Ernest FERRERELECTRIC CIRCUITSActivities. Lesson 1
Lesson 1 Understanding electric magnitudes
Activity 1
Watch the power point presentation about the hydraulic analogy of electricity. Now check the hydraulic analogy at your school.
Voltage: look at the pressure indicator on the fire-prevention hose at different floor levels of your school. Now build a sentence, choosing the suitable words.
The water pressure (voltage) / increase / as you / go updecrease / go down
is the same whatever floor you are on
Because
upstairs / the potential energy of water / is higheris lower
downstairs / is the same
Resistance and Intensity: look at any water tap. Obviously, as it is closed no water can flow. Now open it slowly and observe that, as you open it more, water can flow.
Summarize your observations and its analogy with electric circuits by filling the blanks in the text below with suitable words from the word bank. Be careful because there are more words than blanks to fill. Some could be used more than once.
The tap is an ______for the water circuit as the electrical______is an obstruction for an electrical ______.
If the ______is closed (infinite obstruction) no ______can flow. If the electrical resistance is ______(open circuit or we put insulating materials like______, plastic, rubber, etc.) no electricity can ______.
As we ______slowly the ______the obstruction ______and the water begins to flow. As we decrease the obstruction the flow______. If we put less insulating materials (water, graphite, rust iron, steel, aluminium, ______, etc.) we see that ______the obstruction decreases the ______of the current increases.
Activity 2
Watch, read, listen to and repeat the slides and questions in the following internet presentations aboutelectric voltage or potential difference (dp) What happens if the electric voltage increases in a simple circuit?
Copy the question and correct answer or complete sentence from the quiz.
5)
6)
7)
8)
Now assemblea simple circuit with wires, switch and light bulb but use a variable power supply. What happens if we increase the voltage slowly from zero to the full voltage the bulb can tolerate?
Summarize your observations writing some sentences using the structures proposed below. The first sentence it is already done as example
Voltage / zero / ¼ / ½ / ¾ / FullThe bulb / has a very bright light / has a normal light / doesn’t light at all / has a bright light / has a dimly light
is very hot / is slightly hot / is cold / is hot / is warm
1) When the voltage is zero, the bulb doesn’t light at all and it is cold
2) When the voltage is______, the bulb______and it is ______
3)
4)
5)
Activity 3
Watch, read, listen to and repeat the slides and questions in the following internet presentationsabout electric resistance. What happens if the electric resistance increases in a simple circuit?
Copy the question and correct answer or complete sentence from the quiz
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
Now assemblea simple circuit with a battery, wires, switch and a light bulb. Now add another bulb between the last one and the power supply. Finally add a 3rd lit bulb. What canyou observe? Now remake the circuit adding a very long, long wire, adding more switches, etc.
Voltage / one bulb / two bulbs / three bulbs / Three bulbs, long wires andseveral switches
brightness picture /
Resistance / small
Summarize your observations writing some sentences using the structures proposed below. The first sentence it is already done as example.
The bulb/s / has/ havea dimly light / has/ have
a bright light / doesn’t/ don’t light at all / has/ have
a normal light
is/are warm / is/are hot / is/are very hot / is/are cold
1) When the circuit has one bulb, the bulb has a bright light and is very hot.
2) When the circuit has _____ bulbs, the bulbs have a ______light and are ______
3)
4)
The resistance is / small/medium high/very high / with / just one bulbtwo bulbs
three bulbs
The highest resistance / happens with / just one bulb
two bulbs
three bulbs / and / a long wire
a short wire
The smallest resistance
1)The resistance is______with ______.
2)The resistance is______with ______.
3)The resistance is______with ______.
The highest resistance happens with______and______
The smallest resistance happens with______and______
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Ernest FERRERELECTRIC CIRCUITSActivities. Lesson 2
Lesson 2 Electric measurements
Activity 1
You have to get into teams of two.Read the summarized transcription about how to use a multimetre while you. Then listen to the presentation on
As a 1st member of your team explain the meaning of the words written below. You can use the presentation transcription, a monolingual on-line dictionary. or an on-line encyclopaedia
Measurement is ______
Gauge is ______
Continuity is ______
Resistor code is ______
Probes are ______
Range is ______
As a 2nd member of your team, answer the following questions? Remember to begin an answer using the question..
What is a multimetre? A multimetre is…
How do you use it? I/We use it ______
How to measure continuity? We measure continuity ______
How to measure voltage?______
How to measure current?______
Activity 2
You have to get into teams of four/five. Each student in the group receives a slip of paper with part of the instructions about how to use a multimetre. There are some missing words on each slip that you have to fill in with the words from the word bank below.
- First read your slip and try to fill in the gaps.
- Now read your slip to your group and ask them to help you check/fill the gaps.
- Then the group works out the correct order of the text.
- Next listen to the proposed order of instructions other groups have and agree/disagree/correct ‘til all the class agree on the order.
- Finally each group writes a question about the text and asks/answers questions with other groups.
Activity 3
You have to get into teams of two. First write down the multimetre parts on the picture.
Now draw two probes, one red and one black and set them to the jack/s that they can be connected to.
Finally compare this multimetre with the multimetre you have in your technology workshop. Explain the similarities and the differences you have found: number of jacks,
Measurements able to do, screen pictures, etc.
Picture multimetre / Technology workshop multimetreSimilarities
Differences
Activity 4
Continuity test.No power supply is needed for continuity test, because the multimetre provides the required energy and also works as a buzzer.
The continuity test checks if electricity can pass through an electric component, this is if a connection between two points of the circuit exists.
Set the red probe to VΩ. Set the measuring wheel (knob) to Ohm, musical note. If necessary, press function button to make musical note appear on the metre screen.
Now experiment with the metre and choose/write the answer
a) Check if the continuity test works by linking the probes.
ANSWER: If the metre beeps, it’s OK/it works/it is working/it is correct.
b) Check if a spare wire is OK.
ANSWER: If the metre beeps/doesn’t beep, it’s OK/it works/it is working/it is correct.
c) Check if a wire within the circuit is OK. ANSWER:
d) Check if a switch in on position is OK.ANSWER:
d) Check if a switch in on position is OK.ANSWER:
Think what problem is happening when the multimetre beeps/doesn’t beep at the right position.
Activity 5
Resistance measurement. No power supply is needed for this test, because Ohmmetreprovides the required energy. The multimetre works as a Voltmetre and an Ammetre together, using the Ohm’s law to calculate Resistance.
The Ohmmetremeasures the opposition that substances have against the flow of electricity.
Instructions: Set the red probe to VΩ. Set the measuring wheel (knob) to Ohm. Choose the gauge according with the expected resistance value. Big resistance use M for MegaOhms (106 Ohms). Small resistances use Ohms.
Sample / Selected gauge / Measure / Insulator or Conductor?Spare wire
Bulb 12 V
Bulb 230 V
A key
Dry finger
Wet finger
Dry wood
Wet wood
Activity 6
Voltmeter measurement. To measure voltage, circuit needs power supply. The Voltmetre has a big resistance.
It measures the potential difference between two points of the circuit, which means the energy that electrons loss when they pass through an electrical component. It is used to measure the voltage effect of each electric component.
Look at the following circuits diagrams used to measure voltage.
Voltmeter serial at the battery / Voltmeter parallel at the bulb lit / Voltmeter serial at the bulb lightVoltmeter parallel at the battery / Voltmeter serial at the switch / Voltmeter parallel at the switch
Which of them do you think are wrong / correct / useless? Justify your decision.
Will the bulb light up or not, Will the main current will through the bulb circuit or the meter, Will the multimetrereadingbe high/normal/low, etc.
The first is already done:
The top left diagram (Voltmeter series at the battery) is incorrect because in this dispositionVoltmetre, as it has high resistance, prevents current from flowing through the bulb. The bulb will not light on, and the multimetre reading will be useless.
Now, it’s your turn:
The top middle diagram (Voltmeter parallel at the bulb) is______
The top right diagram (Voltmeter serial at the bulb) is______
The bottom left diagram (Voltmeter parallel at the battery) is______
The bottom middle diagram (Voltmeter series at the switch) is______
The bottom right diagram (Voltmeter parallel at the switch) is______
Now assemble the circuits respecting the voltage prescribed by your teacher and check if your predictions are true.Check for each assembly if the light bulb turns on and off. Use a Voltmetre to measure.
Instructions: Set the red probe to VΩ. Set the measuring wheel (knob) to DCV: Direct current voltage. Choose the gauge according with the expected voltage value.
Write down your measurement inside each picture above.
Complete comparative sentences about the voltage values obtained in circuits where the bulb turns on. (the same, highest that, smaller than, slightly highest than)
The voltage measured at the battery is ______the voltage measured at the bulb.
The voltage measured at the bulb is ______the voltage measured at the switch.
The voltage measured at the switch is ______the voltage measured at the battery.
Finally write a summary about multimetre use and safety.
For measuring the circuit/bulb/battery voltage...you must/mustn’t
1)
2)
3)
Activity 7
Ammetre measurement. To measure intensity, circuit needs power supply. The Ammetre has a very small,nearly zero, resistance,
It measures the flow of current through a part of the circuit, which means how many electrons pass at a given time at a point. It is used to know the current passing through a section of the circuit.
Look at the following circuits diagrams used to measure intensity.
Ammeter serial at the battery / Ammeter parallel at the bulb / Ammeter serial at the bulbAmmeter parallel at the battery / Ammeter serial at the switch / Ammeter parallel at the switch
Which of them do you think are wrong / correct / useless? Justify your decision.
Will the bulb light up or not, Will the main current will through the bulb circuit or the meter, Will the multimetre reading be high/normal/low, etc.
The first is already done:
The top left diagram (Ammetre serial at the battery) is correct because in this disposition Ammetre, as it has a very small resistance, allows current to flow through the bulb. The bulb will light on, and the multimetre reading will be normal, measuring current passing through the circuit.
Now, it’s your turn:
The top middle diagram (Ammetre parallel at the bulb) is______
The top right diagram (Ammetre serial at the bulb) is______
______
The bottom left diagram (Ammetre parallel at the battery) is______
______
The bottom middle diagram (Ammetre series at the switch) is______
______
The bottom right diagram (Ammetre parallel at the switch) is______
______
Now assemble the circuits respecting the voltage prescribed by your teacher and check if your predictions are true. Check if the lit bulb turns on and off. Use an Ammetre to measure.
Warning: Be very careful because some of the circuits are dangerous (shortcircuit) if connected over very low voltage. If possible use a power supply unit instead of a battery.
Instructions: Set the red probe to A. Set the measuring wheel (knob) to DCA: Direct current Intensity. Choose the gauge according with the expected intensity value.
Write down your measurement inside each picture above.
Why intensity measurements are always the same on circuits where the bulb turns on?ANSWER:______
Finally write a summary about multimetre use and safety.
For measuring the circuit/bulb/battery intensity...you must/mustn’t
1)
2)
3)
Activity 8
Measurement / Power on circuit? / Circuit diagram with metre, series or parallel / How the meter worksVoltmeter
Ammeter
Continuity
Ohmmeter / Circuit power on
Circuit power off
Power off & isolated element / Big resistance
Small resistance
A battery and a buzzer
A battery with a Voltmetre and a Ammetre working together
Choose the explanation that fits better with each possible measurement the multimetre (meter) can do. Series: meter inside the only possible electricity pathParallel: meter in a different electricity path.
Now summarise information with a sentence for each measurement. The first is already done...
The Voltmetre works with circuit power on. The Voltmetre has a big resistance, so it must be connected in parallel with the element we are going to measure.
The Ammetre works ______.
The Ohmmetre works ______.
The Continuity test works ______.
Activity 9
Ohm’s law: assemble a simple circuit using a variable power supply station and a meter to measure both voltage and intensity. Do measurements and take records as the voltage slowly increases from zero to the full voltage tolerated by the bulb.
Power supply voltage / Zero / ¼ ( V) / ½( V) / ¾( V) / full( V)Voltmeter at the battery(V)
Voltmeter at the bulb (V)
Ammeter (A)
Measure the resistance of the bulb alone (0 voltage) with the Ohmmeter.
Usethe Ohm’s lawVoltage (V) = Resistance (Ω) x Intensity (A)to calculate the resistance of the bulb and check if the Ohm’s law is fulfilled
Power supply voltage / Zero / ¼ ( V) / ½( V) / ¾( V) / full( V)Measured resistance / Calculated resistance using Ohm’s law. R = V/I
Bulb’s
resistance (Ω)
According with your observations, complete the sentences using increases /decreases /remains the same.
If the Voltage increases the bulb’s resistance ______.
If Intensity decreases, the bulb’s resistance ______.
Activity 10
Expand the table you did in the previous activity to fill in the information you can calculate about energy and power in your basic circuit. Remember the Power and Energy formulas you already know:
Electric Power (W) = Voltage (V) x Intensity (A)
Energy consumed or Work (kW.h) = Electric Power (W) x time working (hours)
Power supply voltage / Zero = 0 V / ¼ =___ V / ½ =___ V / ¾ =___ V / Full =___ VPower (W)
Daily (24h) consume of Energy (Kw.h)
Activity 11
Electric appliances and light bulbs always give information about the voltage required to work properly and the power they provide at the given voltage. With the compulsory advice of your parents & teachers analyse at least 12 electric appliances and lights at home or at school and record the voltage and power information. Most electrical appliances have the required information in a plate on its back or in the instructions leaflet.
Now calculate the rest of electrical magnitudes for each one, including consumption if they are connected for a whole day: 24 hours.
The first is done as an example.
- a 100 Watts bulb working at 220 Volts has a current of I(A)=P(W)/V(V)=100W/220V = 0,45A
- The bulb resistance according to Ohm’s law is R (Ω) = V(V)/ I(A) = 220 V/ 0,45A = 485 Ω
- The daily energy consumed is E(kW.h) = P (kW) x time (hours) = 100 W* 1Kw/1.000W * 24 h = 2,4 kW.h. Remember to convert W into kW by dividing by 1000!
Fill in the table with the information recorded and calculated. Suggestion: You can use a processing sheet (Excel) to calculate the results.
Electric components / Voltage use (V) / Power provided(W) / Calculated
Intensity (A) / Calculated
Resistance
(Ω) / Daily consume of Energy (Kw.h)
Incandescent bulb 100W / 220 / 100 / P/V = 0,45 / V/I = 485 / P*t/1000 = 2,4
Incandescent bulb 60 W / 220
Incandescent bulb 40 W
Energy saving bulb 12W
Blender
Washing machine
Fridge
Television “Telly”
Computer
Other appliances: DC bulb, dish washer, hair dryer, clothes dryer, toaster, HI-FI, wide screen, console, printer, speakers, radio, microwave, oven, freezer, fan, electric radiator, heater, radio, air conditioned, etc.
According with your observations complete the sentences using: increases, decreases, remains the same {Resistance...
For a given voltage, if Power increases, then{Intensity...
{Energy consume...
{Energy consume...
For a given voltage if Resistance increases, then{Intensity...
{Power...
Discuss results with your partner and justify your observations. You can use the Water circuit analogy to clarify your ideas.
Activity 12
Take an old electricity bill from home. Cut out the information about your account and bank where the bill is charged. Now analyze the information provided on the bill.
a) You pay for the right to have electricity: the power payment. (‘Potència’) This is a fixed amount for each kW you can use, even if you are not using it because you are on holiday.
The device that controls your power limit is called Main Switch or Main circuit breaker (ICP “Interruptor de Control de Potència”) If you overload your fitting, the ICP disconnects all your appliances and lights.
How many kW can you use at home? How much does it cost?
Available power in kW at home / Daily kW cost / Number of days / Total cost in billb) You pay for the electricity you use: the energy payment.(‘Consum’) This is a variable amount depending on how many kWh you really use. If you are on holiday, you don’t pay anything, except for the fridge...