from yesterday… what are the 4 basic elements that a circuit includes? ▫source, conductor, load,...
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![Page 1: From yesterday… What are the 4 basic elements that a circuit includes? ▫Source, conductor, load, control Draw a simple circuit which includes 1 light bulb,](https://reader036.vdocuments.us/reader036/viewer/2022070410/56649eb75503460f94bc140e/html5/thumbnails/1.jpg)
From yesterday…•What are the 4 basic elements that a
circuit includes?Source, conductor, load, control
•Draw a simple circuit which includes 1 light bulb, a battery and a switch.
•What is potential difference?Difference in energy per unit of charge
between one point in the current and another- referred to as voltage
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Topic 2 Review:1. Matching answers:
• Load- water wheel• Switch- valve• Electric current- flow rate• Voltage- pressure• Battery- pump• Conductor (wire)- pipe
2. Drawing a circuit with a battery, a switch, a lamp, an ammeter, and conducting wires.
4. The current passing through the electric iron would be greater because an iron requires far more energy (E in joules) than the much smaller razor. Since V = E/Q (Q = E/V) the iron would require more coulombs of charge than the razor. If I = Q/t and Q is larger than I, the current would be greater
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Resisting the Movement of ChargeTopic 3Pages 279- 291
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Different Types of Circuits
•Series Circuit:Only 1 current path!All moving charges travel through each
component in a circuit
•Parallel Circuit:Several current pathsThe total current is divided with charges
travelling through each branch, or part of the circuit.
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House Wiring
•Most circuits around the house are parallelThe voltage across each load in a parallel
circuit is the same
Problem: Current through wires connected to the
source increases whenever another branch in the circuit is closed. Increases temperature and can cause fires!
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What is resistance?•Is a property of a substance that hinders
motion of electric charge and converts electric energy into other forms of energy.
• Example: light bulb with tungsten filament
vs. light bulb with copper filament.
Electrons (-) force their way through solids, overcoming resistance caused by the attraction of positively charged atomic nuclei.
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•Remember:Current is movement of electrons through
conductorsVoltage is what makes electrons moveResistance is what opposes the motion of the
electrons.
A good conductor has LOW resistanceA poor conductor has HIGH resistance
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•The unit for resistance is ohm (Ω)Measured using an ohmmeter orMultimeter
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Measuring Resistance•Resistance affects current flow and
potential difference in a circuit
Resistance= voltage (potential difference)
current
This is called Ohm’s Law:R= V I
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Let’s try some problems!
Together:What is the resistance of an electric heater,
if a current of 12.5A runs through it when it is connected to a 120V wall outlet?
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To Do:1. What is the resistance of a light bulb if a
12V battery sends a current of 2.4A through it?
2. A toaster with a resistance of 145Ω is connected to a 120V source. What current will flow through the toaster?
3. What is the potential difference across a 1500Ω resistor carrying a current of 0.075A (74mA)?
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Read page 283:•Resistors:
What are resistors?What is one problem that is encountered with
resistors?What is a major use of them?What materials are resistors commonly made of?
•Variable Resistors:What changes with variable resistors?Where are variable resistors used? Give examples
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•Resistors: control current or voltage to suit the specific needs of the loads in a circuit.
•Problems? Can be single-use, expensive, or hard to replace.
•Common use: circuit boards•Made of: metal oxides, metal film, resistance
wire
•Variable resistors don’t have a fixed resistanceChanges with temperature, light, voltage, etc.
•Types: rheostats, thermistors, varistorsExamples: Thermostat, dimmer-switch, surge
protector
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To Do:
•Read page 291 about the cross-section of a wire.
•Resistance Calculations Worksheet •Topic 3 Review
Pg. 291, #1-5