Lecture Seven Physics 100 Fall 2012

Circuits part one

Exam 1 is Wednesday OCT 3, 2012

• You can use calculators!! • Materials up to and including this lecture is

covered.

Calculator/Homework System Comments

• OK, OK you can use calculators!! Just get your answers right! and practice using what I have been preaching (making estimates and doing math in your head) to check the answer the calculator spits out.

Homework System Comments

• Watch out for over rounding in the homework system. As written on the info sheet…always enter at least three non-zero digits for numbers less than one.

• For example, if your CALCULTOR gives you an answer of 0.000943432 DON’T enter 0.001 or even 0.00094. Enter 0.000943.

• You need to be correct to within 1%.• I will look for and override lost points associated

with this issue for this assignment.

Homework System Comments

• As stated on the syllabus, you get three extensions on homework. No questions asked. You can take them whenever you want. Just ask for them by using the link.

• You can look at previous homework assignments and previous answers.

Homework for next WednesdayAnswer the following question on a sheet of paper.

Is it approximately true that if you stood all the people in the world front to back, side by side that they would fit into the state of Rhode Island?

To answer:1. Estimate the area taken up by all the people in the world standing front to back, side to side in square feet.2. Get the area of Rhode Island from the internet and convert that to square feet.3. Compare.

Show all you work and state in words what you are doing.

You can work together but everyone has to submit their own paper.

Battery Vocabulary

Positive Terminal:the button end of the battery. Acts like there are excess positive charge there. It is marked +

Negative Terminal:the flat end of the battery. Acts like there are too many negative charges there. It is marked -

Light Bulb

Light bulbs also have two terminals:the side and the very bottom.

Filament wire

(both the horizontal and vertical parts)

Internal wiring of a bulb

Lighting a bulb• Here is one way to light a bulb with a single wire.

Draw 3 additional unique ways.

Internal wiring of a bulb makes sense.

Example circuit diagram

Circuit DiagramsLike a map, we use symbols to represent circuit elements

Vocabulary

• Insulator: A material through which electricity does not flow well.

• Conductor: A material through which electricity flows easily.

• Examples

Conductors and Insulators

• The electrons in a conductor are relatively free to move from one atom to the next.

• The electrons in an insulator are relatively immobile and don’t generally move between atoms.