1. Voltage, Current, and Resistance
Ohm’s Law

2. https://youtu.be/TaPgSWdcYtY
Lightning Strikes

3. Voltage produces a flow of charge, or current, within a conductor
Voltage produces a flow of charge, or current, within a conductor. The flow is restrained by the resistance it encounters.
When the ends of an electric conductor are at different electric potential energies, charge flows from one end to the other.

4. When temperature is at equilibrium, the flow of heat ceases.
34.1 Flow of Charge
Heat flows through a conductor when a temperature difference exists. Heat flows from higher temperature to lower temperature.
When temperature is at equilibrium, the flow of heat ceases.

5. When temperature is at equilibrium, the flow of heat ceases.
34.1 Flow of Charge
Heat flows through a conductor when a temperature difference exists. Heat flows from higher temperature to lower temperature.
When temperature is at equilibrium, the flow of heat ceases.
Charge flows when there is a potential energy difference (voltage) between the ends of a conductor.

6. 34.1 Flow of Charge
Water flows from higher pressure to lower pressure. The flow will cease when the difference in pressure ceases.

7. 34.1 Flow of Charge
Water flows from higher pressure to lower pressure. The flow will cease when the difference in pressure ceases.
Water continues to flow because a difference in pressure is maintained with the pump. The same is true of electric current.

8. 34.2 Electric Current Measuring Current
Electric current is measured in amperes, symbol A.
An ampere is the flow of 1 coulomb of charge per second.
When the flow of charge past any cross section is 1 coulomb (6.24 billion billion electrons) per second, the current is 1 ampere.

9. Measuring Current and Voltage

10. Resistance
Resistance is an object’s ability to resist or obstruct electric current from passing through it.
All objects have some resistance to electric current—some more than others.
The amount of resistance a certain object can supply is measured in “Ohms” and we use the Greek letter Ω to represent this.

12. Voltage (V) Current (I) Resistance (Ω) Difference in potential energy
Measured in VOLTS V
Current (I)
How quickly charge flows
Measured in AMPS A
Resistance (Ω)
How much the current is obstructed
Measured in OHMS Ω

13. Ohm’s Law
Current is directly proportional to voltage.

14. Ohm’s Law Current is directly proportional to voltage.
Current is inversely proportional to resistance.

15. Ohm’s Law Voltage causes current; resistance decreases current.

16. Ohm’s Law Voltage causes current; resistance decreases current.
Put it together, and Ohm’s Law states:

17. Ohm’s Law Voltage causes current; resistance decreases current.
Put it together, and Ohm’s Law states:

19. Ohm’s Law Example 1
A toaster with a resistance of 18 Ω is connected to an outlet (V=120 V). What is the current going through the bulb?

20. Ohm’s Law Example 2
One AA-battery (1.5 Volts) is connected to a small bulb, resulting in a current of A. What is the resistance of the bulb?