Electric Circuits

C Block finished up the last bit of Chapter 19 material today, which focused on electrical power. Remember that power is a rate function and can be approached from the angle of rate of energy conversion or rate of work being done. We looked at the consequences of delivering a specified power at high current or high voltage and how those delivery methods impacted how much power was dissipated purely as heat. Make sure you understand I²R loss or Joule heating and why that is not appropriate for many applications. That's why power companies minimize the problem by delivering power at high voltages and reducing the amount of usable energy lost to heat.

B Block started in with electric circuits today. Folks examined the nature of circuits, the role of switches, the consequences of a short circuit and the value of using a schematic diagram. Tomorrow, we'll examine a specific type of circuit - the series circuit - and how to analyze its function using Ohm's Law and the circuit's equivalent resistance. That's what E Block did in class today. Series circuits force charges to pass through every load in sequence and no load may be skipped. A problem with a load can cause the entire circuit to open so no load functions. For series circuits, therefore, the resistance charges experience is the sum of every individual resistance for the loads. The R_eq is larger than the value of the largest resistance in the circuit. Also, since charges cannot pile up in the circuit, they must flow at the same rate through the entire circuit, so the current through each load is identical. However, charges must use different amounts of energy to achieve this rate of motion as they pass through loads of varying resistances. The potential difference across each load will differ and reflect this property of series circuits. Tomorrow - parallel circuits!

F Block conducted their lab on Ohm's Law, examining ohmic resistors, a non-ohmic light bulb and an LED. The resistors demonstrated a nice linear relationship when V and I were measured and graphed, with the slope of the line being the value of the resistor. The light bulb showed different levels of resistance at different voltages and the LED permitted charge flow in a single direction only. Diodes function to direct charge motion, but resistors function to set the value for current. We'll explore this more when we move through the Circuits chapter, which starts tomorrow.