Activity 5

Part 1: Some Properties of Electric Circuits

INTRODUCTION

Aim: To observe voltage and its nature in different types of circuits as well as its basic electricity relationships

Hypothesis:

1. The more the electrical source (battery), the greater the voltage will be

2. If the battery has bigger voltage, the light bulb will shine brighter

3. The more light bulbs added in a series circuit, the less bright they will be

4. The addition of light bulbs in a parallel circuit doesn’t affect brightness

5. Voltage is directly proportional to the current with a resistor

6. With a variable resistor, when resistance increase, current decreases

Theory Background:

An electrical circuit is formed by connecting components together.

Manipulative Variables:

1. Independent : Circuit type (parallel and series)
2. Controlled : Battery, voltage
3. Dependent : Voltage; brightness of light bulb; resistance

MATERIALS AND METHODS

List of Equipments:

• Laptop: To do the simulation
• Equipments in the simulation: battery, wire, amperemeter, switches

Procedures:

I. Observing Voltage Relationships

1. Go to the PHeT Circuit Construction Kit simulation

2. Drag out three batteries

3. Measure the voltage of each battery using the voltmeter and record the data

4. Measure the voltage of a combination of batteries by arranging the batteries in the figure above (1 and 2 combined, 1 and 2 and 3 combined) and then record the data

II. Using Voltage

1. Go to the PHeT Circuit Construction Kit simulation

2. Construct a circuit consisting of a battery and a lightbulb in the lifelike visual mode

3. Vary the voltage of the the battery and observe the brightness

III. Using Voltage in Series Circuit

1. Go to PHeT Circuit Construction Kit simulation

2. Construct a circuit with a bulb, a switch, a voltmeter, and an ammeter

3. Put the battery voltage to 12V

4. Measure the voltage of the battery and the current into it and the brightness of bulb

5. Add one more bulb, (2 bulbs) and repeat procedure 4

6. Add another bulbs (3 bulbs) and repeat procedure 4

IV. Using Voltage in Parallel Circuit

1. Go to the PHeT Circuit Construction Kit simulation

2. Construct a parallel circuit with a bulb, switch, voltmeter and an ammeter

3. Set voltage of battery to 12V

4. Record current and brightness of a bulb

5. Add one more bulb and repeat procedure 4

6. Add one more bulb and repeat procedure 5

V. Observing Voltage and Current Relationships With Resistors

1. Go to the PHeT Circuit Construction Kit simulation

2. Construct a circuit with a battery, ammeter, and resistor

3. Make the voltage of the battery vary

4. Record voltage of battery and the current in the circuit

VI. Observing Voltage and Current Relationships for Variable Resistors

1. Go to the PHeT Circulation Construction Kit simulation

2. Construct a circuit containing a battery, voltmeter, ammeter, and a resistor

3. Vary the value of the resistor at least ten times

4. Record in a table the resistance, current, and voltage for each ten trials

DATA COLLECTION

I. Observing voltage relationships

Battery	Voltage
1	9.0
2	9.0
3	9.0
1 + 2	18.0u
1 + 2 + 3	27.0

II. Using voltage

III. Using voltage in series circuits

Number of bulbs	Bulb ohm	Battery Voltage	Current into Battery	Brightness of Bulb
1	10 Ω	12 V	1.2 A	Bright
2	20 Ω	12 V	0.6 A	Not so bright
3	30 Ω	12 V	0.4 A	Not Bright

IV. Using voltage in parallel circuits

Number of bulbs	Bulb ohm	Battery Voltage	Current into Battery	Brightness of Bulb
1	10 Ω	12 V	1.2 A	Bright
2	5 Ω	12 V	2.4 A	Bright
3	3.3 Ω	12 V	3.6 A	Bright

V. Observing voltage and current relationships with resistors

Voltage	Current	Resistance
9 V	0.9 A	10 Ω
12 V	1.2 A	10 Ω

VI. Observing voltage and current relationships for variable resistors

Voltage	Current	Resistance
12 V	1.09 A	11 Ω
12 V	1.00 A	12 Ω
12 V	0.92 A	13 Ω
12 V	0.86 A	14 Ω
12 V	0.80 A	15 Ω
12 V	0.75 A	16 Ω
12 V	0.71 A	17 Ω
12 V	0.67 A	18 Ω
12 V	0.63 A	19 Ω
12 V	0.60 A	20 Ω

DATA PROCESSING AND PRESENTATION

I. Observing Voltage Relationships

1. Describe the relationship between the number of batteries and the voltage and explain what you think might be happening.

• The more the batteries, the more the voltage in which the total voltage of the circuit is the result of all the addition of all the voltage of each batteries.

II. Using Voltage

1. Draw what the circuit looks like.

2. How does the voltage of the battery compare to the light bulb voltage? Explain what you think is happening.

3. Think about a real light bulb and battery; explain what you think is happening that causes the changes in brightness.

• The change in brightness is because

III. Using Voltage in Series Circuits

1. Summarise the relationships you observed and explain what you think is happening.

• The more bulbs in the circuit, the less bright they will be because the current must be divided to light up more bulbs, hence it won’t be as bright as when the current is only used to light up one bulb.

2. Test to see if changing the battery voltage causes you to modify any of your conclusions. Explain what you measured and any conclusions you draw from your tests.
3. What happens when you take a wire out of a circuit? Explain what you think is happening.

• When one part is taken out, the whole circuit will no longer function, hence all the bulbs will shut down because the bulbs at the other end of the circuit won’t get the current.

4. Test using the voltmeter or ammeter in different ways. For example does it matter if you take the reading on the left or right of the battery?

IV. Using Voltage in Parallel Circuits

1. Summarise the relationships you observed and explain what you think is happening.

• In parallel circuit, the current is not divided for each bulb, so each bulb will get the same current that will light them up and the result is that all of them will be bright

2. Test to see if changing the battery voltage causes you to modify any of your conclusions. Explain what you measured and any conclusions you draw from your tests.
3. What happens when you take a wire out of a circuit? Explain what you think is happening.

• Contrary to series circuit, if one part is taken out, the rest of the bulbs will still light up because they do not share a path. Each of them have their own path and will remain to light up even if the other doesn’t.

4. Test using the voltmeter or ammeter in different ways. For example does it matter if you take the reading on the left or right of the battery?

• No

V. Observing Voltage and Current Relationship with Resistors

1. Explain what might be happening to cause the change in current.
2. How are current and battery voltage related? What is the shape of the graph?

• Directly proportional, the graph is straight at a constant elevation

3. Describe how you could use the simulation to verify the relationship. Test your ideas and make modifications to your original answers if necessary. Explain your reasoning.

VI. Observing Voltage and Current Relationship For Variable Resistors

1. Chart and determine the algebraic relationship for resistance and current.
2. Chart and determine the algebraic relationship for resistance and voltage.
3. Explain the relationship in terms what you think is happening in the circuit. Include how this experiment is like the one where you added light bulbs.

CONCLUSION

1. The hypothesis is correct in which the more the electrical source (battery), the greater the voltage will be, as shown from the results of the experiment, with one battery the voltage is all 9 V, but with 2 batteries, it is 18 V and with 3 batteries it is 27 V.

2. The hypothesis is correct in which the bigger the voltage, the brighter the light bulb will shine. If we see it in a reality situation, battery and lamp have its own life life span and it won’t last forever. Eventually, as time flies the brightness of the lamp will start to dim as the voltage and current is the batteries is decreasing. Due to it, the voltage and current of the lamp will decreases as well.

3. The hypothesis is correct in which the more light bulbs in the circuit, the less bright they will be because each of the bulb will get less current. A circuit with only one bulb, the bulb shines so bright, but with two bulbs, the shine decreases, and even less with three bulbs.

4. The hypothesis is correct in which the more light bulbs in a parallel circuit, the brightness won’t be affected, they will still be bright. The brightness of when only one bulb is put and when all three bulbs are attached is the same.

5. The more current flow in the circuit means the voltage is more, in which the shape of the graph will show a directly proportional relationship.

6. The hypothesis is correct in which when the resistance increase and voltage stay the same, the current decreases.

Part 2 : Resistors in Series and Parallel Circuits

INTRODUCTION

Aim: To observe basic electricity relationships in series circuits and in parallel circuits

Hypothesis:

1. In series circuit, the total resistance is the sum of all individual resistors and the total current is the same throughout while voltage is sum of all the volts in individual resistor

2. In parallel circuit, the inverse of the total resistance is equal to the sum of the inverses of the individual resistors. The voltage will always be the same while current differ.

Theory Background:

There are three basic circuit which are parallel, series and combined. In series circuit same current flow throughout the circuit but voltage will differ for each component in the circuit. In a parallel circuit, the voltage flowing through will always be the same and the current changes. Combined is basically just the combination of both parallel and series. The formula of resistance is R = V/I. Resistance equal to voltage over current.

Manipulative Variables:

1. Independent : Current, Voltage
2. Controlled : Voltage
3. Dependent : Resistance

MATERIALS AND METHODS

List of Equipments:

• Laptop: To do the simulation
• Equipments in the simulation: battery, wire, amperemeter, switches

Procedure:

I. Series Circuit

1. Go to PHeT Circuit Construction Kit simulation

2. Construct a circuit as shown in figure 1 on the sheet

3. Make the resistors have different value and record the value of each resistor

4. Use the ammeter moving it to take readings in the different places seen in figure 2 on the sheet

5. Use the voltmeter to take voltage readings

6. Calculate Resistance using Ohm’s law (V=IR) for the total resistance in last column.

II. Parallel Circuit

1. Go to PHeT Circuit Construction Kit simulation

2. Construct a circuit as shown on figure 1 on the sheet

3. Set the same value resistors as used in experiment 1

4. Take readings in different places shown in figure 2 on the sheet by moving the meters

5. Calculate total resistance using Ohm’s law

DATA COLLECTION

(i) Series Circuit

Resistor	Voltage (V)	Current (A)	Resistance
1	1.5	0.15	10
2	3.0	0.15	20
3	4.5	0.15	30
Total	9.0	0.15	60

(ii) Parallel Circuit

Resistor	Voltage	Current	Resistance
1	9.0	0.90	10
2	9.0	0.45	20
3	9.0	0.30	30
Total	9.0	1.65	5.45 ~5.5

DATA PROCESSING AND PRESENTATION

(i) Series Circuit

1. How is the total resistance related to the individual resistances? Total current to the individual currents? Total voltage to the individual voltages?

The total resistance is calculated by the sum of all of the individual resistors. The total current is the same in all around the circuit. The voltage is the sum of all the voltage in the individual resistors. There is only one path for the current to travel

2. Write a paragraph explaining what you think is happening in series circuits to cause the above relationships to occur.

There is only one wire connecting everything together. It means that everything flows through one wire giving it absolute control over the current. The current is all the same in one circuit because the circuit is not divided.

(ii) Parallel Circuit

1. How is the total resistance related to the individual resistances? Explain what you think is happening.

We need the individual resistance in order to find total resistance. The formula has been stated below (number 2). The inverse of total resistance is equal to the sum of the inverses of the individual resistance. There are a few path for current to travel.

2. Look up the mathematical relationship for finding the total resistance in a parallel circuit. Show that your data fits the equation

1/Req = 1/R1 + 1/R2 + 1/R3

This is the mathematical relationship to find the total resistance in a parallel circuit

1/Req = 1/10 + 1/20 +1/30

         = 3/20 + 1/30

         = 11/60

Req /1= 60/11

          = 5.45 ~ 5.5

Our data fits the equation well the result is the same as dividing the total voltage to the total current.

3. Summarize the similarities and differences between the series and parallel circuits. Include your reasoning about what you think is happening.

The similarities and differences between the series and parallel circuits is first the form is different. To differ parallel and series circuit you can basically identify them from the branches. If there are branches then it is a parallel circuit if there are no branches then it is a series circuit. In parallel circuit the voltage across each component. The total voltage of each components is the sum of the voltages across the components of a series circuit. The current in a parallel circuit is the total sum of the current from each component. In a series circuit the current that flows through each component is the same. If one component from a series circuit is not functioning very well then the series circuit overall will not work.

CONCLUSION

The hypothesis is correct because indeed the total resistance in a series circuit is calculated by the sum of all of the individual resistors. The total current is the same in all around the circuit. The voltage is the sum of all the volts in the individual resistors. This happens because there is only one wire connecting everything together. It means that everything flows through one wire giving it absolute control over the current. The current is all the same in one circuit because the circuit is not divided.

Part 3. Combo Circuit Lab

INTRODUCTION

Aim: To find out the effect of different arrangements of electrical components in a circuit to the current and voltage

Hypothesis: If the electrical circuit are arranged differently, then the current and the voltage will differ

Theory Background:

An electrical circuit is formed by connecting components together. Light bulb, power supply, resistor are components present in a circuit. They work together in order to achieve certain function, usually to start up a machine. Our house use parallel circuit so that something brokes not all components are damaged.

Manipulative Variables:

1. Independent : Circuit arrangement (figure A and figure B)

2. Controlled : Number of resistors

3. Dependent : The current, voltage, and resistance in circuit

MATERIALS AND METHODS

List of Equipments:

• Laptop: To do the simulation
• Equipments in the simulation: battery, wire, amperemeter, switches

Procedure:

1. Go to the PHeT Circuit Construction Kit simulation

2. Put three resistors on the work area. Right click on each to make the resistances different from one another. Make a data table like the one given and record the individual resistances.

3. Build the circuit given in Figure A.

4. Measure the voltage across each resistor and the power supply and measure the current through each resistor and the total current coming out of the power supply

5. Record the data in a table.

6. Do the same as procedure four for the circuit in figure B

DATA COLLECTION

Figure A - Power supply (battery) : 9 V

Resistor	Individual Resistance (ohms)	Current (amps)	Voltage (Volts)	Resistance in Circuit (R = V/I)
1	10	0.41	4.09	9.98 ~ 10
2	20	0.25	4.91	19.64 ~ 20
3	30	0.16	4.91	30.69 ~ 30
Total		0.82	13.91	60.31 ~ 60

Figure B - Power supply (battery) : 9 V

Resistor	Individual Resistance (ohms)	Current (amps)	Voltage (Volts)	Resistance in Circuit
1	10	0.30	3.0	10
2	20	0.30	6.0	20
3	30	0.30	9.0	30
Total		0.90	18	60

CONCLUSION

The different arrangement of circuit, as seen from the first arrangement (Figure A) and second arrangement (Figure B) does affect the current and the voltage. We can see that the current in figure B is quite larger than figure A by 0.08 amps. Even though both of the figures has the same voltage value for the battery and the resistors there are still differences in the total amount of voltage. We can see that the amount of voltage in Figure B is also larger than figure A by 4.09 volts. But when calculating the resistance we can see that the result of the resistance in the circuit is the same as the individual circuit value. So we can state that when a parallel circuit contains a series circuit in them it can cause larger amount of voltage and current compared to a separated series circuit and parallel circuit.