# Circuits Lesson 01: Charge Lesson 02: Circuit Diagrams

Circuits Lesson 01: Charge Lesson 02: Circuit Diagrams Lesson 03: Series Circuits Lesson 04: Parallel Circuits Which Circuit? Lesson 05: Resistance Lesson 06: Voltage, Current and Resistance Lesson 07: Voltage, Current and Resistance Lesson 08: Revision Stopwatch Graph Home

Glossary

ammeter A device used to measure current. ampere The unit used to measure current. Its symbol is A. battery The scientific word for two or more cells that are joined together. cell A chemical source of voltage. The chemicals inside this device react and electrons are pushed out into the circuit. circuit A complete path that current can travel along. current The rate of flow of electric charge in a circuit. It is measured in amperes (A). electron flow The movement of negatively-charged electrons from a negative terminal around a circuit. parallel circuit A complete circuit that branches into two or more paths. potential difference The scientific name for voltage, measured in volts (V). Measured across a component, it is the difference in electrical potential energy between the two sides of the component. series circuit A complete circuit in which components are wired one after the other in a continuous loop. volt The unit used to measure potential difference (voltage). Its symbol is V. voltmeter A device used to measure potential difference (voltage). voltage Another name for potential difference. For a cell, it is the amount of energy that the cell gives to each electron pushed out into the circuit. diode A component that allows current to flow in one direction only. light dependent resistor A component whose resistance changes in response to light intensity.

ohm The unit of electrical resistance, named after Georg Ohm. Ohms law Formula used to relate current, voltage and resistance, if the temperature remains constant. R = V/I. resistance The opposition to the flow of charge. resistor A component that opposes the flow of charge. thermistor A component whose resistance changes in response to temperature. variable resistor A component whose resistance can be adjusted to vary the amount of current. Stopwatch Graph Home Double Award Syllabus:

explain why a series or parallel circuit is more appropriate for particular applications, including domestic lighting (P2.10) understand that the current in a series circuit depends on the applied voltage and the number and nature of other components (P2.11) describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how this can be investigated experimentally (P2.12) describe the qualitative effect of changing resistance on the current in a circuit (P2.13) describe the qualitative variation of resistance of LDRs with illumination and of thermistors with temperature (P2.14) recall and use the relationship between voltage, current and

resistance: voltage = current resistance V = I R (P2.15) understand that current is the rate of flow of charge (P2.16) recall and use the relationship between charge, current and time: charge = current time Q = I t (P2.17) recall that electric current in solid metallic conductors is a flow of negatively charged electrons (P2.18). Stopwatch Graph Home Separate Science Syllabus Energy and Potential Difference in Circuits explain why a series or parallel circuit is more appropriate for particular applications, including domestic lighting understand that the current in a series circuit depends on the applied voltage and the number and nature of other components describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how this can be investigated experimentally

describe the qualitative effect of changing resistance on the current in a circuit describe the qualitative variation of resistance of LDRs with illumination and of thermistors with temperature recall and use the relationship between voltage, current and resistance: voltage = current resistance V=IR understand that current is the rate of flow of charge recall and use the relationship between charge, current and time : charge = current time Q=It recall that electric current in solid metallic conductors is a flow of negatively charged electrons recall that:

voltage is the energy transferred per unit charge passed the volt is a joule per coulomb Electric charge identify materials which are electrical conductors or insulators, including metals and plastics recall that insulating materials can be charged by friction explain that positive and negative electrostatic charges are produced on materials by the loss and gain of electrons recall that there are forces of attraction between unlike charges and forces of repulsion between like charges explain electrostatic phenomena in terms of the movement of electrons recall the potential dangers of electrostatic charges, e.g. when fuelling aircraft and tankers recall some uses of electrostatic charges, e.g. in photocopiers and inkjet printers

Stopwatch Graph Home Charge 08/02/20 Aim: To generate a charge To calculate charge Starter: Where is the static electricity in the picture? Stopwatch Graph Home What did Benjamin Franklin do? Stopwatch Graph Home How is Static Charge Generated?

How can you generate static charge? Around the outside of an atom are electrons, which have a negative charge. The nucleus at the centre of an atom contains protons, which have a positive charge. Stopwatch Graph Home Charging materials Video Stopwatch Graph Home Separate Science Investigating pairs of charges Stopwatch Graph Home

Charge Separate Science Insulators can be charged by friction If a material is turned positive then electrons have been lost if the material becomes negative the electrons have been gained Like charges repel Different charges attract Stopwatch Graph Home

Demos Water Paper Stopwatch Graph Home Experimenting with static charge Stopwatch Graph Home Charge The number of electrons (or other ions)

Symbol: Q Units: coulomb (C) Charge on 1 electron = 1.6 10-19 C Charge = current x time (in C) (in A) Q uI t Q I (in s) CharlesAugustin de Coulomb (17361806) t Stopwatch Graph Home

Example questions Charge (C) Current (A) Time (s) 5 2 0.4 1 20 0.5 50

250 3 60 1) A circuit is switched on for 30s with a current of 3A. How much charge flowed? 2) During electrolysis 6A was passed through some copper chloride and a charge of 1200C flowed. How long was the experiment on for? 3) A bed lamp is switched on for 10 minutes. It works on a current of 0.5A. How much charge flowed? Stopwatch Graph Home Separate Science How are planes refuelled safely? A build up of static charge when refuelling a plane could cause an explosion.

This can be prevented by joining the delivery tanker and the fuel tank electrically with a metal wire. The wire provides a path for electricity to flow along, and so prevents the build up of any potentially dangerous static charge. Petrol Pump metal wire Stopwatch Graph Home Dangers Separate Science

Sparks are caused by electrons moving When a plane is refuelling you can get a build up of electrostatic charges Stopwatch Graph Home Separate Science How does a photocopier work? Stopwatch Graph Home Separate Science What happens in a photocopier? Stopwatch Graph Home Inkjet printer Positive

plate Separate Science A4 paper Fine nozzle Negative plate The ink droplets are charged as they thrust against the nozzle The droplets are deflected as they pass between two electrically charged plates The amount of charge, i.e. the size and direction of the voltage, on the plates keeps changing to drive each droplet to the right place on your paper What charge will the droplets deflected upwardly have? Why? They will be negatively charged, because -ve charges are attracted by the positive plate at the top and repelled by the negative plate

at the bottom. Stopwatch Graph Home Separate Science How does spray painting cars work? Stopwatch Graph Home Separate Science How does static charge reduce pollution? A precipitator in the chimney of a power station uses static electricity to filter smoke particles from waste gases. The smoke particles pass through a charged grid and pick up a negative charge. They are then attracted

to the positively-charged collecting plates. The smoke particles lose their charge and fall back down the chimney, so the waste gases emitted are free of polluting smoke. positivelycharged metal plates smoke particles metal grid at a high voltage Stopwatch Graph Home Uses

Separate Science Electrostatic charges are used in photocopiers, inkjet printers, spray paints and precipitators Stopwatch Graph Home Separate Science Static electricity useful or a problem? Stopwatch Graph Home Van de Graaff generator Brainiac Stopwatch Graph Home

Anagrams Stopwatch Graph Home Multiple-choice quiz Stopwatch Graph Home Charge recap Aim To generate a charge To calculate charge Stopwatch Graph Home Circuit Diagrams 08/02/20

Aim Use circuit symbols Understand circuit diagrams Starter: True or False (back of books) 1) Voltage can also be called potential difference. 2) There must be a gap in a circuit for a current to flow. 3) Electrons carry energy round a circuit. 4) A light bulb transfers electrical energy into heat and light. 5) Current is measured in volts. 6) If more electrons start flowing round a circuit the current gets smaller Stopwatch Graph Home - - -

- - - - - - - - Stopwatch Graph Home Circuit symbols

Stopwatch Graph Home Circuit Symbols Wire Motor Connected Wire Fuse Non connecting wire Buzzer Cell Diode Battery

Bulb Power supply Switch Resistor Thermistor Variable Voltmeter Ammeter Resistor Light Stopwatch Graph Dependant Home Could you draw the circuit?

Stopwatch Graph Home Why Use Circuit Diagrams? Stopwatch Graph Home Types of Circuits Stopwatch Graph Home - - - - - If there is only one path for the current we say the bulbs are - connected in SERIES.

- - - Stopwatch Graph Home - - - - - the current has two - Here routes. -Any circuit with more than one - route means that the bulbs are connected in PARALLEL. Stopwatch Graph Home

- - - - - If a wire is connected around the bulb all the current will bypass the bulb and it goes out - - - -

- - - - - - - We call this a SHORT CIRCUIT Stopwatch Graph Home Which circuit diagram? Stopwatch Graph Home

Building Circuits Practise 1 1 1 1 Power Pack set at 3V

2 Bulbs Switch 1 Motor Buzzer 6 Wires Voltmeter 2 Croc Clips Draw each circuit first When Connecting Parallel circuits connect up the series section first. make sure you have that right. then add at the parallel branch. Make sure they connect where the blobs are in the circuit. Measure the Voltage across each component and the power pack and note it down on your circuit diagram The buzzers need to be connected the correct way Stopwatch Graph Home 2 1

3 M M 4 5 6 M Stopwatch Graph Home Stopwatch Graph Home Circuit Diagrams recap

Aim Use circuit symbols Understand circuit diagrams Homework Stopwatch Graph Home Series Circuits 08/02/20 Aims: To define Current, Voltage and Resistance To investigate current and voltage in series circuits Quiz: Battery Diode

Power supply Power supply Resistor Switch Voltmeter Voltmeter Ammeter Thermistor Variable Resistor Light Dependant Light Resistor (LDR) Stopwatch Graph Home

Dependant Potential Difference The push on electrons in a circuit. so bigger push, faster electrons, more current, brighter bulb Symbol: V Units: volts (V) A.k.a. Voltage Alessandro Giuseppe

Antonio Anastasio Volta (1745-1827) Stopwatch Graph Home Current The number of electrons flowing past a point in a circuit. So faster electrons or more electrons, bigger current, brighter bulb Conventional Current flows

from positive to negative however electrons are negative so they really flow from negative to positive Symbol: I Units: ampere (A) (ampere = amps) Andr-Marie Ampre (1775-1836) Stopwatch Graph Home Representing current direction Stopwatch Graph Home Resistance

How hard it is for a current to flow through a material. So bigger resistance but same voltage gives a smaller current Symbol: R Units: ohms () George Simon Ohm (1789-1854) Stopwatch Graph Home Analogy 1: Cross Country Run

Copy down the sketch on the board and annotate it. USE MOST OF A PAGE LEAVE SPACE FOR FURTHER ADDITIONS NEXT LESSON PE Teachers = Voltage Pupils = electrons Rate of pupils moving = Current

Other Teachers counting Pupils = Ammeter Obstacles = Resistances (e.g. Resistors, bulbs, motors ...) Short cuts = Short circuits Stopwatch Graph Home Experiment Follow the experiment sheet DO NOT WRITE ON THE SHEET Stopwatch Graph Home

Series circuits experiment NOTE: Voltage Reading on 3 bulbs, 1 battery is wrong should be 0.67 V Stopwatch Graph Home Current in a Series Circuit Copy the circuit into your books Measure the current at points A1, A2 and A3 Write down your readings: What has happened to the current? A3 A1 A1 =

A2 = A3 = A1 = A 2 = A 3 A2 Electrons are never ever used up So, the current is the same in all parts of a series circuit. Stopwatch Graph Home Voltage in a Series Circuit Copy the circuit into your books Measure the voltage at points V1, V2 and V3 Write down your readings:

V1 V1 = V2 = V3 = V1 = V 2 + V 3 V2 V3 In a series circuit, the voltage supplied by the battery is shared by the components. So, the sum of the voltage across the components equals the battery voltage. Stopwatch Graph Home Series Circuits recap

Aims: To define Current, Voltage and Resistance To investigate current and voltage in series circuits Stopwatch Graph Home Parallel Circuits 08/02/20 Aims: To experimentally establish the behaviour of current and voltage in parallel circuits Starter: (back of books) Which is the odd one out? A B

C D Stopwatch Graph Home Potential Difference Across Cells Batteries are made of multiple cells For instance a car battery has at least 6 To work out the voltage of the battery just add together the voltage of the cells. Q: What is the total potential difference of 2 x 1.5V batteries in series? A: V = 1.5 + 1.5 =3V Stopwatch Graph Home Work out the Potential Difference of the Following (dont forget positive and negative

ends) b) a) 1.5+1.5+1.5 = 4.5V c) 1.5-1.5 = 0V d) 1.5+1.5-1.5 = 1.5V 1.5+1.5-1.5-1.5 = 0V Stopwatch Graph Home Experiment

Follow the experiment sheet DO NOT WRITE ON THE SHEET Stopwatch Graph Home Parallel Circuits Experiment Stopwatch Graph Home Current in a Parallel Circuit Copy the circuit into your books Measure the current at points A1, A2 and A3 Write down your readings: What has happened to the current?

A1 A6 A3 A2 A5 A4 A1 A2 A3 A4 A5 A6 = = = =

= = A1 = A2 + A3 A4 + A5 = A6 The electrons must choose which way to go So, the current is not the same in all parts of a parallel circuit. Stopwatch Graph Home Potential difference in parallel circuits V1 V2

Copy the circuit into your books Measure the voltage at points V1, V2 and V3 Write down your readings: V1 = V2 = V3 = V1 = V 2 = V 3 V3 In a parallel circuit, the potential difference across each bulb is the same as the potential difference across the battery. Stopwatch Graph Home Summary Movie

Current Voltage Series Stays the same Split up across components Parallel Split up between branches Stays the same Stopwatch Graph Home

Comparing circuits Stopwatch Graph Home Uses of Circuits There are two main reasons why parallel circuits are used more commonly than series circuits: 1) Extra appliances (like bulbs) can be added without affecting the output of the others (they are all as bright as each other) 2) If one appliance breaks it wont affect the others either Stopwatch Graph Home An example question: 6V A3 3A A1 V1

A2 V2 V3 An example question: 6V 3A 3A 2A 6V 1A 3V 3V Resistance

08/02/20 Aims: To understand the affect of increasing resistance To use Ohms law To interpret a current voltage graph Starter: Stopwatch Graph Home Which Resister is Which? 1. Setup the circuit 2. Use the power pack to change the voltage 3. Make sure you get at least 5 different results. 4. Write your results in a table 5. Repeat for the other two resisters

6. Plot your results on a graph 7. V on the X axis 8. I on the Y axis 9. Calculate the gradient of your graph (1/gradient = A V Stopwatch Graph Home Stopwatch Graph Home I V Stopwatch Graph Home

Ohms Law Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me. The resistance of a component can be calculated using Ohms Law: George Simon Ohm 1789-1854 Voltage = Current x Resistance (in V) (in A) V (in ) Very = Important x Rabbits

I R Stopwatch Graph Home An example question: Ammeter reads 2A A V 1) What is the resistance across this bulb? 2) Assuming all the bulbs are the same Voltmeter reads 10V what is the total resistance in this circuit?

Stopwatch Graph Home Resistance recap Aims: To understand the affect of increasing resistance To use Ohms law To interpret a current voltage graph Stopwatch Graph Home Voltage, Current and Resistance 1 08/02/20 Aims: To use Ohms law To interpret a current voltage graphs of diodes, bulbs and resistors Starter:

Copy and Complete the Table Symbol Units Unit Symbol Charge Q coulomb C Current I Amps

Resistance R Voltage Power Energy Stopwatch Graph Home Ohmic Resistor: I V Stopwatch Graph Home Ohms Law Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me.

The resistance of a component can be calculated using Ohms Law: George Simon Ohm 1789-1854 Voltage = Current x Resistance (in V) (in A) V (in ) Very = Important x Rabbits I R Stopwatch Graph Home

An example question: Ammeter reads 2A A V Voltmeter reads 10V 1) What is the resistance across this bulb? 2) Assuming all the bulbs are the same what is the total resistance in this circuit? Homework Worksheet

Stopwatch Graph Home Voltage and Current in a Diode 1. Setup the circuit 2. Use the Rheostat to change the voltage 3. Make sure you get at least 10 different results both positive and negative. 4. Write your results in a table 5. Plot your results on a graph 6. V on the X axis 7. I on the Y axis 8. Repeat for a bulb A A

V V Stopwatch Graph Home Investigating current and voltage Stopwatch Graph Home Voltage, Current and Resistance 1 recap Aims: To use Ohms law To interpret a current voltage graphs of diodes, bulbs and resistors Stopwatch Graph Home Voltage, Current and Resistance 2

08/02/20 Aims: To use Ohms law To interpret a current voltage graphs of diodes, bulbs and resistors Stopwatch Graph Home Current voltage graphs Stopwatch Graph Home current (A) Is resistance the same in all wires? copper nichrome voltage (V) This means that the copper wire has a lower resistance than

the nichrome wire. What does the gradient tell you about resistance? The steeper the gradient of a current-voltage graph, the lower the resistance of the wire. Stopwatch Graph Home Current voltage graphs Stopwatch Graph Home Current-voltage graph for a bulb Stopwatch Graph Home Current voltage graph for a diode Stopwatch Graph Home Current-Voltage Graphs I

I V 1. Resistor 2. Bulb I V V 3. Diode Draw and explain the shape of each graph. Stopwatch Graph Home Thermistor Use a multimeter, a thermistor and your fingers to

answer the question below and then copy it into you book A thermistor lets through more current when it is hot because its resistance decreases _______ Resistance / x x x x x x

Answer in full sentences 1. What can you use a thermistor to sense? 2. Name 2 places you will find one in your home x x x Temperature / C Stopwatch Graph Home Light Dependant Resistors (LDR) Use a multimeter, a LDR and your fingers to answer the question below and then copy it into you book x x x

x x x Answer in full sentences 1. What can you use a LDR to sense? 2. Where would you find one outside? Resistance / k When light falls on an more LDR it lets through _______ current because its resistance falls. x x x

Light intensity Stopwatch Graph Home Voltage, Current and Resistance 2 recap Aims: To use Ohms law To interpret a current voltage graphs of diodes, bulbs and resistors Stopwatch Graph Home Revision 08/02/20 Aims: Revise Stopwatch Graph Home

Safety device How it works / Notes Melts when too much current flows. Fuse Value of fuse must be higher than current drawn by the device Must be in live wire Breaks the circuit when too much current flows Circuit Breaker Must be in live wire Can be reset Protects from shock with metal cased Earth

Double Insulated Plastic Insulator appliances Any charge on outside case will be dissipated to earth (also causing the fuse to melt) Plastic exterior means that even if live wire touches case user will not receive a shock Grips outer cable and prevents strain on the inner coloured wires. Is an insulator, stops current flowing from wire Stopwatch Graph Home Earth Wire Live Wire

Fuse Neutral Wire Outer Insulatio n Cable Grip Stopwatch Graph Home Definitions Definition Symb ol Unit Unit Symbol

Voltage Push on the electrons V Volts V Current Rate of flow of electrons I ampere A

Charge Total number of charged particles Q coulom b C Energy Amount of energy given to a component E joule

J Resistanc How hard it is for electrons to e flow R ohm Power P watt W How fast energy is transferred

Stopwatch Graph Home Equations Mnemonic Equation Units Exercise Is Very tiring E=IVt J=AVs Peter Is a Veggie P=IV W=AV

QuIt Q=It C=As Very Important Rabbits V=IR V=A Stopwatch Graph Home IV Graphs 1/gradient = Resistance So steeper the graph lower the resistance I

I V 1. Resistor 2. Bulb I V V 3. Diode Stopwatch Graph Home Circuits Series Circuits: Less Cabling

Series Circuit Parallel Circuit Parallel Circuits: Current same Same voltage across all Voltage split components If one breaks rest still work Copy down the sketch on the board and annotate it. split same PE Teachers = Voltage Pupils = electrons

Rate of pupils moving = Current Other Teachers counting Pupils = Ammeter Obstacles = Resistances (e.g. Resistors, bulbs, motors ...) Short cuts = Short circuits Stopwatch Graph Home Definition Symbol Voltage Push on the electrons V Current Rate of flow of electrons

Charge Total number of charged particles Energy Amount of energy given to a component Resistance How hard it is for electrons to flow Power How fast energy is transferred Unit Volts Unit Symbol

V Safety Features: Double Insulation: Outer case is _____ so it will always be safe to touch. Insulation: _____ outside cable safe to touch Earthing: outside casing connected to _____ Circuit Breaker: Trips if too big a ____ flows Fuse: _____ if too big a ____ flows Wiring a Plug: Fuse on the live Wire Green/Yellow: Earth Brown: ______ Blue: _______ Definitions Equation s Hazards: Frayed Cables

Damaged Plugs Water Dont play with sockets Mains Electricity Mnemonic Equation Units Exercise Is Very tiring E=IVt J=AVs

Series and Parallel Circuits Peter is a Veggie QuIt Very Important Rabbits Series Circuit Parallel Circuit Current Voltage Circuits IV Graphs

Advantage Series: Advantage Parallel: Resistor Bulb I Diode I V I V V Component

Function Symbol Diode Only lets the current through one way Thermistor Senses _____ (low ______ high _____) LDR Senses _____ (low ______ high _____) Stopwatch Graph Home Definition Symbol

Unit Unit Symbol Voltage Push on the electrons V Volts V Current Rate of flow of electrons I

ampere A Charge Total number of charged particles Q coulomb C Energy Amount of energy given to a component E

joule J Resistance How hard it is for electrons to flow R ohm Power How fast energy is transferred P watt

W Safety Features: Double Insulation: Outer case is plastic so it will always be safe to touch. Insulation: plastic outside cable safe to touch Earthing: outside casing connected to earth Circuit Breaker: Trips if too big a current flows Fuse: melts if too big a current flows Wiring a Plug: Fuse on the live Wire Green/Yellow: Earth Brown: live Blue: neutral Definitions Equation s

Hazards: Frayed Cables Damaged Plugs Water Dont play with sockets Mains Electricity Mnemonic Equation Units Exercise Is Very tiring E=IVt

J=AVs Peter is a Veggie P=IV W=AV QuIt Q=It C=As Very Important Rabbits V=IR V=A Series and

Parallel Circuits Circuits IV Graphs Series Circuit Parallel Circuit Current same split Voltage

split same Less Cabling If one breaks rest still work and/or same voltage Resistor Bulb I Diode I V I V

V Component Function Symbol Diode Only lets the current through one way Thermistor Senses Temp (low resistance high temp) LDR Senses Light (low resistance high light)

Stopwatch Graph Home Stopwatch Graph Home Stopwatch Graph Home Stopwatch Graph Home Stopwatch Graph Home Circuit Symbols Wire Motor Connected Wire Fuse Non connecting wire

Buzzer Cell Diode Battery Bulb Power supply Switch Resistor Thermistor Variable Voltmeter Ammeter Resistor

Light Stopwatch Graph Dependant Home Stopwatch Graph Home

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