Current and Resistance Onward

B Block was introduced to the concept of electrical resistance through a lab on Ohm's Law. For some substances, the ratio of potential difference to current is fixed and the proportionality constant is the resistance of the system. Not all substances follow this relationship for all potential differences and these substances, like light bulb filaments, are termed non-ohmic. You found that the slopes of the lines for the resistors were close to the stated resistance values, and the light bulb showed two resistances, one at low voltages and another at higher values. Folks also tested an LED and a Zener diode to see their how they played in the current/voltage pool and found that current flowed in one direction. Diodes can be thought of as valves, permitting current flow in one direction. The Zener diode, however, did let current flow when you crested 5V. Zener diodes have a breakdown voltage that will allow the release of current above a certain value, without damaging the component. Standard diodes can be damaged if current is forced backwards. Tomorrow, we'll discuss the nature of resistance, factors that affect an object's resistance and dip our toes into the topic of superconductivity, where zero resistance can be reached when we dip below a certain critical temperature.

That last part was the focus of E-Blocks's work today. We defined resistance and looked at factors (length, diameter, temperature and identity of material) that impact an object's resistance. Make sure you know specifically how these factors affect resistance and be able to compare objects resistances based on their construction. We took on Ohm's Law, which sets the resistance value for a substance based on the ratio of supplied potential difference and observed current flow, and contrasted ohmic and non-ohmic substances. We then looked at the absence of resistance for the topic of superconductivity and some possible applications if we can only make superconductivity a financially-viable option for large-scale use. Tomorrow - electric power!

C Block reviewed their Ohm's Law lab then had time to work on test corrections. F Block started their journey into electric current through defining current, looking at the concept of conventional current and direction of charge-carrier motion and discussing why the actual velocity of charges in a system is much lower than we would predict. We ended by contrasting alternating and direct current and discussing examples of where each is used. Tomorrow, we add the property of resistance to our electricity grab bag and one new formula - Ohm's Law.