1. Electric Circuits

2. Objectives Distinguish between series and parallel connections
Calculate the current, voltage, and equivalent resistance for devices connected in series and parallel
Construct a voltage divider
Describe the features of a multi-meter and explain how to use it in a circuit

3. Electric Circuit Components
Capacitor
Stores charge
Creates a potential difference
Source of energy
Resistor
“Opposes” current (charge flow)
“Uses” potential difference
Dissipates energy

4. Electric Circuits Electric current requires two conditions
A “closed” circuit, or complete path for charges to flow
A potential difference, or voltage source (usually a cell or battery)

5. Electric Circuits Two types of electric circuits
Series (only one current path)
Parallel (more than one current path, i.e. “branches”)

6. Equivalent Resistance
Series resistors
Resistors in series add together

7. Current
The current through a circuit component is equal to the voltage divided by the resistance
Textbook, Pg. 533

8. Voltage
The voltage “drop” or potential difference across a circuit component equals the product of the current and the resistance
Textbook, Pg. 534

9. Voltage Divider
Series circuit used to produce a voltage source of desired magnitude from a higher-voltage battery
Textbook, Pg. 535

10. Practice Problems Textbook, Page 534 #1 – 5
Textbook, Page 536 – 537 (Examples)
Textbook, Page 537 #6 – 9

11. Equivalent Resistance
Parallel resistors
Resistors in parallel add together as the reciprocals
Hint: Remember to invert the sum to find Req
Textbook, Pg. 539

12. Kirchoff’s Laws Voltage Current Conservation of energy
Conservation of charge

13. Conservation of Energy
The sum of potential “drops” or voltages in a circuit equals the source
In a series circuit, all the voltages add up to equal the source
In a parallel circuit, the voltage applied to each branch is equal to the source

14. Conservation of Charge
The sum of all currents in a circuit is equal to the current leaving the source
In a series circuit, the current is the same at every point
In a parallel circuit, the sum of all currents entering any junction is the same as the sum of all currents leaving the junction

15. Series-Parallel Circuit
What is the voltage drop across each resistor and the current flowing through them?

16. Practice Problems
Textbook, Page 540 #10 – 12
Textbook, Page 547 #13

17. Measurements Voltmeter Ammeter Ohm-meter Multimeter
Measures potential difference (volts)
DVM (digital voltmeter)
Ammeter
Measures current (amps)
Galvanometer (very sensitive ammeter)
Ohm-meter
Measures resistance (ohms)
Multimeter
Measures all three

18. Measurements Voltmeter Ammeter Ohm-meter Parallel Series
Disconnect power
Isolate resistor from circuit
Textbook, Pg. 547