Electrical CircuitsProf. Jennifer M. Blain Christen

BioElectric Systems and Technology

Leadership in Engineering

James West

George Carruthers

Patricia Bath

Units and Scaling

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/

http://www.youtube.com/watch?v=A2cmlhfdxuY

Units and Scaling

Pico- 10-12

Nano- 10-9

Micro- 10-6

Milli- 10-3

Centi- 10-2

(none) 100

kilo- 103

Mega 106

Giga 109

Tera 1012

Units and Scaling

What units do we use these words with?

Meters length

Liters volume

Grams mass

Seconds time

Volts voltageAmps currentWatts powerOhms resistance

Resistance

Opposition to the flow of charge.

When we measure resistance, we measure how much an object “resists” the electrons moving through it.

We measure resistance in Ohms.

We abbreviate this with an Omega, written like this .

Resistance

Conductors have low resistance.

Insulators have high resistance.

Some things are in the middle, like silicon. Silicon is a semiconductor.

We draw symbols for resistors that look like…

Resistance

We can find out the resistance of an object with this formula:

R = x L

WxH

How can we measure resistance?

m200

1.5V9V

Ohms

Range

Sometimes, you try to measure something too big for me. I don’t know what to do, so I show you this.

Try changing the range. If you are up to 2000k, and still get this…sorry!

Let’s try it out!

You have 4 resistors.

Write down the value of each one.

Keep them separated, you need to know which one you are using!

Battery

This is a 9 volt battery. Let’s check to see if it’s really 9 volts.

We draw symbols for batteries that look like… or

How can we measure voltage?

m200

1.5V9V

Volts

Range

Let’s make a circuit

This is a breadboard. We use it to easily make electrical connections.

Hidden inside are electrical connections. The connections are made between each group of 5 holes. Like this…

Let’s check and make sure I’m not full of it.

Turn the dial here, see what it says.

We are going to use wires.

Remember, wires are conductors inside of insulators. We can use them to connect two things together.

conductor

insulator

Now let’s try to connect the battery and a resistor.

Turn the dial here, see what it says.

Battery

Turn the dial here; see what it says.

Battery

Let’s see how much current is flowing through the system. We need to make the current flow through the multimeter.

You might need to change the range.

Battery

Do this for each of your resistors. Let’s make a graph of the results.

Here is the symbolic way to draw this circuit.

A

Series Circuits

We can thing in “Series” if they are in a row.

What do you think happens if we put two resistors in series?

Does this formula help?

Let’s measure.

Does the order matter?

R = x L

WxH

You might need to change the range.

Battery

Let’s measure the current when we have two resistors in series

Let’s measure the current when we have two resistors in series

You might need to change the range.

Battery

Parallel Circuits

We can thing in “parallel” if they connect between the same two nodes in a circuit.

What do you think happens if we put two resistors in parallel?

Does this formula help?

Let’s measure.

Does the order matter?

R = x L

WxH

Let’s turn on a light

Pick one of your LEDs (light emitting diodes).

Place it in series with the smallest resistor.

What do you see?

Put some lights in series.

What do you see?

Put some lights in parallel.

What do you see?

Practical Question

If you have lots of lights in series and one breaks, what happens?

If you have lots of lights in parallel and one breaks, what happens?

What is a sensor?Thermometers

Pressure sensors

Acceleration sensors

Light sensors

Your multimeter

You!

We have some sensors… let’s see what they can do

Photoresistor

Put your photoresistor in series with your smallest resistor.

What happens?

Add your LED in series. What happens?

Have you seen something like this in your home?

Let’s measure the current in this circuit.

Photocell

Let’s try to measure this one.

It’s pretty delicate, so be careful.

Let’s move around and see what we get.

Tilt Sensor

Let’s try add this into your circuit.

It all gets pretty complicated quickly.

Now imagine there are about 2 billion devices on a computer chip.

2,000,000,000

What happens if we want to communicate over a long distance?

Let’s try that!

What happens to the signal?

Analog or Digital

Analog signals are like the signals that humans perceive. They can have any value.

Digital signals are like the signals that computers use. (Remember Boolean logic?) They can only have discrete values.

Analog or Digital

Analog signals are elegant, but susceptible to noise.

Digital signals are simple, and not very susceptible to noise.

Which one would be better for long distance communication?

http://www.fcc.gov/cgb/consumerfacts/digitaltv.html