For the past few weeks Physics regular has been studying Charges and Electricity. During this unit we explored:
-Charges and polarization (which included Coulomb's law)
-Electric Fields
-Electric Potential/Electric Potential Difference/Capacitors
-Ohm's Law
-Types of current, source of electrons, power
and
-Parallel and Series Circuits
The sections of this unit we discussed first were
charges, polarization, and Coulomb's law. Coulomb's law is an equation which
reads as follows F=k(q1 x q2/ d^2). The F in this equation represents force,
the K in this equation is a constant the q’s represent charges, which can be
negative or positive, the d refers to distance. The relationship between force
and distance is that when distance is doubled force is a fourth of what it was
previously. This section also included the transferring of electrons which we learned
using the question: why does a balloon stick to the wall once it has been
rubbed on your hair? I was unsure of what to expect of this 14 point problem,
but we went over it so much that I began to understand its point. The answer to
this question is that through friction, the balloon takes electrons from your
hair making it negatively charged. As the balloon gets closer to the wall, the
wall polarizes which means the protons in the wall are closer to the balloon
than the electrons in the wall (which we know because of Coulomb's law). This
just means that the protons in the wall have moved closer towards the electrons
and the electrons in the wall move farther away. The now polarized wall results
in the balloons ability to stick to it. Another question this unit was how lightning works and how lightning rods work? Lightning works by having negatively charged clouds that get
close to the ground. This negative charge polarizes the neutral earth and
brings the positive charges closest to the surface of the earth. When the
attractive force between these opposite charges gets to be too much a pathway
is formed from the cloud to the earth, and the charges rush to the earth creating
the flash which is followed by the sound. We use lightning rods to have
lightning strike the rods which are more conductive, then the charges travel
down a direct path to the Earth, rather than going through the house resulting
is little to no damage.
We
slowly moved on to studying electric fields, which are the area of influence
that a charged object has on other objects around it. They are generally shown
with vector arrows which indicate the charge moving within them. Positive
charges will have vectors which point outwards, thus repelling other positive
electrons. Negative charges will have vector arrows which point outward, thus
attracting positive electrons. During this section we encountered mainly large
scale problems which included: A positive charged particle finds itself in
an electric field. It moves to the left and increases velocity. Is the electric
field caused by a positive or negative charge? Many of my classmates and I were
tricked by this problem because we can’t know for sure. To answer this problem
we have to say that it could be either a positive or negative charge or a
combination of the two. Another question we encountered in this section was why
electronics are safe in a metal box, and that is because the metal casing works
as an electric shielding which causes the charges with the metal to rearrange
themselves so that there is no-net charge on the parts within. A Faraday cage is something (usually a metal casing) that
disperses charges equally around it so that any object inside will feel no
Net Force. This can be seen in computers or other valuable electronics that are
protected with a metal case. This is also referred to as Electric
Shielding.
In
the third section which was Potential difference, electric difference and
capacitors we explored voltage, current. Potential difference is just another name
for voltage, which is the difference of two currents. Electric potential is
very similar but instead it is just on current. A capacitor is a mechanism
that gives off a short, strong flash or discharge, this mechanism takes a
few moments to recharge. The major question of this section was: was why can
something with high voltage be less dangerous than something with less voltage?
If few charges with high voltage are being moved, they will not be as dangerous
as many charges with low voltages.
The fourth section of this unit focused on Ohms law, which states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality (the resistance) one arrives at the usual mathematical equation that describes this relationship: V=IR. voltage=(current*resistance).
The next section of unit 6 was types of current, source of electrons and power. The equation for power is Power=IV. This means power equals current times voltage. This equation and that of Ohm's law will be key in a few equations that will be seen in the near future.There
are two different types of current. They are AC (alternating current) and DC direct
current). An outlet in the wall gives out alternating and AA batteries give out
direct current. An outlet that gives out alternating current is commonly seen
with a block which converts AC to DC. The two types of circuits are series
or parallel. Series is when electronics are placed one after the other in
a circuit. This means that if one of the electronics stops working,
then the whole circuit will stop working. Parallel circuits are when each
electronic device has its own branch in a circuit. In a series,
the resistance adds, voltage adds, and current stays the same. In parallel,
resistance is cut in half, voltage will always be the same, and current adds.
The main question of this section was why does the circuit breaker in Lawrence
trip when girls are getting ready for prom? The simple reason is that Lawrence
is wired in a series so if one thing goes out all go out. The response that
gets you points is that Lawrence is wired in series so the more appliances
being used, the less power each one gets, and so when one stops working,
they all stop working. One thing we can use to prevent this is a fuse. A fuse regulates the amount of current going through a circuit. Fuses protect household appliances and the wiring of a
certain area. This works by having the conductor that bridges the two sides of
the fuse being rated for a certain current, when the current gets too high this
conductor melts and therefore switches the circuit off. Fuses are wired in
series so that when they melt, the whole circuit turns off. This protects
wiring as when current rises too high the wires start to combust which is
dangerous.
Unit Six was a whole section on energy and electricity. We
got to work with light bulbs and learned why a lot of things happened to us
like our hair standing up and how lightning worked. While this unit we did not
partake in making unit blog reflections we were able to cover an array of
topics which all related back to charges and electricity the unit topic and old
units. I still don’t understand the point of blog reflections, while for many
they help with studying I find them time consuming and hard to complete in the
time allotted. I spend most of my time shuffling through what I need to know
rather than reflecting on the unit as a whole.
For the most of this unit I sat in class confused on what we
were doing and missing class time due to games. Fortunately, I was able to make
up for lost notes but still not quite grasping concepts. For someone who missed class I’d say that my
effort improved because I asked questions and attempted to answer many
questions and participate in class. My problem solving skills varied based on
what the actually problem was but overall my problem solving skills I feel have
improved.
