OHMs Law Magic of Electrons 2011 Project Lead

Ohm’s Law • • Georg Ohm’s Law Chart Ohm’s Law Practice This presentation is

Georg Ohm Georg Simon Ohm 1789 -1854 German Physicist / School Teacher Discovered the

Ohm’s Law If you know 2 of the 3 quantities, you can solve for

Ohm’s Law Chart Cover the quantity that is unknown. V I R Solve for

New Prefixes m. A Milliamp = 0. 001 amps KΩ Kilo ohm = 1000

When making circuit measurements, it is important to always work Equivalent The Equivalent Unitsinare…

OR Ω V A For our lab, we will be using V, KΩ and

Remember our Multimeter? Let’s look at how they are used to measure variables in

Measuring Voltage Measure across a component. Switch Battery Resistor Light

Measuring Current Circuit flow must go through the meter. Switch Battery Resistor Light

Measuring Resistance Measure across the component being tested. Power must be off or removed

Ohm’s Law Practice Create a series circuit with a DC source and the two

Ohm’s Law Practice Calculating Resistance • Use Ohm’s Law to calculate the total resistance

Ohm’s Law Practice Create a series circuit with a DC source and fixed resistors

Ohm’s Law Practice Calculating Voltage • Use Ohm’s Law to calculate the voltage of

Ohm’s Law Practice Calculating Current • Use Ohm’s Law to calculate the current of

Answer the conclusion questions on your Activity Sheet!

Image Resources Microsoft, Inc. (2009). Clip Art. Retrieved January 13, 2009, from http: //office.

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Ohm’s Law • • Georg Ohm’s Law Chart Ohm’s Law Practice This presentation is intended to be used with Activity 6. 2. 4 Ohm’s Law.

Georg Ohm Georg Simon Ohm 1789 -1854 German Physicist / School Teacher Discovered the mathematical relationship between current, voltage, and resistance

Ohm’s Law If you know 2 of the 3 quantities, you can solve for the third. Quantities Abbreviations Units Label Voltage V or E Volts V Current I Amperes A Resistance R Ohms Ω V=IR I=V/R R=V/I

Ohm’s Law Chart Cover the quantity that is unknown. V I R Solve for V V=IR

Ohm’s Law Chart Cover the quantity that is unknown. V I R Solve for I I=V/R

Ohm’s Law Chart Cover the quantity that is unknown. V I R Solve for R R=V/I

New Prefixes m. A Milliamp = 0. 001 amps KΩ Kilo ohm = 1000 ohms

When making circuit measurements, it is important to always work Equivalent The Equivalent Unitsinare… Units. KΩ V m. A

OR Ω V A For our lab, we will be using V, KΩ and m. A.

Your Turn! V V m. A KΩ I R V A Ω

Remember our Multimeter? Let’s look at how they are used to measure variables in Ohm’s Law.

Measuring Voltage Measure across a component. Switch Battery Resistor Light

Measuring Current Circuit flow must go through the meter. Switch Battery Resistor Light

Measuring Resistance Measure across the component being tested. Power must be off or removed from the circuit. Switch Battery Resistor Light

Now Back to Ohm’s Law

Ohm’s Law Practice Create a series circuit with a DC source and the two supplied fixed resistors with the color bands visible. Calculating Resistance • Power the circuit and use a multimeter to measure the voltage drop across each fixed resistor. Add those values to get the total voltage. Record that value on your activity page, using volts for your units. • Remove one of the connectors and measure the current with the power on. Record that value on your activity page, using m. A (milliamps) for your unit.

Ohm’s Law Practice Calculating Resistance • Use Ohm’s Law to calculate the total resistance delivered by the fixed resistors. Record that value on your activity page. KΩ will be your measurement unit. • Remove the fixed resistors from the circuit and determine the value of each using the color bands. Add the values together. Record that total value on your activity page. KΩ will be your measurement unit. How close were the calculated and color band resistance values?

Ohm’s Law Practice Create a series circuit with a DC source and fixed resistors V 1 and V 2. Calculating Voltage • With the power off, use the multimeter to measure the resistance of each fixed resistor. Total resistance will be the sum of each of the measured resistances. Record the resistances, and their sum, on your activity page. KΩ will be your measurement unit. • Remove one of the connectors and measure the current with the power on. Record that value on your activity page. m. A will be your measurement unit.

Ohm’s Law Practice Calculating Voltage • Use Ohm’s Law to calculate the voltage of the circuit. Record that value on your activity page. V (volts) will be your measurement unit. • Power the circuit and use a multimeter to measure the voltage drop across each fixed resistor. Add those values to get the total voltage. Record the total voltage on your activity page. m. A will be your measurement unit. How close were the calculated and measured voltage values?

Ohm’s Law Practice Create a series circuit with a DC source and fixed resistors C 1 and C 2. Calculating Current • With the power off, use the multimeter to measure the resistance of each fixed resistor. Total resistance will be the sum of each of the measured resistances. Record the resistances, and their sum, on your activity page. KΩ will be your measurement unit. • Power the circuit and use a multimeter to measure the voltage drop across each fixed resistor. Add those values to get the total voltage. Record that value on your activity page. V (volts) will be your measurement unit.

Ohm’s Law Practice Calculating Current • Use Ohm’s Law to calculate the current of the circuit. Record that value on your activity page. m. A will be your measurement unit. • Remove any one connection and measure the current. Record that value on your activity page. m. A will be your measurement unit. How close were the calculated and measured current values?

Answer the conclusion questions on your Activity Sheet!

Image Resources Microsoft, Inc. (2009). Clip Art. Retrieved January 13, 2009, from http: //office. microsoft. com/en-us/clipart/default. aspx