Charges and Polarization including Coulomb's law:
Beginning our unit we started off learning about charges and polarization. Charges can be transferred from one object to another in three different ways: contact, friction, and induction.
Contact: when someone is positively charged and they touch a negative person, causing a shock when the charges transfer.
Friction: Rubbing positively charged particles against negatively charged particles causing them to transfer.
Induction:
a) The metallic sphere is neutral (same number of protons and electrons)
b) A negatively charged rod comes close to the sphere, causing the charges within the sphere to separate (sphere is still neutral)
c) One side of the sphere is grounded, so the negative charges equalize with the ground, leaving that side of the sphere neutral, but the other side still positive (the sphere is now charged)
d) The connection to the ground is removed (sphere is still charged)
e) The rod is removed and the positive charges disperse throughout the sphere (sphere is still charged)
Being "polar" means that the charges have been separated. The object that has been polarized no longer has a charge, but instead is now neutral.
Sooo….. How does a balloon stick to the wall without tape?
1. Balloon takes charges from hair (becomes negative)
2. balloon charges by friction
3. the wall polarizes when the negatively charged balloon comes near it
4. positive charges move closer to the balloon, negative charges move father away. (opposites attract)
5. the distance between opposite attractive charges is less then the distance between the like repulsive charges
6. the attractive force is greater than repulsive force because of Coulomb's Law: F=kq1q2
7. larger attractive force = balloon sticks to wall d^2
Electric Fields:
The area around charge that can influence another charge is an electric field.
The closer the lines are, the stronger the electric field. To the right is a picture of which direction the electric charge is going for both positive and negative electrons.
The formula for the strength of an electric field is: E = f/q
Electric shielding is when an object inside the metal casing is protected so that whenever there is a charge that could effect the object inside the casing, the metal is used as a shield and protects from the charge, keeping the objects charge at zero always, and making sure the object feels no force.
Electric Potential/Electric Potential difference, Capacitors:
Voltage is the same thing as potential potential.
V = change in PE/q (units of Volts = V)
If two like charges were pushed together, they will repel and the electric potential energy will increase
Birds, when standing on a wire don't get hurt because the bird is not experiencing potential difference between its feet, therefore no current flows. However, if the bird makes contact with the two different wires, it would be connecting a circuit with a potential difference (voltage) and current would flow through the bird.
Flashes can't work continuous because once the flash flashes, the charges, much like capacitors, must recharge in order to flash again, depending on size, the charge recharges faster if smaller.
Power, Resistance:
Electric Fields:
The area around charge that can influence another charge is an electric field.
The formula for the strength of an electric field is: E = f/q
Electric shielding is when an object inside the metal casing is protected so that whenever there is a charge that could effect the object inside the casing, the metal is used as a shield and protects from the charge, keeping the objects charge at zero always, and making sure the object feels no force.
Electric Potential/Electric Potential difference, Capacitors:
Voltage is the same thing as potential potential.
V = change in PE/q (units of Volts = V)
If two like charges were pushed together, they will repel and the electric potential energy will increase
Birds, when standing on a wire don't get hurt because the bird is not experiencing potential difference between its feet, therefore no current flows. However, if the bird makes contact with the two different wires, it would be connecting a circuit with a potential difference (voltage) and current would flow through the bird.
Flashes can't work continuous because once the flash flashes, the charges, much like capacitors, must recharge in order to flash again, depending on size, the charge recharges faster if smaller.
Power, Resistance:
Current is the flow of charges (units: Amps (A) goes through the circuit)
Resistance (Ohms) simply resists the flow of charges. Making a wire thinner, or longer will increase the resistance.
Ohm's Law --> V = IR
Power formulae --> Power = VI
Series circuits are wires in such a way that all the electrical devices are connected along a single wire, such that the same electric current exists in all of them.
Parallel circuits are wired so that the same voltage acts across each one, but a break in any one path does not interrupt the flow of charges in the other paths.
If a light bulb in the series circuit were to go out, then not the lights would go out because their current is connected. If a build in the parallel circuit were to go out, then, because their currents re not connects, the one build would go out, but the other on would stay on. With series, the more appliances added, the dimmer the light will be, but parallel's lights will stay the same.
Fuse breakers keep homes, which as wired in parallel, from burning. Because homes are wired parallel, the more appliances plugged in, the greater the current drawn. When a wire heats up because of the amount of current, it can blow. So a circuit breaker is there wired in series with the rest of the circuit to make sure everything goes off to keep it from blowing.
What I found difficult and how I over came that:
This unit I found potential difference very difficauly, and it took some ONKs and discussing it with my table, but when I was studying for a quiz one night and the answers to the ONK we had taken a few days before was online, I was reading the correct answers and finally got it when it was compared to a bird standing on wires. This was how I saw it and how it just clicked.
A few times I had to stick with the problem, even thought it was difficult, and when in class, I would ask questions until I understood how to do it correctly and why I had done it wrong.
My goals next unit are to not wait till half way into the unit to realize that I had been zoning out the entire time. Keeping up will save me in the long run.
In my room I saw an example of a series circuit I have a power source where I plug everything in, and now I understand why it is so energy consuming: It takes more current to run all the appliances, and therefore, drains energy.
Resistance (Ohms) simply resists the flow of charges. Making a wire thinner, or longer will increase the resistance.
Ohm's Law --> V = IR
Power formulae --> Power = VI
Parallel and Series Circuits:
Parallel circuits are wired so that the same voltage acts across each one, but a break in any one path does not interrupt the flow of charges in the other paths.
If a light bulb in the series circuit were to go out, then not the lights would go out because their current is connected. If a build in the parallel circuit were to go out, then, because their currents re not connects, the one build would go out, but the other on would stay on. With series, the more appliances added, the dimmer the light will be, but parallel's lights will stay the same.
Fuse breakers keep homes, which as wired in parallel, from burning. Because homes are wired parallel, the more appliances plugged in, the greater the current drawn. When a wire heats up because of the amount of current, it can blow. So a circuit breaker is there wired in series with the rest of the circuit to make sure everything goes off to keep it from blowing. What I found difficult and how I over came that:
This unit I found potential difference very difficauly, and it took some ONKs and discussing it with my table, but when I was studying for a quiz one night and the answers to the ONK we had taken a few days before was online, I was reading the correct answers and finally got it when it was compared to a bird standing on wires. This was how I saw it and how it just clicked.
A few times I had to stick with the problem, even thought it was difficult, and when in class, I would ask questions until I understood how to do it correctly and why I had done it wrong.
My goals next unit are to not wait till half way into the unit to realize that I had been zoning out the entire time. Keeping up will save me in the long run.
In my room I saw an example of a series circuit I have a power source where I plug everything in, and now I understand why it is so energy consuming: It takes more current to run all the appliances, and therefore, drains energy.
