charge through an electric circuit. Current is the rate of charge flow and is represented by the symbol I.

The unit that represents current is C/s which is also called an ampere. Current can be calculated by the formula I = Q/t where I is the current in amperes, Q is the charge in coulombs, and t is time in seconds.

An ammeter is a current-measuring device that must be wired so that all current can flow through it. The ammeter must be a good conductor so that no energy is lost when it's added into the circuit.

In Direct Current or DC, current flows in one direction from the power supply, through the conductor and ends at the load. In Alternating Current or AC, the electrons can reverse their direction with the help of electric and magnetic forces.

In a circuit, electric potential difference is the electrical potential energy for each coulomb of charge in a circuit. It is represented by the symbol V. Electric potential energy can be calculated by the formula
V = E/Q. E is energy and Q is the charge. Potential difference can also be called voltage.