Unit 6

Electricity and how we use it

Current

Conductor

Insulator


There are three ways to charge an object:

Induction- A charged object moves toward a neutral object. The like charges in both objects repel and so these charges in the neutral object separate and are polarized. The opposite charges in both objects move closer together and need to find the path of least resistance to eachother. The object is thus polarized and charged.
Friction- objects rub together to make charge. "electrons are borrowed"

Direct contact- things give eachother charge by touching directly

There are positive and negative charges. Electrons are negative and Protons are positive. Say an object has more of on or the other, then the one that it has most is the overall charge of the object. Negative charges repel eachother and positive charges repel eachother. But negative and positive charges attract.

Scientists are not so sure what causes lighting. But they do know how it works. Lighting is just a giant version of Induction. The clouds have charges and the ground has charges. Positive charges attract the negative charges in the ground. The cloud and ground are polarized and the like charges need to find the path of least resistance to the ground. The charges then "jump" accross the space- creating a flash of electric current called lighting. Lightning rods on houses help the lighting find the path of least resistance (because the rods are straight and are directly connected to the ground) so that the lighting will not pass through the house or building but will pass through the rod instead.

Coulombs law- distance is inversely proportional to the force between objects F= K q1 q2/ d squared



electric feilds
E= F/q
We usually talk about how the positive charges effect this field
Arrows show us how the field will affect a positive charge. Inward arrows say that the feild is negatively charged and outward arrows say that the feild is positively charged. Arrows that are far from the center of the field or that are farther apart from eachother show a weak field.

Voltage- The electric potential energy difference.  (difference between two points). (measured in volts).We also use it to measure how much energy is available out of one Coulumb of charge.
If there is a large difference in charge, then there is a large difference in potential energy. Which means that there is a large difference in Kinetic Energy since PE=KE.
V= change in PE/ q

Ohms law-shows the relationship between voltage and current through the use of resistance.

Resistance is a force that slows down the current and makes it weaker. If the voltage is stronger then the current is stronger, which would mean that the resistance is lower. Resistance is inversely proportional to current and voltage. Voltage and Current are directly proportional to eachother. The equation is I= V/R.
Ways of manipulating resistance: To make it more resitance -->
 Lengthen the filament in the light bulb or make it a thinner filament. Resistance is also measured in ohms.

Currents- The flow of charges through an object. It is measured in amperes. There are two types. Direct current and Alternating Current. We use both in society.
DC- Direct Current. (Charges only flow in one direction) hint: used in batteries.
AC- Alternating Current (charges flow and change in opposite directions). We manipulate Alternating Current by alternating the polarity of the voltage. AC is used in common household appliances.

Capacitors- smooth out the current that is used. They have electrically charged plates that build up electric charge by passing electrons between them.
Electric Power- the rate in which electric energy can be converted
Power= energy/time
Power-= current times voltage
series and parallel circuits are used in electric power. Series is just one loop while Parallel has two loops of cuircuits connected to eachother. We learned that if we added more appliances to a series circuit, the resistance would increase and so we dont use series if we are  in need of the use of multiple appliances. Now Parallel works just the opposite: as we increase appliances, current increases and therefore voltage increases. And because they are inversely proportional to resistance: resistance decreases.

Fuses- When the current becomes too hot, a fuse melts and stops the current from blowing a circuit and prevents the circuit from turning into an electrical fire. The fuse can be inserted anywhere within a series circuit but must be inserted into the series part of the parallel circuit in order to be able to block dangerous heat from causing a fire in the parallel circuit.


This unit, at first, proved pretty difficult.  I had trouble on the test and some difficulty understanding what was being asked of me in the quizes. Homework seemed a bit confusing as well. But when I took the time to understand it and write a blog post- I found it pretty straight forward. Thanks Mr. Rue!