1. Electricity
Electric Current

2. Electric Current
The flow of charges through a wire or conductor is called an electric current

3. Electric Current Current is the flow of electrons (e-)
Current (I) is measured in amperes (A)

4. Electric Current Charges flow from high voltage to low voltage
A voltage difference is the push that causes charges to move
Voltage difference is measured in volts (V)

5. Electric Current
For charges to flow, the wire must always be connected in a closed path, or circuit

6. Sources of Electricity
Dry cell battery - produces a voltage difference between its zinc container and carbon rod, causing current to flow between them
Wet cell battery - contains two connected plates made of different metals in a conducting solution
Wall sockets - a voltage difference across the two holes of an electrical outlet provided by a generator at a power plant

7. Resistance
The tendency for a material to oppose the flow of electrons, changing electrical energy into thermal energy and light
All materials have some electrical resistance

8. Resistance Resistance (R) is measured in ohms (Ω)
Making wires thinner, longer, or hotter increases their resistance

9. The current in a circuit equals the voltage difference divided by the resistance

10. Applying Ohm’s Law

11. 1.3

12. 1.3
1.3W
3.9V
3.9

13. Practice Problem

14. Practice Problem V I R
I = V / R
I = 1.5V / 2W
I = 0.75A