TODAY’S OUTCOMES: SUN AND MOON ELECTRICITY - Introduce and discuss moon observation project and individual responsibilities - Discuss the differences between series and parallel circuits - Conclude our hands-on study of electricity with construction of more complex circuits ELECTRICITY

HOW DO I MAKE A MOON OBSERVATION? 1) Check the weather! Make sure it’s feasible to look for the moon. 2) Check moonrise and moonset times! Some resources: Farmers’ Almanac: http://www.almanac.com/moon Time and Date AS: http://timeanddate.com/worldclock/moonrise.html Usually, the moon is easiest to see midway between moonrise and set - except when it’s a slim crescent - then near sunrise or sunset is a better bet. 3) Be persistent! - Sometimes (esp. during the day) it can take a while to spot the moon....

HOW DO I RECORD A MOON OBSERVATION? 1) Submit it on Blackboard - you will be asked to pick which image (from a set) currently resembles the moon, the date & time, and angle & direction to the sun (if daylight) 2) You may be asked in class to duplicate your observation on a whiteboard for the class to see. 3) The whole class adds the observation to their logbook. 3) Be persistent! - Sometimes (esp. during the day) it can take a while to spot the moon....

If we can’t make an observation on a given day, put an “X” on it Each entry must have: -date and time of the observation -circle representing the moon, with the dark part shaded -IF NOT LATE AT NIGHT, the following info on the sun: - An arrow pointing the general direction of the sun - Whether the sun is east or west of the moon - The arc measurement in degrees between the sun and moon (see bottom of your handout) Start (right now) by filling out a date on every square through the end of Feb., starting with today! If we can’t make an observation on a given day, put an “X” on it 9-6-11 7:30pm 45°W sample (not real data)

Your first moon observation assignment will be given today online. You will be asked to: 1) Find the moonrise and moonset times for every day of the next week, and answer a couple simple questions about them. 2) You will be required to make and submit at least one moon observation over the next 7 days. Your logbook must be updated every class session until it is collected later in the semester! 3) Be persistent! - Sometimes (esp. during the day) it can take a while to spot the moon....

> The circuit for the lights in a house resembles the circuit drawn at right. The bulbs are all in parallel. What are the advantages of wiring them this way, instead of putting them in series? 1) In a series circuit, if one electrical device (bulb) is turned off, ALL the devices (bulbs) go off, because the circuit is broken - this would not be good in a house! 2) In a series circuit, the brightest of the bulbs depends on the number of bulbs, but in a parallel circuit the brightness stays the same . > Terry claims there is another advantage: the additional light bulbs don’t cost anything to operate. He argues that the light bulbs are independent of each other, and so there is no way for the power company to know how many are turned on. Paula says there is a way for the power company to tell when a light bulb is turned on. Please explain who is right. Paula is correct - the power used is higher if more light bulbs are turned on. If more bulbs are lit, with the same brightness, then more current flows from the power source, and POWER increases with CURRENT.

CURRENT IN SERIES CIRCUITS (assume all bulbs are identical) 3 volts 3 volts E F G H J Bulbs dimmer in right diagram D A B C Currents through A, B, C, and D are all equal Currents through E, F, G, H and J are all equal 1) Current is the same at all points in a SERIES circuit. Currents in the left diagram are GREATER THAN the currents in the right diagram 2) Adding more devices/bulbs in SERIES reduces the current.

CURRENT IN PARALLEL CIRCUITS (assume all bulbs are identical) 3 volts Bulbs are (almost) the same brightness in both diagrams 3 volts E F G J H D A The current through E or J is the SUM of the currents through F, G, H Current E = Current J = Current F + Current G + Current H The current splits at the green points ; so the current through A or D is the SUM of the currents through B and C Current A = Current D = Current B + Current C B C Currents through A, B, C, and D are NOT all equal Currents through E, F, G, H and J are NOT all equal

CURRENT IN PARALLEL CIRCUITS the same brightness in both diagrams (assume all bulbs are identical) 3 volts 3 volts D A J E Bulbs are (almost) the same brightness in both diagrams B F G C H 1) Current is NOT the same at all points in a PARALLEL circuit, and is highest in the wires leading to and from the power source 2) Adding more devices/bulbs in PARALLEL increases the current at the power source.

9. Susan made an extra bright flashlight 9. Susan made an extra bright flashlight. It has two batteries (like most flashlights) but three light bulbs. It gives off three times as much light, but the batteries don't last very long. Here is a diagram of Susan's flashlight. Explain how the concepts voltage, current, power, and energy are involved in this device; by the time you are done, you should have completely explained the sentence, " It gives off three times as much light, but the batteries don't last very long. " Adding extra bulbs in parallel to a common voltage increases the current drawn from the batteries, and thus the power used, which increases total brightness. A higher power flashlight increases the rate at which energy is used, depleting the batteries faster.

WHAT YOU ARE EXPECTED TO KNOW: - How series and parallel circuits are different - What happens in a parallel circuit when more elements are added - Where the current is greatest in a parallel circuit and why WHAT YOU ARE EXPECTED TO KNOW:

TODAY IS THE LAST ELECTRICAL CIRCUIT LAB TEST ON ELECTRICITY: OPEN NOTE NEXT WEDNESDAY 2/1/12 Homework Assignments: 1) Online: Moon Observations - due next Fri. 2) Written: Review sheet - due next Wed. (some answers are already posted on Blackboard!) 3) Reading: Electrical safety - by Mon.

TODAY’S OUTCOMES: SUN AND MOON ELECTRICITY - Introduce and discuss moon observation project and individual responsibilities✓ - Discuss the differences between series and parallel circuits✓ - Conclude our hands-on study of electricity with construction of more complex circuits ELECTRICITY