Wednesday April 9t

Conventional current is the flow of positive charge. The charge flows from postive to Negative. However, in reality electrons are being flowing in the oppositive direction. Electronn current is when electrons (or the negative charge) are flowing from positive to negative. The Right Hand Rule is important because it shows the direction of the magnetic field aoudn a current carrying conductor. By putting your thumb upright, is shows the currents direction. The direction that the fingers curl show the direction of the magnetic field. The concentric cirlces of the magnetic field aorund a current carrying wire can be labeled with dots or crosses. Solenoids is the wire wound as a helix around a metallic core. When an electrical current is passed through it, it creates a magnetic field. A bar magnet is similiar to the field shape of a solenoid madnetic field. The field can increase with greater current, more turns of wire, and soft iron core. When using the right hand rule for a solenoid, the thumb must point to the north pole.

Wimshurst Machine

This machine creates electric charges through electrostatic induction and is used to generate high voltages. It was develeped between 1880 and 1883 by a British inventor by the name of James Wimshurst. This machine consists of two insulated disks and their metal sectors which rotate in opposite directions. This movement creates an imbalance of charges which is amplified and collected by two pairs of metal combs. These combs have points placed near the surfaces of each disk and are mounted on insulated supports. These are then connected to the output terminals. If everything goes as planned you will see a spark jump across the gap.

Tuesday April 1st

Today we started out the day by going over our homework from last night. (it was that packet with all the different circuits) A few things to remember is to watch out for when it is K-ohms. It is a good review, definately worth doing if you haven't already. We then started with notes. It was pretty much a review of yesterdays lesson. See Pauls post if you missed Monday! We worked on a practice worksheet as well. It was helpful because it helped to reinforce and actually see these rules applied. A few things to note when drawing circuits. Be careful as to where you place the Ammeter. Be sure to place it where you get the full currect and not between where the current may be split. You can use your reference table to help you with the signs that need to be used. Also another thing from the Practice Worksheet always look at the different options you have to equations.
We also learned about meters in circuits.
A voltmeter: It is connected in a parallel circuit and it is intended to measure potential difference between two positions in a circuit. It has an extremely high internal resistance which means it won't let much current through.
A Ammeter: It measures current through a single point in a circuit. It has an extremely low internal resistance which creates an extremely small voltage drop.
There was no homework assigned today. There is a test Monday, I suggest doing the review packets.

Today we analyzed circuits, learning primarily about equivalent resistance, which is always measured from the source. The equation is R=V/I. There are two primary types of circuits, series and parallel. Series circuits have only one path for the current to travel, with many drops of potential along the way. Here is picture of a series circuit:

The current in a series circuit is the same throughout, and the sum of the potential drops is equal to the source potential. In this type of circuit, resistance is measured as the sum of the resistance of its components. On the other hand, parallel circuits have only one potential drop because there are multiple paths for the current to flow. In this case, total current is measured by the sum of the branch currents, which is equal to the current supplied by the source. Here is a picture of a parallel circuit:


As in a series circuit, resistance in a parallel circuit is measured as the sum of the resistance of its branch resistors, however the reciprocal must be taken in this case. That just about wraps up today’s lesson, peace.

3/26

Today we learned about circuits and currents.

We learned the difference between an alternating current and direct current which is self explanitory by the name

We learned what a current was, the flow of electric charge, and that the symbol was I. The unit of charge is an Ampere or Amp.

Resistance is the opposition to current flow and is represented by the symbol R. Its unit is the Ohm.

Ohm's Law-At constant temperature, the current in a metallic conductor is directly proportional to the potential difference between its ends.

Ohm's law has a few equations such as R=V/I, I=V/R, and V=IR

3/28/08 Circuits Blog

Equivalent Resistance = V/I

Ohm's Law applies to the circuit as a whole, and to each individual resistor. We can build circuits in several different configurations. The current flow can branch out and back in.

Tuesday, March 25, 2008

Today we started off writing sentences that accuratley incorporate the word circuit. We then went to notes where we learned about circuits. An electrical circuit is a closed loop or path through which charged particles can travel through. A closed electrical circuit allows for an electrical current to form. An electrical current is formed by a source of potential differences and includes one or more resistances.

We then learned about how water is analagous to electrical flow. We also watched a video on electrical flow. This video mentioned how the invention of the battery revolutionized technology and eventually led to Thomas Edison to develop electricity lamp.

Then we learned about circuit elements. Circuit elements include:

Source elements, which produce a potential difference

Load elements, which is a device that the source is connected to

Control elements, that controls the flow of electric current such as a switch

We also learned some new terms such as Current (I) which is the flow of electric charges. It is also the time-rate at which charge flows past a given point in a circuit. We found out that other electrical terms and equations are in our reference tables. The equation I= the change in charge (q)/ time(t).