1. HOW FAST IS A NANOSECOND?

2. ONE-BILLIONTH OF A SECOND!!!

3. ELECTRICAL CALCULATIONS George Ohm, a German school teacher, wanted to know the relationship between electric current, voltage, and resistance, so he studied the resistance of materials. Remember, the resistance of materials depends on the object’s material, thickness, length, and temperature.

4. Ohm’s Law the ratio of Voltage (V) to Current (I) is a constant for each material. This ratio is the Resistance (R) of the material. When the Voltage is expressed in volts (V) and the current is expressed in amperes (A), the resistance is in ohms (Ω).

5. OHM’S LAW As the resistance goes up, the current goes down. As the resistance decreases, the current increases. p. 490

6. CALCULATING OHM’S LAW R = Vor V = I X R I What is the voltage if the current is 2A and the resistance is 12 Ω? Step 1: Write the equation for voltage: V = I × R Step 2: Replace the current and resistance with the measurements given in the problem, and solve. V = 2 A × 12 Ω V = 24 V

7. OHM’S LAW CALCULATIONS (CONT’D) The resistance of an object is 4 Ω. If the current in the object is 9 A, what voltage must be used? Step 1. Write the equation for voltage. V = I X R Step 2. Replace the voltage and the current with the measurements given in the problem, and solve. V = 9 A X 4 Ω V = 36 V

8. STUDYING OHM’S LAW https://phet.colorado.edu/en/simulation/ohms-law Observe what happens when you change the value of the battery voltage. What happens to the current and the resistance? If the current or resistance remains constant, why do you think? Change the value of the resistance of the resistor. How does this change the current through the circuit and the battery voltage? If the current or voltage remains constant, why do you think?

9. OHM’S LAW SIMULATION LAB Trial Electric Current (I) Resistance (Ω) Voltage (V) 1 5007.5 2 2407.5 3 484.5 4 7464.5 5 6752.9