IOT POLY ENGINEERING 4-01 DRILL April 20, 2009 Ohm’s Law states that voltage equals current times resistance, V=IR. Solve the following problems. Draw

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POLY ENGINEERING4-01

DRILL April 20, 2009 Ohm’s Law states that voltage equals current times resistance, V=IR. Solve the following problems. Draw a schematic diagram and label all electrical components. Show all equations, substitutions, and box in your answers

with units.1. What is the voltage required to force 12 amperes through a 15

ohm resistor?2. How much current flows when a 9 Volt battery is connected to a

0.3 ohm resistor?3. What resistance is required to allow only 2 amperes to flow

through a 12 Volt battery?

BRING 9 Volt BATTERY TOMORROW!!!

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Solve the following problems. Draw a schematic diagram and label all electrical components. Show all equations, substitutions, and box in your answers with units.

1. What is the voltage required to force 12 amperes through a 15 ohm resistor?

15 W12 A

V=IR

V= (12 A)(15W)

V= 180 V

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2. How much current flows when a 9 Volt battery is connected to a 0.3 ohm resistor?

0.3 W9 V

V=IR

9 V= I(0.3W)

30 A= I

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3. What resistance is required to allow only 2 amperes to flow through a 12 Volt battery?

12 V

2 AV=IR

12 V= (2A)R

6 W= R


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We are going to spend the next few days exploring Electrical and Electronic Technologies.

We will be constructing electrical circuits using materials from a kit called “Mr. Circuit”.

MR.CIRCUIT KIT OBJECTIVES:1. Recognize some basic components used in electronics.2. Learn the names and schematic symbols of some electronic components.3. Learn to follow and understand electronic schematic diagrams.4. Learn the basic function of some electronic components.5. Learn how to construct electronic devices by following schematic diagrams.


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ELECTRICAL COMPONENT IDENTIFICATION

Students should be able to identify the following common electrical components by what they look like 'in-person',and by their schematic symbols.

RESISTOR fixed value potentiometerCAPACITOR ceramic electrolyticTRANSISTOR n-p-n p-n-p

DIODE standard semiconductor diode LED (light emitting diode)SWITCH push-button switch, NOSPEAKERSOLDERLESS BREADBOARD9 Volt CELL


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These are the major components of the Mr. Circuit kits.

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CAUTIONS:

When building the circuits using the Mr. Circuit kits, it is extremely important to read the instructions carefully!!!

Do not connect your 9 Volt battery to the battery snap untilyou have checked and double-checked your circuit connections. If you damage any part(s), you will be responsible for paying for their replacements.

When a paper clip is bent back and forth many times, it will break. The same is true of the metal wires on electrical components. Avoid bending the wires unless absolutely necessary.

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MORE CAUTIONS:

Some devices have a 'polarity', meaning that they have a specific positive and negative connection, and they MUST be connected properly in a circuit.

Some examples of devices with polarity:LED, electrolytic capacitor, 9V battery, diode, transistor

Please be very careful when building circuits using these types of devices.

If they are connected improperly, they may be damaged or cause a safety hazard.

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PROTOTYPE CIRCUIT BOARDS (BREADBOARDS)

In the old days, people baked their own bread and would slice the bread on a wooden breadboard.

Some electronic experimenters found the breadboard to be a suitable place for building circuits, too.

Today, we use plastic prototype boards with rows and columns, but they are still called 'breadboards'.

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Our circuit boards have lettered columns (abcde and fghij), and numbered rows (1 to 30).

Although you cannot see them completely, there are metal conductors within the breadboard.

Each numbered row from a-e is connected underneath and each numbered row f-j is connected underneath.

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For example, in row 1, we find holes A1, B1, C1, D1, and E1.

They are all 'electrically connected' beneath the breadboard.

Therefore, if you insert a wire into hole A1, and another wire into hole E1, it is the same as if the wires were touching each other.

However, hole J1 is not connected to A1 through E1.F1, G1, H1, I1, and J1 are connected to each other.


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There are two categories of resistors: 1. Fixed value resistors - these resistors have one designed value of resistance, although that value can change due to other factors, such as temperature changes.

2. Variable value resistors - these resistors are designed so that the resistance can be changed. They are sometimes called potentiometers or rheostats. An example is found in a 'dimmer' switch, or the 'volume' control on a radio.

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On our first day of electrical/electronic project work, we willstudy how a fixed value resistor works and how a potentiometer works.

Fixed value resistors utilize the ‘resistor color code’.This code assigns a number to a standard color.

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The resistor directly below with Orange-Black-Orange represents 30 times 1,000 which is equal to 30,000 ohms.

Another way to arrive at the same answer is 30 plus 3 zeros,which is equal to 30,000 ohms. The gold stripe represents a tolerance of +/- 5%.

What is the value of the resistor above?

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The resistor on the previous slide has a color code of yellow-violet-orange-gold which translates to 4-7 plus 3 zeros,or 47000 ohms +/- 5%.

Fixed value resistor schematic symbol

Potentiometer schematic symbol

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Documents

IOT POLY ENGINEERING 4-01 DRILL April 20, 2009 Ohm’s Law states that voltage equals current times resistance, V=IR. Solve the following problems. Draw