Physics 7 Lesson 28: Practice Measuring amperage and voltage for parallel circuits
1. Summary of theory Tóm
1.1. Experiment target
- Knowledge: Know how to connect 2 light bulbs in series.
- Skills: Practice measuring and detecting the law of amperage and voltage in a circuit connected in series with 2 bulbs.
- attitude: Good sense in practice period.
1.2. Laboratory instruments
– Each group:
- 3V . Power Supply
- Two identical flashlight bulbs.
- 1 milli ammeter has a current of 0.5A and a current of 0.001 A
- 1 Voltmeter with current: 6V and DC: 0.1V
- 1 switch, lead
- Sample report of groups
- Side table to answer the prep questions.
1.3. Theoretical basis
- Xfirst, X2 … SHOCKINGn are electrical devices
- Ifirst, I2 … Print and IAB is the amperage through the electrical equipment and in the main circuit.
- Call UAB is the voltage at the two ends of the circuit.
- Ufirst, U2 … Un is the potential difference between the two ends of each electrical device, respectively.
– A parallel circuit is a circuit consisting of electrical equipment connected to each other to form turn circuits, which have the same starting point and the same end point.
- Figure 1.1 shows the X . devicesfirst, X2 … SHOCKINGn connected in parallel
a) Current in a parallel circuit:
– The current flowing in the main circuit is equal to the total amperage flowing in the electrical equipment (in the turn circuits).
- Formula: IAB = Ifirst + I2 +…+ In
– Measure the amperage through each electrical device, we use an ammeter connected in series with that circuit (or measure the amperage through each turn circuit) and then apply: IAB = Ifirst + I2 +…+ In
b) The potential difference between two ends of a parallel circuit:
- The potential difference between the two ends of a circuit consisting of devices connected in parallel is equal to the potential difference between the two ends of each electrical device (the two ends of each circuit turn):AB = Ufirst = U2 = … = Un
- To measure the potential difference between the two ends of each electrical device (each section of the circuit) or between the two ends of the circuit, we only need to use a voltmeter in parallel with the two ends of that circuit.
2. Practice report
* Fill in the blanks with suitable words or phrases:
a) Voltmeter is used to measure the potential difference between two points.
b) The (+) pin of the voltmeter is connected to the positive terminal of the power supply.
c) Ammeter used to measure amperage.
d) Connect the ammeter in series to the circuit so that its (+) pin is connected to the positive side of the power supply.
* Measure the voltage for the parallel circuit:
a) Draw in the box below a circuit diagram similar to figure 28.1a, in which there is an additional voltmeter connected to the two ends of bulb 2.
b) Measurement results:
The potential difference between the two ends of the lamps connected in parallel is equal and equal to the potential difference between the two common junctions Utwelfth = U34 = UMN.
* Measure amperage for parallel circuits:
a) Measurement result:
The main circuit current is equal to the sum of the bypass currents I: I = Ifirst + I2
Question 1: Electrical circuit diagram like figure:
a) Knowing that ammeter A shows only 5A, the current flowing through lamp 1 and lamp 2 is equal and equal to 1.5A. Determine the amperage through the lamp D3 and the amperage through the lamp D4.
b) The above circuit is connected to a power source with a voltage of 12V. Know that the potential difference between the two ends of the light bulb D2 is 4.5V. Find the potential difference between the two ends of the remaining bulbs.
Verse 2: Given amperage and voltage at the two ends of the lamp are shown as the graph of the figure below.
Based on this graph, determine:
a) The current through the lamp when applied to a voltage of 1.5V.
b) What is the potential difference between the two lamp heads if the current through the lamp is 100mA.
Question 3: Given the circuit as shown in the diagram. Close the lock K, ammeter A1 reads 0.1A, ammeter A2 reads 0.2A.
a) Calculate the ammeter reading A.
b) Replace the above power source with another power source, the ammeter A shows 0.9A. What is the number of ammeter A1, A2 now?
Verse 4: Given a power source, three identical light bulbs, a K-lock, a motor, and wiring.
a) Draw a circuit diagram in which all the devices are connected in series and the voltmeter measures the potential difference between the two motor ends, the ammeter measures the amperage in the circuit.
b) The voltage at both ends of the motor is 3V and at the ends of each lamp is 1.5V. Determine the voltage of the power source.
c) One lamp burned out, are the other lights on? What is the voltage difference at the ends of each lamp, motor and battery then?
Through the Practice of Measuring amperage and voltage for this parallel circuit, you need to complete some of the goals given by the lesson, such as:
State the relationship between amperage and voltages in a parallel circuit.
Connect a circuit consisting of two light bulbs in parallel and draw the corresponding diagram.
Determine experimentally the relationship between the amperage, the voltages in the parallel circuit.