1. Ohm’s Law Ohm’s Law Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Ohm’s Law

2. Ohm’s Law Georg Ohm Ohm’s Law Ohm’s Law Chart Ohm’s Law Practice
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Ohm’s Law
Georg Ohm
Ohm’s Law
Ohm’s Law Chart
Ohm’s Law Practice
This presentation is intended to be used with Activity Ohm’s Law.

3. Georg Ohm Georg Simon Ohm 1789-1854 German Physicist / School Teacher
Ohm’s Law
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Georg Ohm
Georg Simon Ohm
German Physicist / School Teacher
Discovered the mathematical relationship between current, voltage, and resistance

4. V=IR I=V/R R=V/I Ohm’s Law
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
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

5. Cover the quantity that is unknown.
Ohm’s Law
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Ohm’s Law Chart
Cover the quantity that is unknown. V I R
Solve for V
V=IR

6. Cover the quantity that is unknown.
Ohm’s Law
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Ohm’s Law Chart
Cover the quantity that is unknown. V I R
Solve for I
I=V/R

7. Cover the quantity that is unknown.
Ohm’s Law
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Ohm’s Law Chart
Cover the quantity that is unknown. V I R
Solve for R
R=V/I

8. New Prefixes mA
Milliamp = amps KΩ
Kilo ohm = 1000 ohms

9. When making circuit measurements, it is important to always work in Equivalent Units.
The Equivalent Units are… KΩ V mA

10. For our lab, we will be usingΩ V A
For our lab, we will be using
V, KΩ and mA.

11. Your Turn! V I R V mA KΩ V A Ω

12. Remember our Multimeter?
Ohm’s Law
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Remember our Multimeter?
Let’s look at how they are used to measure variables in Ohm’s Law.

13. Measuring Voltage Measure across a component. Switch Battery Resistor
Using a Multimeter
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Measuring Voltage
Measure across a component.
Switch
Battery
The positive and negative signs represent polarity and flow.
A digital multimeter will give a negative reading if the positive and negative terminals are reversed.
The voltage reading can be different between any measured component.
Resistor
Light

14. Measuring Current Circuit flow must go through the meter. Switch
Ohm’s Law
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Measuring Current
Circuit flow must go through the meter.
Switch
Battery
Resistor
Light

15. Measuring Resistance Measure across the component being tested.
Ohm’s Law
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Measuring Resistance
Measure across the component being tested.
Power must be off or removed from the circuit.
Switch
Battery
Resistor
Light

16. Now Back to Ohm’s Law Ohm’s Law Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Now Back to Ohm’s Law

17. Ohm’s Law Practice Calculating Resistance
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
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 mA (milliamps) for your unit.

18. Ohm’s Law Practice Calculating Resistance
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
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?

19. Ohm’s Law Practice Calculating Voltage
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Ohm’s Law Practice
Create a series circuit with a DC source and fixed resistors V1 and V2.
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. mA will be your measurement unit.

20. Ohm’s Law Practice Calculating Voltage
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
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. mA will be your measurement unit.
How close were the calculated and measured voltage values?

21. Ohm’s Law Practice Calculating Current
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Ohm’s Law Practice
Create a series circuit with a DC source and fixed resistors C1 and C2.
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.

22. Ohm’s Law Practice Calculating Current
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Ohm’s Law Practice
Calculating Current
Use Ohm’s Law to calculate the current of the circuit. Record that value on your activity page. mA will be your measurement unit.
Remove any one connection and measure the current. Record that value on your activity page. mA will be your measurement unit.
How close were the calculated and measured current values?

23. Answer the conclusion questions on your Activity Sheet!

24. Ohm’s Law
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Image Resources
Microsoft, Inc. (2009). Clip Art. Retrieved January 13, 2009, from