- Discuss the differences between seriesand parallel circuits

- Conclude our hands-on study of electricity with construction of more complex circuits

TODAY’S OUTCOMES:

ELECTRICITY

SUN AND MOON- Introduce and discuss moon observation project and individual responsibilities

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/moonTime and Date AS: http://timeanddate.com/worldclock/moonrise.htmlUsually, 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 yourobservation on a whiteboard for the class to see.

3) The whole class adds the observation to their logbook.

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)

9-6-11 7:30pm

45°W

sample (not real data)

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

Your first moon observation assignment willbe 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!

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 staysthe same .

> 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?

> 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 lightbulbs are turned on. If more bulbs are lit, with the samebrightness, then more current flows from the powersource, and POWER increases with CURRENT.

CURRENT IN SERIES CIRCUITS3 volts

(assume all bulbs are identical)

A

BC

D

Currents through A, B, C, and D are all equalCurrents through E, F, G, H and J are all equal

Currents in the left diagram are GREATER THAN the currents in the right diagram

1) Current is the same at all points in a SERIES circuit.

2) Adding more devices/bulbs in SERIES reduces the current.

3 voltsE

F

G

H

J

Bulbs dimmerin right diagram

CURRENT IN PARALLEL CIRCUITS3 volts

(assume all bulbs are identical)

A

B

C

D

Currents through A, B, C, and D are NOT all equal

Currents through E, F, G, H and J are NOT all equal

Bulbs are (almost)the same

brightness in both diagrams

3 voltsE

F

G

J

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

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

CURRENT IN PARALLEL CIRCUITS3 volts

(assume all bulbs are identical)

A

B

C

D

3 voltsE

F

G

J

Bulbs are (almost)the same

brightness in both diagrams

H

1) Current is NOT the same at all points in a PARALLEL circuit, and is highest in the wiresleading 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. 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.

- 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:

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.

TEST ON ELECTRICITY:OPEN NOTE

NEXT WEDNESDAY 2/1/12

TODAY IS THE LAST ELECTRICAL CIRCUIT LAB

- Discuss the differences between seriesand parallel circuits✓

- Conclude our hands-on study of electricity with construction of more complex circuits

TODAY’S OUTCOMES:

ELECTRICITY

SUN AND MOON- Introduce and discuss moon observation project and individual responsibilities✓