UNIT - ELECTRICITY
In unit 6, we learned all about Electricity! The sub-topics we focused on were .......
- Charges/Polarization (Coulomb’s Law)
- Electric Fields
- Electric Potential/Electric Potential difference (capacitors)
- Ohm’s Law & Electric Potential difference
- Types of current
- Parallel and series circuits
Charges and Polarization including Coulomb's law —>
The first topic that we focused on in this unit was Charges and polarization. I thought that 'charge' was just the thing you did to your phone when it ran out of battery before this topic! In actuality, something becomes charged by having an extra amount or a lesser amount of protons or electrons (making it a negative or positive charge). The way that these objects become charged is through polarization. Something can become polar by friction or induction. An example of this is when you rub a balloon against your head and then attempt to stick it against the wall. I will give you an example of the correct way to answer this question fully
1) The balloon is charged by friction when it is rubbed against your head. When it is brought towards the wall, the wall polarizes. This means that all of the positive charges in the wall are drawn towars the negative charges in the balloon.
2) The positive charges in the wall move as close to the balloon as possible while all of the negative charges in the wall move away from the balloon
3) The distance between the opposite charges (attractive) is smaller than the distance between the like charges (repulsive).
4) F = kq1q1 / d2 : (Coulomb's Law) Since there is a greater distance between the repulsive forces, the force between then will be less than the attractive forces.
5) Therefore, the balloon will stick to the wall!
6) d F V.S. d F
Electric Fields --->
An electric field is defined as, "a region around a charged particle or object within a force would be exerted on other charged particles or others". This section was fairly straight-forward. We learned that if the arrows are pointing outwards on an electric field, the inside charge must be positive and that if the arrows were pointing inwards, the charge must be negative. The best problem that we used to justify electric fields was .... "Why is your computer safe inside a metal box?"
ANSWER:
We put out devices inside of a metal box to protect them from getting an electric shock and breaking. Charges build up on the corners of objects and if the object were to come in contact with something that could give it a shock, the wires and everything in it would get fried and it would be useless. When it is placed inside a metal box, it is safe. This is because when the charges land on the metal box, the metal displaces them and they all become neutral, keeping the device from having a charge and possible breaking
Electric Potential/Electric Potential difference (capacitors) --->
Electric potential/electric potential difference was all to do with volt/voltage/and flash inside of a camera. Most people get confused between the difference of a volt and voltage.....
VOLT= electric potential ( PE/q or J/C )
VOLTAGE = the difference in electric potential. Voltage causes current.
ELECTRIC POTENTIAL = potential energy/charge
ELECTRIC POTENTIAL ENERGY = the stored energy between electric charges in electric fields
A flash is an example of a capacitor. Explain why you can’t use your flash continuously and by doing so explain how capacitors work
A camera has 2 oppositely charged plates inside of it. These two plates and not connected. You add charges to each plate thus increasing the Force and energy of the electric field between the plates. WHen you briefly connect the plates (push the button on your camera to take a picture) energy rushes from one plate to the next and a light in produced (flash). You cannot use flash continuously because you need to give the charges time to build up enough to create light.
Ohm’s Law & Electric Potential difference --->
"Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points." In our class, we learned that ohm's law deals with the relation to distance and we used the formula F = kq1q2/d2. The question of, "Why are the wingspans of birds a consideration in determining the spacing between parallel wires in power lines?" is a good one to help fully understand electric potential difference.
ANSWER:
When a bird lands on a wire, it does not get a shock because it is not completing a full circuit. Power-line-maker people are technically not allowed to put power lines close enough together so that a bird would be able to touch both of them. Two power lines next to each other would have a huge difference in voltage. Therefore, if a bird were you touch one line with one wing, and another line with its other wing, it would complete a circuit and a current would run through the bird. This could be detrimental to the bird, very likely causing it to die.
This is also the section where we learned about resistance and the formula for it. To calculate resistance we use I = V/R. So in a question like "You plug a 4A radio into a 240V circuit. What is the resistance of the radio?" we would answer it like this
4 = 240v / R
Multiply both sides by R
4R = 240
Divide both sides by 4
R= 60 ohms of resistance (Ω)
Types of Current, source of electrons, Power --->
There are two types of current, alternating current (AC) and direct current (DC). *We learned a pretty cool dance in class for this, you can see me after class if you want to see it*
Parallel and series circuits --->
There are two types of circuits that we focused on in this section. We learned that each circuit reacts very differently.
Series :
- When more appliances are added to the series circuit, the total resistance goes up.
- When more appliances are added to the series circuit, the total current goes down.
- When more appliances are added to the series circuit, the total brightness goes down.
- When one of the lightbulbs is removed or stops working, the entire system of lightbulbs will go out
Parallel :
- When more appliances are added to the series circuit, the total resistance goes down.
- When more appliances are added to the series circuit, the total current goes up.
- When more appliances are added to the series circuit, the total brightness stays the same
- When one of the lightbulbs is removed or stops working, the rest of the system and lightbulbs stay on
