1. 3/5 do now – on a new sheet
An incandescent light bulb is supplied with a constant potential difference of 120 volts. as the filament of the bulb heats up, what happens to its resistance and its current? – show your reasoning
Due:
20.1 notes
Ω work:
Castle learning
20.2 notes
Unit test – 3/14
Questions from packets

2. Lesson 1: Circuit Connections
Circuit Symbols and Circuit Diagrams
Two Types of Connections
Finish lab 15

3. Circuit Symbols
Voltage sources
Resistances
Measurement Devices
Other Elements
Draw a schematic circuit with three light bulbs, wires and one battery.

4. Example:
Three D-cells are placed in a battery pack to power a circuit containing three light bulbs
Only use circuit symbols in your reference table to draw the circuits

5. Two types of connections
These two examples illustrate the two common types of connections made in electric circuits. When two or more resistors are present in a circuit, they can be connected in series or in parallel.

6. Circuit Elements – Measuring Devices
Measures: VOLTAGE
Resistance: HIGH
Connect to circuit: OUTSIDE
Measures CURRENT
Resistance: LOW
Connect to circuit: INSIDE
voltmeter
ammeter

7. Meters in a circuit V A V A

8. Two types of circuits
series
parallel
As the light bulbs are added, what happens to the current going to the battery
As the light bulbs are added, what happens to the total resistance of the circuit?
If one light bulb is taken out, what happens to the other light bulbs?
As the light bulbs are added, what happens to the current going to the battery
As the light bulbs are added, what happens to the total resistance of the circuit?
If one light bulb is taken out, what happens to the other light bulbs?

9. For series circuits
As more resistors are added the overall current within the circuit decreases.
This decrease in current is consistent with the conclusion that the overall resistance increases.
If one of three bulbs in a series circuit is unscrewed from its socket, then the other bulbs immediately go out.

10. For parallel circuits
As the number of resistors increases, the overall current also increases.
This increase in current is consistent with a decrease in overall resistance. Adding more resistors in a separate branch has the unexpected result of decreasing the overall resistance!
If an individual bulb in a parallel branch is unscrewed from its socket, other bulbs are not effected.

11. Check Your Understanding
1. Observe the electrical wiring below. Indicate whether the connections are series or parallel connections. Explain each choice.
                                                                                                             

12. 2. Two electric circuits are diagrammed below
2. Two electric circuits are diagrammed below. For each circuit, indicate which two devices are connected in series and which two devices are connected in parallel.
In series? ______________
In parallel? ______________
In series ________________