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
Lesson 1: Circuit Connections
1. Circuit Symbols and Circuit Diagrams
2. Two Types of Connections
Finish lab 15
Circuit Symbols
Voltage sources
Resistances
Measurement
Devices
Other Elements
• Draw a schematic circuit with three light
bulbs, wires and one battery.
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
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.
Circuit Elements – Measuring Devices
voltmeter
ammeter
Measures: VOLTAGE
Resistance: HIGH
Connect to circuit: OUTSIDE
Measures CURRENT
Resistance: LOW
Connect to circuit: INSIDE
Meters in a circuit
V
A
V
A
Two types of circuits
• http://phet.colorado.edu/en/simulation/circuitconstruction-kit-dc
series
1. As the light bulbs are
added, what happens
to the current going
to the battery
2. As the light bulbs are
added, what happens
to the total resistance
of the circuit?
3. If one light bulb is
taken out, what
happens to the other
light bulbs?
parallel
1. As the light bulbs are
added, what happens
to the current going to
the battery
2. As the light bulbs are
added, what happens
to the total resistance
of the circuit?
3. If one light bulb is
taken out, what
happens to the other
light bulbs?
For series circuits
1. As more resistors are added the overall
current within the circuit decreases.
2. This decrease in current is consistent with the
conclusion that the overall resistance
increases.
3. If one of three bulbs in a series circuit is
unscrewed from its socket, then the other
bulbs immediately go out.
For parallel circuits
1. As the number of resistors increases, the
overall current also increases.
2. 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!
3. If an individual bulb in a parallel branch is
unscrewed from its socket, other bulbs are
not effected.
Check Your Understanding
1. Observe the electrical wiring below. Indicate whether
the connections are series or parallel connections.
Explain each choice.
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 ________________
In parallel? ______________