Unit 6 Review

Unit  6 was a fun and interesting topic, during this unit we learned 5 main concepts, such as, Electricity, Electric Fields, Electric Potential, Power, and Types of Currents; with these in mind there were also many smaller sub categories. It was a great unit and looking forward to the next unit and and doing our podcast.

Electricity
      There are three ways to make something charged, one way is through friction i.e. static electricity (imbalance of electric charges within or on the surface of a material), another way is through contact i.e. (person touching person), and lastly, induction i.e. (lightning).

To be positively charged, an object must have more protons than electrons  for something to be negatively charged it must have more protons, and for something to be neutral it must have the same amount of protons to electrons.

So when you take off a sweatshirt or winter hat, it steals the electrons through friction, the sweater/hat now become negatively charged and the hair becomes positive. Therefore the hairs repel from one another because the are like charges.

Another of how electricity and charges are transferred is through laundry. When clothes are in the dryer, they rub together and become negatively charged through friction. When clothes steal electrons from other clothes those become positive and then the two opposite charges attract, so clothes stick together. 

Lightning works in magical ways, it works by something called induction (makes the ground + by induction, rain clouds rub together become -).  But how do lightning rods protect a building?
Lighting rods protect structures by forcing the electrons and protons (lightning) to make contact with the metal rods that are connected to a wire that lead into the ground. Therefore no damage to building. Now, charges like to build upon pointy objects these are positive charges, the clouds are full of negative charges because of friction. Should the path from the clouds to the wire been completed, the energy gets routed to the wire that leads into the ground. So house=safe.

Polarization

So why does plastic wrap stick to glass bowls but not metal bowls?

To answer this question we must know a few things, there are two things that can affect how something becomes polar, those are conductors (lets charges move through objects) and insulators (stops charges from moving). Metal is an conductor and glass is a insulator. 

Okay so when the plastic wrap is unrolled, it is charged through friction and when it is brought near the glass bowl the bowl polarizes. The positive charges move closer to the more negative charges in the plastic wrap and the negative electrons in the bowl move away from plastic wrap. The distance between the opposite charges is smaller than that of the repelling charges. Coulomb's law states F=kq1q2/d^2 . Since the distance between the attractive forces is closer than the reclusive forces the attractive forces will have a stronger force between them.

So one take away from all this is Coulomb's law F=kq1q2/d^2, which means that the charge that is closer to the other force will have a stronger force.

Electric Fields and Shielding

Have you ever wondered why electronics are in metal cases? 

Well there is a thing called an electric field and it is an area around a charge that can influence (push/pull) another charge. HOWEVER, a metal case does not allow there to be electric fields, so they cannot influence anything inside the container. Electronic hardware is very sensitive, so they are placed in metal containers and once inside no matter where the electrons or protons are in this container it will feel no force because the forces are evenly distributed.

Electric Potential

This is a jam packed category so just stick with me! 

So in this category there is a misunderstanding between volts and voltage.

Volts is the electric potential but voltage is the difference between the electric potentials. 

To find how much voltage is in something we must use the equation V=PE/q or V=J/c

And to find the current of something we must use the equation I=V/R and current is measure in amps, and resistance (R) is measured in ohms. 

If there is no way there can be a current without voltage! 

How do flashes work? 

In order for a camera to have a flash it must have three things, a capacitor and two oppositely charged wires. But these wires are not connect in fact the two build up charges and the more charges built up the larger the force and energy of the electric field between the two plates will be. When the two wires briefly connect, the energy rushes from the high energy to the low energy and is released as light thus the flash. The voltage between the two wires is higher than those things around it so it has a slightly larger voltage.

How can something have a higher voltage but not be as dangerous as something with a lower voltage?

V=J/c --> 100=100/1 compared to 50=2500/50

Why is it dangerous to plug an American appliance into a European country?

It is dangerous because in America the circuits put out 120V but in Europe they put out 220V. So when you plug in an American appliance in it will have a much smaller resistance and the current will be much larger than it should be making it very hot and possibly causing a fire. We know this because ohms law I=V/R.

Types of current/circuits and how they are affected

So there are two types of current AC or alternating current and DC or direct current.

Power is measure in watts and the equation we need to know is P=IV very simple but very important. 

Resistance is very important in a circuit because if there is too little R than it might get to hot and cause a fire, but if there is too much resistance more energy will be required to the bulb brighter. There are four things that control the resistance, temp, width, length, and the type of wire.

And if the R increases then the I (current) will decrease and vise versa. 

There are also two different types of circuits, series and parallel. Series is wired so that if one appliance goes out they all go out, now this is helpful if you are wiring a fuse box because if one fuse over heats and cracks it'll stop the whole circuit and not allow for all the circuit to overheat and blow.

Parallel is much more sensible, and how all houses are wired, it allows appliances among other things to be turned off or unplugged and the rest of the appliances to work. This is possible because the appliances are on their own little circuit. 

In this diagram the circuit to the left is a series because the two bulbs are in the same circuit, the circuit to the right is a parallel circuit because the bulbs both have their own circuit. So if one was unscrewed the other would remain light, however this is not the case for the series (left) circuit.

So what happens to the total R as more appliances are added to the circuit? 

In a series circuit the R will increase but in a parallel circuit it will decrease.

What happens to the current as more appliances are added?

In series the current will decrease but in a parallel the current will increase.

What happens to the brightness as more appliances/bulbs are added?

In series they will get dimmer but in parallel they will all stay the same.

Calculate how much it will cost to run a 60watt light bulb connected to a 120V source continuously for 1 month if it costs .10 cents per kilowatt hour?

60 watt --> .06kW 730 hours in a month. 730x.06=43.80 43.80x.10=$4.38!!