Electricity
Circuits are crazy. Here’s a simplified rundown of what goes on inside one of them
1. A current it formed when there is a net movement of electrons (displacement). If an electron moves 5um to the left and 5um to the right there is no current. When there is a displacement, there will be a drift velocity (displacement/time). We call this a current and use a slightly different equation than the kinematics equation. Current (I) = Q (charge)/ time). Don’t forget that Q = n(e).
2. If you’ll remember, a charge will move due to a potential difference. A positive charge will move from high to low potential and a negative charge will move from a low potential to a high potential. With this in mind, a current (movement of electrons) will occur when a potential (voltage) is applied. This voltage is sometimes called an electromotive force (EMF).
3a. Resistance: Any object that causes opposition to a current. In the picture above, you can see that a resistor decreases the current. The arrows signify the movement of electrons from a region of low potential to high potential. Resistance can be determined using Ohm’s Law - V=(I)(R) or R = V/I.
3b. Internal Resistance: Resistance is also an intrinsic property of the object conducting the electrons. It depends on both an experimentally determined constant, the area and the length. R = p(L/A). As the length of the wire increases, so does the resistance. As the area of the wire increases, the resistance decreases. A good analogy to this is a drinking straw. If you have a habit of biting the tip of your straw, you know that it becoming increasingly difficult to suck up the liquid. This is because the area is DECREASING. Similarly, if you have one of those crazy straws that are really long, it requires more suction to get the liquid through the entire straw. Hence, as length increases, so does the resistance.
Coming soon: Circuits
