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B ASIC E LECTRICITY Nicola Tesla: Mad Electricity.

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Presentation on theme: "B ASIC E LECTRICITY Nicola Tesla: Mad Electricity."— Presentation transcript:

1 B ASIC E LECTRICITY Nicola Tesla: Mad Electricity

2 L ESSON 1 : C IRCUIT S YMBOLS 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.

3 L ESSON 1 : C IRCUIT S YMBOLS Examine examples of circuit components and produce a poster matching pictures of components to their symbols and energy conversions.

4 E LECTRICAL E NERGY C ONVERTERS Loudspeaker Microphone Hair straighter TV Lift going up Heater Lamp electrical sound sound electrical electrical heat electrical sound + light electrical kinetic + potential electrical heat electrical light + heat What are the energy conversions associated with each of these devices? Now watch this short video: Electricity and circuits

5 L ESSON 2/3: P RACTICAL C IRCUITS - Q UIZ B OARD

6 L ESSON 2/3: P RACTICAL C IRCUITS - T RAFFIC L IGHTS

7 L ESSON 2/3 – P RACTICAL CIRCUITS - E LECTROPLATING

8 L ESSON 4,5 E LECTRICAL 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 amperes State that an voltmeter is used to measure voltage in Volts Draw 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.

9 L ESSON 4 : E LECTRICAL MEASUREMENTS – S ERIES CIRCUIT – X MAS T REE L IGHTS 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 wire 3 x Bulb holders with 2.5v lamps 6V battery 1 x retort stands and clamps Wire strippers

10 M EASURING 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? The current is the same at all points at all points in the circuit video clip: How to use a multimeter What is current? Programs / Virtual Int1 Physics / Practical Electricity / Current

11 M EASURING C URRENT 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 circuit ?A 2A

12 M EASURING 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!)

13 M EASURING V OLTAGE 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 current A 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. ?V 6V 3V

14 L ESSON 5 : E LECTRICAL 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 wire 3 x Bulb holders with 6v lamps 6V battery 3 x retort stands and clamps Wire strippers What are the main advantages of wiring street lamps in parallel?

15 M EASURING 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!)

16 M EASURING V OLTAGE The size of the voltage across the battery in a parallel circuit is equal to the voltages across the other components. ?V 6V

17 M EASURING 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!)

18 M EASURING CURRENT IN A PARALLEL CIRCUIT In a parallel circuit: the size of the current from the battery equals the sum of the currents through each of the other components. ?A video clip: Lighting Circuit 4A2A 4A

19 A DVANTAGES 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.

20 S ERIES V PARALLEL SHOW - ME EXERCISE You will see statements appear that may apply to SERIES circuits or PARALLEL circuit. Which is it? SERIES PARALLEL These have no branches or junctions If one bulb breaks, the other bulbs in other branches stay on. Can be turned on and off by a single switch anywhere in circuit If you put more bulbs in they will be dimmer as it is harder for the current to get through- the resistance is higher Switches 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 battery These have branches and junctions If one bulb breaks, all the others go out. If you put more bulbs in they will stay bright The size of current flowing in different parts of the circuit can be different.

21 A MMETER AND V OLTMETER E XERCISES Redraw each of the following diagrams and on each, Add a meter to find the voltage across component E Add a meter to find the current through component F Now complete the exercise, Measuring current and voltage in series and parallel circuits

22 C URRENT AND V OLTAGE C LIPS Current and voltage in a circuit. Current and Voltage in a series and parallel circuit Current and Voltage in a series and parallel circuit

23 LESSON 7/8: O HM S L AW - R ESISTANCE Conduct an experimental investigation of the relationship between voltage and current through a resistor. State that voltage/current = constant State 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 Ohms law. Calculate resistance using Ohms law

24 INVESTIGATION: H OW 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

25 O HMS L AW 2 Number of batteries Voltmeter reading (Volts) Ammeter Reading (Amps)

26 O HM S L AW - R ESISTANCE An experimental investigation of the relationship between voltage and current through a resistor shows that voltage/current = constant. this is called Ohms Law The constant is called the resistance. Resistance is a measure of the opposition to the flow of current in a circuit.

27 Calculate resistance using: C ALCULATING RESISTANCE FROM AMMETER AND VOLTMETER VALUES 12V 0.1A resistance = voltage current Example: The current through a resistor is 0.1 amperes when the voltage across it is 12 volts. Calculate the resistance. resistance = voltage current = = 120

28 O HMS L AW P RACTICE 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. Solution Solution 2.A voltage of 6 volts is across a resistor where the current is 0.5 amperes. What is the value of the resistor? Solution Solution 3.Calculate the resistance of a component when a voltage of 24 V causes a current of 0.1 amperes. Solution Solution 5.A torch bulb is marked "6 V, 0.25 A". Calculate the resistance of the bulb. Solution Solution Practical Problems involving resistance

29 Beath High School - Int 1 Physics 29 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. resistance = voltage current = 4.8 =

30 2.A voltage of 6 volts is across a resistor where the current is 0.5 amperes. What is the value of the resistor? resistance = voltage current = 12 =

31 3.Calculate the resistance of a component when a voltage of 24 V causes a current of 0.1 amperes. resistance = voltage current = 240 =

32 4.A torch bulb is marked "6 V, 0.25 A". Calculate the resistance of the bulb. resistance = voltage current = 24 =

33 LESSON 9: P RACTICAL PROBLEMS INVOLVING R ESISTORS 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.

34 P RACTICAL 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 () Symbol for resistor: Symbol for variable resistor:

35 P RACTICAL USES OF RESISTORS 2 Dimmer Switch Fan Speed Scaletrix controller Petrol Gauge Heating Element Radio volume control Skin Resistance – Lie Detector


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