Unit 6 Blog Reflection

Physics Unit 6 Blog Reflection

            This unit we learned about major physics concepts involving electricity and more specifically; charges, charge transfer, polarization, electric fields, Coulomb’s Law, electric potential difference (voltage), current, types of current, source of electrons, Ohm’s Law, power, parallel circuits, and series circuits.

             Electricity a term used to represent a wide range of electrical phenomena that underlies everything around us. In order to understand a small portion of this huge part of life, we dissected it into different concepts. We began with electric charges. A charge can either be positive or negative. Protons have a positive charge and electrons have a negative charge, neutrons do not have a charge. Like charges repel; opposite charges attract. The transfer of electrons from one place to another causes charge. There are three ways for this transfer to happen; direct contact, friction or induction.  Direct contact and friction are self-explanatory for the most part. However, induction is a little bit more complex.  Induction happens when you bring a charged object near a conducting surface.

            Lightning is a good example of induction. Charging by induction takes place during thunderstorms. The clouds are negatively charged by friction and the clouds positively induce the ground.  The attractive forces eventually become strong enough to produce lightning. Therefore lightning starts from the ground, travels upward and then recedes toward the ground. This example also includes the idea of conductors versus insulators. Lightning rods are conductors. The main purpose of a lightning rod is to prevent a fire caused by lightning. Lightning rods are sharp, tall, and filled with positive charges. It will direct the lightning to the rod and to the ground rather than to the structure. The lightning is conducted into the ground rather than the house. Conductors allow the flow of electrical charge and insulators prevent the electrical charge. 

            Then, we learned about polarization. Induction can be found with conductors as well as insulators. Polarization is the separation of charges. A polarized object is still neutral because the charges are only separating; the electrons are not increasing or decreasing. An example we learned about that explains this as well as Coulomb’s Law is the reasoning behind why plastic wrap sticks to a ceramic bowl. The plastic wrap is charged by friction and when brought near the bowl, the bowl polarizes. The positive charges in the bowl move close to the negative plastic wrap and the negative charges in the bowl move away from the plastic wrap. The distance between the opposite attractive chargers is smaller than the distance between the like repelling charges. Coulomb’s law states that the force between any two charges are inversely proportional to the distance. F=kq1q2/d^2 Because there is a greater distance between the repulsive forces, the forces between them will be less than closer attractive forces. Therefore, the plastic sticks to the ceramic bowl. 

            Electric field is the area around the charge that can influence another charge. We draw electric fields in which direction a positive charge would pull. The closer the lines are together the stronger the electric field. The farther away you are from an electric field, the weaker it is. It is important to remember the difference between electric fields and gravitational fields is that various materials can shield electric fields, whereas gravitational fields cannot be shielded. Metal can completely shield an electric field. The electric field inside the metal encasing will feel no force by any charges outside of the shield. The filed inside will field no force no matter what. This is often why electronics are encased in a metal shield, so that the device inside of the metal case will feel no force outside of it, therefore it can function. 

            Next, we learned about the importance to know the difference between electric potential and electric potential energy. A charged object has potential energy through its location in an electric field. Electric potential energy is the energy a charge has due to its location in an electric field whereas electric potential, otherwise known as voltage and measured in volts, is equal to electric potential energy (in joules) over the charge (in coulombs). V=PE/Q.

            Following this we learned about electric energy storage. A capacitor is a common device where electric energy can be stored.

            The difference in potential energy is when the ends of an electrical conductor are at different electric potentials, charge flows(charge flowsàwhich is current) from one end to the other. The flow of the charge continues, as along as there is potential difference. When there is no potential difference, no charge flows. Charge flows when there is a high voltage and a low voltage and will stop when they are both an equal voltage. The rate of electrical flow, current, is measured in amps. Current will only work if there is a difference in electric potential. A key note to remember is that voltage causes current. Current does not cause voltage.

Take batteries for example. Batteries are able to have current because they have a difference in electric potential or a difference in voltage. Overtime, the difference decreases and eventually there is no longer an electric potential difference. When there is not an electric potential difference, there is no current, which is why batteries stop working.

Another example explains why flashlights get dimmer as the battery becomes weaker. A flashlight gets dimmer as the battery becomes weaker because the difference in voltage decreases, voltage causes current and the less current there is to light the bulb, the dimmer it will be.

Also, the idea that to complete a circuit, there must be current. This current comes from the potential difference from the high voltage to the low voltage. This is why birds aren’t harmed when sitting on a power line wire. If birds are standing on only one wire, they are not completing the circuit because they aren’t touching the ground (which would conduct electricity through their bodies and into the ground) and they aren’t touching the two wires at the same time. This means there’s no current meaning that there is no electric potential difference.

The amount of current that exists depends on the voltage as well as the electrical resistance, the conductor, which offers the flow of charge. The resistance of a wire depends on the thickness, length, and material. The thicker, the shorter, and the better conductor material, and the colder the wire is, the wire is the less resistance there will be meaning there will be more current. Electrical resistance is measured in ohms. 

Ohm’s law states that current in a circuit is directly proportional to the voltage and is inversely proportional to the resistance of the circuit. Current(amps)=voltage(Volts)/resistance(ohms)

Electric shock can be damaging from the current passing through the body. This current that runs through your body depends on both the voltage used and the electrical resistance of the body. To receive a shock, requires a difference in electric potential from one part of your body to another part. As long as you are wearing some sort of insulator or you are standing on an insulator, or you are not completing the circuit, you will not feel any shock not allowing the current to run through your body.

Another key factor to keep in mind is that “high voltage” does not necessarily mean high danger; the danger factor rests upon the amount of stored energy there is.

Look at this plug, the round prong connects the rest of the appliance directly to the ground. Any charge built up on the appliance is then conducted to the ground, which prevents accidental shock. We briefly discussed direct current and alternating current. Electric current can come in two forms; dc or ac. DC is direct current, which refers to the flowing of charges in ONE direction. A battery uses direct current. AC is alternating current, which moves in one direction and then the opposite direction and moves in this path continuously. Households use AC current.

            Think about flipping on a switch to a light in a room. The lights work immediately when the circuit is completed. Current is established through the wires at nearly the speed of light. It is not the electrons that are moving quickly, in fact the electrons are moving very slowly but the electric signal moves nearly at the speed of light. Another misconception about electrons is the idea that electrons flow from the outlet into a lamp but it is actually, when you plug a lamp into an outlet, energy flows from the outlet into the lamp.

            Moving onto electric power, electric power is equal to current times voltage. P=IV and the relationship between energy and power is simply. Power=Energy/Time

            The last concept we covered was electric circuits. A circuit is any path along which electrons can flow. There are two types of circuits; series and parallel. A series circuit has all devices connected end-to-end, which forms one path for electrons to flow. The more appliances added the more resistance increases, current decreases, brightness (power output) decreases, and when one light bulb stops working or is removed, they all stop working. A parallel circuit has electrical devices connected to the same two points. The pathway for current from one end of the battery to other is completed if only one light bulb is lit rather than all light bulbs in the circuit.  The more appliances or light bulbs added to the circuit the resistance decreases, the current increases, the brightness remains constant and when one light bulb stops working, the rest are not affected. Households use parallel circuits because it is more efficient. Parallel circuits allow households to run multiple devices without running other devices unlike series where it is all or nothing. The only major disadvantage to parallel circuits is the heat factor. The more current and less resistance there is (which happens the more devices are on), there is high heat, which could potentially turn into a fire. A fuse/circuit breaker prevents this from happening. A fuse is used to prevent the current from getting to this dangerous level. The fuse melts and snaps turning the circuit off. A fuse is used in parallel circuits but it is set up in series. 

            This unit has been particularly challenging for me. I struggled with understanding each and every concept we learned to its fullest because there were so many concepts to go over. I became frustrated with learning the process of lightning, capacitors, and the difference between electric potential and electric potential energy. The confusion with these concepts lead me to not do as well on quizzes that I would have liked. 

             However, I overcame these struggles by taking each concept step by step. I went through the book and looked the examples used and compared them to my notes. I was able to use more detail with the examples and have a better understanding of each one. Also, I went through each quiz and corrected what I got wrong so that I could understand it more clearly and not mess up on the test. 

             My problem solving skills this unit were slow but comprehensive. I tried my best to understand the material I was unclear about. I went in for help various mornings, usually before quizzes. I always completed my homework in detail and corrected my answers in class if I got questions wrong. I think labs were particularly useful for me as well as group work because our groups could bounce information and answers off one another without a group shutting down the other group.