Download presentation

Presentation is loading. Please wait.

Published byIrene Marshall Modified over 2 years ago

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, 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

2
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

3
Resisting the Movement of Charge Topic 3 Pages 279- 291

4
Different Types of Circuits Series Circuit: ▫Only 1 current path! ▫All moving charges travel through each component in a circuit Parallel Circuit: ▫Several current paths ▫The total current is divided with charges travelling through each branch, or part of the circuit.

5
House Wiring Most circuits around the house are parallel ▫The 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!

6
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.

7
Remember: ▫Current is movement of electrons through conductors ▫Voltage is what makes electrons move ▫Resistance is what opposes the motion of the electrons. ▫A good conductor has LOW resistance ▫A poor conductor has HIGH resistance

8
The unit for resistance is ohm (Ω) ▫Measured using an ohmmeter or ▫Multimeter

9
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

10
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?

11
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)?

12
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

13
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 resistance ▫Changes with temperature, light, voltage, etc. Types: rheostats, thermistors, varistors ▫Examples: Thermostat, dimmer-switch, surge protector

14
To Do: Read page 291 about the cross-section of a wire. Resistance Calculations Worksheet Topic 3 Review ▫Pg. 291, #1-5

Similar presentations

OK

Circuits Electric Circuit: a closed path along which charged particles move Electric Current: the rate at which a charge passes a given point in a circuit.

Circuits Electric Circuit: a closed path along which charged particles move Electric Current: the rate at which a charge passes a given point in a circuit.

© 2018 SlidePlayer.com Inc.

All rights reserved.

By using this website, you agree with our use of **cookies** to functioning of the site. More info in our Privacy Policy and Google Privacy & Terms.

Ads by Google

Ppt on column chromatography applications Endocrine system anatomy and physiology ppt on cells Ppt on introduction to production management Ppt on construction of 3 phase induction motor Ppt on shell scripting definition Run ppt on raspberry pi Ppt on db2 introduction to computers Ppt on reflection and refraction Ppt on abo blood grouping system Ppt on subsoil investigation