Park Physics with Sean Lally - 2017-2018

1. Consider 3 light bulbs, with equal resistance (30 ohms each).  They are connected to a 9-V battery. A.  Where will the total resistance of the circuit be greatest - if the bulbs are in series, parallel, or is it the same in both cases? B.   Where will the bulbs "kill" the battery soonest - if the bulbs are in series, parallel, or is it the same in both cases? C.  Full out complete tables for both cases:  when the bulbs are in series and when they are in parallel. 2.  Repeat 1C above for the case of 2 resistors (30 and 60 ohms) with a 120-V battery.  Determine everything we care about for the series and parallel cases. More practice can be created here: https://www.explorelearning.com/index.cfm?method=cResource.dspDetail&resourceID=398 Launch the "gizmo" (click on the picture) and build circuits by clicking and dragging components.  You can then drag an ammeter onto the wire and it will give you the current.  You can also drag a voltm

Series: 4 resistors (1, 2, 3, 4 ohms) are in series with a 50-V power supply.  Find: - total resistance - total current - all voltages Draw a schematic for this problem, too. Parallel: 3 resistors (5, 10, 15 ohms) are in parallel with a 30-V power supply.  Find: - voltages - currents - total current - total resistance Draw a schematic for this problem, too.

Answers are at the bottom. 1.  Consider 2 resistors (6 and 12 ohms) in parallel with a 24-V battery.  Find the following: - schematic for the circuit - voltage and current for each resistor - total resistance for the circuit  2.  Consider 3 resistors (2, 4, 8 ohms) in parallel with a 48-V battery.  Find the following: - schematic -voltage and current for each resistor - total resistance Answers: 1.  24-V for each; 4 and 2 A; 4 ohms total 2.  48-V for each; 24, 12, and 6 A; 48/42 = 1.14 ohms

1.  The total resistance of resistors in series is their sum. R Total = R 1 + R 2 + … 2.  Current in a circuit is constant from the battery.  If resistors are in series, they all have the same current as the battery delivers.  Calculate this by: I = V/R 3.  The resistor voltages in a series circuit add up to the total battery voltage. Example problem from class: R1 = 1 ohm R2 = 2 ohms R3 = 3 ohms If all 3 resistors are in series with a 12-V battery, the total current is 2-A.  The individual resistor voltages are:  2-V, 4-V, and 6-V.  Note that these add to 12-V. Try this problem: 3 resistors (4, 5, and 3 ohms) in series with 36-V.  Find the following: - total resistance of the circuit - current through each resistor - voltage over each resistor

Circuit questions to TURN IN ON FRIDAY (in class) 1.  Describe the difference between voltage, current, and resistance.  Give the proper units, too. 2.  What is the resistance of a light bulb that allows 2 A of current through it when connected to a 12-V battery? 3.  A 5-ohm resistor is connected to a 10-volt battery. What current goes through the resistor? 4.  You have 2 bulbs in series (one right after the other) - remove one (unscrew it) and what happens to the brightness of both bulbs?  (See picture below.) 5.  You have 2 bulbs in parallel (both connected to the same voltage source) - remove one (unscrew) and what happens to the brightness of both bulbs?  (See picture below.) 6.  Draw a schematic for 2 resistors in series with a battery and switch, using the correct symbols. 7.  Recall the recent mini-lab we completed where we compared current to resistance.  Draw an approximate graph of current vs. resistance, assuming that the voltage is held constant (as it was in

Be prepared to start building your structure this Wednesday - 1-17-18. Bring any materials you will need for building.

Folks - so sorry to be out sick today.  Here's what I'd like you to do. First, compare your definitions of current and resistance at your table.  Then read mine and take notes. After this, you may work (with your partner, if you have one) on the electrical structure project.   I'll be available during lunch tomorrow for anyone who needs to meet.  I'll also check email throughout the day. Thanks. // Circuits 1 Thus far, we have only discussed "static" (stationary) charges.  Static charges alone are useful, but not nearly as much as charges in motion.  As you recall, electrons are the most easily moved particles.  However, for sake of ease in sign convention (positive vs. negative), we define the following: Current  (I) - the rate at which positive charge "flows" I = Q/t The unit is the coulomb per second, defined as an  ampere  (A).  Just as one coulomb is a huge amount of charge (nearly 6.3 billion billion protons), one ampere (or amp) is a tremendou

Make sure that you recorded today's definition of voltage. Next, read up a little about the definitions of these two concepts.  Bring a brief definition, and ideally, something else in your own words. - current - resistance Happy New Year, physics phriends!