2Lesson 1 : Circuit Symbols Draw and identify the circuit symbol for a battery, lamp, switch, resistor, motor, and variable resistor.State that lamps, heaters and motors and buzzers convert electrical energy into other forms.
3Lesson 1 : Circuit Symbols Examine examples of circuit components and produce a poster matching pictures of components to their symbols and energy conversions.
4Electrical Energy Converters What are the energy conversions associated with each of these devices?LoudspeakerMicrophoneHair straighterTVLift going upHeaterLampelectrical soundsound electricalelectrical heatelectrical sound + lightelectrical kinetic +potentialelectrical light + heatNow watch this short video: Electricity and circuits
8Lesson 4,5 Electrical measurements in circuits State that an ammeter is used to measure current in Amps.Draw and identify the circuit symbol for an ammeter.Draw a circuit diagram showing the correct position of an ammeter in the circuit.State that current is a flow of charge and is measured in amperesState that an voltmeter is used to measure voltage in VoltsDraw and identify the circuit symbol for a Voltmeter.Draw a circuit diagram showing the correct position of a voltmeter in the circuit.State that voltage is the electrical push and is measured in Volts.State that the voltage is the same for all components connected in parallel.
9Lesson 4 : Electrical measurements – Series circuit – Xmas Tree Lights Xmas tree lights are wired in series – in a line one after the other.Connect three bulbs in series as shown in the diagram.Use retort stands as model tree!You will need:Connecting wire3 x Bulb holders with 2.5v lamps6V battery1 x retort stands and clampsWire strippers
10Measuring currents in the circuit What is current?Programs / Virtual Int1 Physics / Practical Electricity / CurrentWatch as you are shown how to measure the currents in the circuit you have just built.Now go and measure the currents from the battery and through each of the lamps.Can you notice a pattern?The current is the same at all points at all points in the circuitvideo clip: How to use a multimeter
11Measuring Current 2A ?A ?A 2A 2A ?A Current is the flow of tiny electric charges around a circuit.An ammeter is used to measure the current through a circuit, measured in amperes (A)To connect an ammeter we have to break the circuit and put the ammeter in series with the other components.The size of a current in a series circuit is the same at all points in the circuit2A?A?A2A2A?A
12Measuring voltages in the circuit Watch as you are shown how to measure the voltages in the circuit you have just built.Now go and measure the voltages across the battery and each of the lamps.Can you notice a pattern?The voltages in a series circuit add to equal the battery voltage (or very similar!)
13Measuring Voltage in series Voltage can be thought of as the 'push' it exerts on charges in the circuit. A bigger voltage means a bigger 'push', resulting in a larger currentA voltmeter is used to measure voltage, in volts (V)Voltmeters are connected in parallel to either side of the component.The size of the voltage across the battery in a series circuit is equal to the sum of the voltages across the other components.6V?V3V?V3V?V
14Lesson 5 : Electrical measurements in a parallel circuit – street lights Street lights are wired in parallel and are controlled by a time switch driven by a clock. This turns the lights on and off at the correct time.Connect three bulbs in parallel as shown in the diagram.Use retort stands as model lamp posts.You will need:Connecting wire3 x Bulb holders with 6v lamps6V battery3 x retort stands and clampsWire strippersWhat are the main advantages of wiring street lamps in parallel?
15Measuring voltages in the circuit Watch as you are shown how to measure the voltages in the circuit you have just built.Now go and measure the voltages across the battery and each of the lamps.Can you notice a pattern?The voltages in a parallel circuit are all the same (or very similar!)
16Measuring VoltageThe size of the voltage across the battery in a parallel circuit is equal to the voltages across the other components.?V6V?V6V?V6V
17Measuring currents in the circuit Watch as you are shown how to measure the currents in the circuit you have just built.Now go and measure the currents from the battery and through each of the lamps.Can you notice a pattern?In a parallel circuit the current from the battery equals the sum of the currents through the lamps (or very similar!)
18Measuring CURRENT in a parallel circuit the size of the current from the battery equals the sum of the currents through each of the other components.?A4A2A?A?A2A4A?Avideo clip: Lighting Circuit
19Advantages of wiring street lamps in parallel: When bulbs are connected in parallel each bulb gets the full battery voltage.Each bulb lights with equal brightness.If one or more bulbs stop working or are removed the rest continue lighting.
20Series v parallel show-me exercise You will see statements appear that may apply to SERIES circuits or PARALLEL circuit. Which is it?PARALLELSERIESThese have no branches or junctionsIf one bulb breaks, the other bulbs in otherbranches stay on.Can be turned on and off by a single switchanywhere in circuitIf you put more bulbs in they will be dimmeras it is harder for the current to get through- the resistance is higherSwitches can be put into the circuit to turn on and off all or part of the circuit.The sum of voltages across all the components is equal to the voltage across the cell or batteryThese have branches and junctionsIf one bulb breaks, all the others go out.If you put more bulbs in they will stay brightThe size of current flowing in different parts of the circuit can be different.
21Ammeter and Voltmeter Exercises Redraw each of the following diagrams and on each,Add a meter to find the voltage across component EAdd a meter to find the current through component FNow complete the exercise, “Measuring current and voltage in series and parallel circuits”
22Current and Voltage Clips Current and voltage in a circuit.Current and Voltage in a series and parallel circuit
23lesson 7/8: Ohm’s Law - Resistance Conduct an experimental investigation of the relationship between voltage and current through a resistor.State that voltage/current = constantState that the “constant” is called the “resistance”State that resistance is a measure of the opposition to the flow of current in a circuit.State that resistance = voltage/current is called Ohm’s law.Calculate resistance using Ohm’s law
24INVESTIGATION: How does changing the voltage affect the current ? In this experiment you will use battery voltage to push current through a resistor.You will use an ammeter and a voltmeter to find how changing the voltage affects the current.Follow the instructions on the worksheet, “Voltage, Current and Resistance”
25Ohms Law 2 Number of batteries Voltmeter reading (Volts) Ammeter (Amps)1234
26Ohm’s Law - ResistanceAn experimental investigation of the relationship between voltage and current through a resistor shows thatvoltage/current = constant.this is called Ohm’s LawThe “constant” is called the “resistance”.Resistance is a measure of the opposition to the flow of current in a circuit.
27Calculating resistance from ammeter and voltmeter values Calculate resistance using:resistance =voltagecurrentExample:The current through a resistor is 0.1 amperes when thevoltage across it is 12 volts. Calculate the resistance.12V0.1Avoltagecurrent120.1=resistance == 120W
28Ohms Law Practice1. A resistor has a voltage across it of 12 volts and a current through it of 2.5 amperes.Calculate the resistance of the resistor Solution2. A voltage of 6 volts is across a resistor where the current is 0.5 amperes.What is the value of the resistor? Solution3. Calculate the resistance of a component when a voltage of 24 V causes a current of 0.1 amperes Solution5. A torch bulb is marked "6 V, 0.25 A".Calculate the resistance of the bulb SolutionPractical Problems involving resistance
29Calculate the resistance of the resistor. 1. A resistor has a voltage across it of 12 volts and a current through it of 2.5 amperes.Calculate the resistance of the resistor.voltagecurrentresistance =12=2.5=4.8 WBeath High School - Int 1 Physics
302. A voltage of 6 volts is across a resistor where the current is 0 2. A voltage of 6 volts is across a resistor where the current is 0.5 amperes.What is the value of the resistor?voltagecurrentresistance =6=0.5=12 W
313. Calculate the resistance of a component when a voltage of 24 V causes a current of 0.1 amperes. =0.1=240 W
324. A torch bulb is marked "6 V, 0.25 A". Calculate the resistance of the bulb.voltagecurrentresistance =6=0.25=24 W
33lesson 9: Practical problems involving Resistors Draw and identify the circuit symbol for a resistor and a variable resistor.State that resistors convert electrical energy into heat energy.State that an ohmmeter is used to measure resistance.State that resistance is measured in ohms.State that an increase in resistance of a circuit leads to a decrease in the current in the circuit.Give two practical uses of resistors.
34Practical uses of resistors 1 The most common use for a resistor is simply to control the size of the current flowing in part of a circuit.The larger the resistance the smaller the current.The smaller the resistance the larger the current.Resistance is measured in units of ohms (Ω)Symbol for resistor:Symbol for variable resistor: