Title: Laboratory Report on Investigating Series and Parallel Electric Circuits Aim: Investigate and demonstrate electric circuits in series and parallel Equipment : 4 electric cells of battery (each 1.5 volts) 2 Battery holder 8 crocodile cable 1 switch 1 Ammeter 2 light bulbs 1 switch Precautions : - Handle all the equipment with care and caution - Avoid parallax error when reading Ammeter - Make sure that there are no liquids (water in particular) near the electric circuits - Make sure your hand is not wet - Check the equipment carefully before use it - Don’t use broken equipments - Leave the switch open (turn off) when it is not being used Procedure : 1. Normal way/normal series : 1. Prepare a switch, a light bulb, a battery (2 cells in a battery holder), an ammeter, some cables 2. Connect all the equipment by connecting the battery to the switch with cable, then connect the switch to the lightbulb with cable. Connect the lightbulb to the Ammeter with cable, and connect the Ammeter to the battery with cable. 3. Check if the switch already closed so that the light bulbs can turn on 4. Takes note on the brightness and the ammeter 2. Normal parallel 1. Prepare a battery (2 cells in a battery holder), a switch, 2 light bulbs, 1 ammeters, some crocodile cables 2. Connect all the equipment. Create a series circuit first (Battery connects to switch, switch connects to lamps, lamps connects to ammeter, and ammeter connects to battery). Add another crocodile cable between the switch and lamps to connect the series circuit with a new lightbulb and then use another crocodile cable to connect the new lightbulb with the cable between lamp and ammeter 3. Check if the switch already closed so that the light bulbs can turn on 4. Takes note on the brightness and the ammeter 3. Series circuit with 2 light bulbs 1. Prepare a battery (2 cells in a battery holder), an ammeter, 2 light bulbs, a switch, some crocodile cables 2. Connect all the equipment by creating a series circuit (like the first setup) but we also add another light bulbs between the first light bulbs and the ammeter 3. Check if the switch already closed so that the light bulbs can turn on 4. Takes note on the brightness and the ammeter 4. Series with two batteries and one light bulbs 1. Prepare two batteries (4 cells and 2 battery holder), an ammeter, a light bulbs, a switch, some crocodile cables 2. Connect all the equipment by creating a series circuit (like the first setup) but we also add another battery between the first battery with the switch 3. Check if the switch already closed so that the light bulbs can turn on 4. Takes note on the brightness and the ammeter 5. Parallel with two batteries and two light bulbs 1. Prepare two batteries (4 cells and 2 battery holder), an ammeter, a light bulbs, a switch, some crocodile cables 2. Connect all the equipment by creating a simple parallel circuit (like the second setup) but we add another battery between the first battery and the switch 3. Check if the switch already closed so that the light bulbs can turn on 4. Takes note on the brightness and the ammeter Observation : Table of data about the current and the brightness of the light bulbs of every setup Set up Current Brightness of light bulbs Normal series circuit 0.2 A Not too bright and not too dim Normal parallel circuit 0.2 A Dimmer than series circuit Series circuit with two light bulbs 0.15 A Very dim Series circuit with two battery 0.3 A Very bright Parallel with two battery 0.3 A Very bright Normal series circuit Normal parallel circuit Series circuits with two light bulbs 4. Series circuit with two batteries 5 Parallel circuit with two batteries Discussion : Electric circuits are paths for transmitting electric current. An electric circuit includes a device that gives energy to the charged particles constituting the current, such as a battery or a generator; devices that use current, such as lamps, electric motors, or computers; and the connecting wires or transmission lines. Electric Current is the rate of flow of electrons in a conductor. The SI unit for current is Amperes (A). The device to calculate currents is called ammeters. We can calculate current using Current = charge/time. Voltage/potential difference is the external work needed to bring a charge from one location to another location in an electric field. Voltage uses volts as the unit measurement. Voltage can be calculated using a voltmeter. Resistance, on other hand, Is a measure of how difficult it is to push a current through a circuit. Resistance used Ohms (Ω) as its measurement unit. Resistance depends on the length and cross-sectional area of the conductor and temperature. Current, Voltages, and Resistance can be calculated using this formula : V is Voltage/Potential difference (V) I is Current (Amps) R is Resistance (Ohms) Electromotive force (e.m.f.) is the voltage (potential) that a battery will supply. Driving force that gives electrons the energy to move around the circuits. It is measured by volts. Electromotive force is used in a cell. In this experiment, we use 1.5 V cell or 3 V batteries (1 battery has 2 cells). There around. This is a table that summarized the voltage (Potential difference), current, and resistance pf 5 setup in this experiment : Setup Current Voltage/potential difference Resistance Normal series circuit 0.2 A 3 3/0.2 = 15 Ω Normal parallel circuit 0.2 A 3 3/0.2 = 15 Ω Series circuit with two light bulbs 0.15 A 3 3/0.15 = 20 Ω Series circuit with two battery 0.3 A 6 0.3/6 0.05 Ω Parallel with two 0.3 A 6 0.3/6 battery 0.05 Ω Electric circuits can be made into 2 types of circuits. Series and parallel circuit. If there are no branches, it is a series circuit. If there are branches, it is a parallel circuit. Serial Circuit : Serial circuit is an electric circuit in which the electric current passes through each circuit element in order. Open or close the switch in a series circuit at any point can cause the entire light bulbs in the serial circuit, start or stop operating. We can calculate current, potential difference, and resistance using this formula : Current : Current = I1 = I2 = I3 In series circuit, the current is the same for all the elements Voltage : Voltage = V1 + V2 + V3 In a series circuit, the voltage is the sum of the voltage drops of the individual components Resistance : Resistance = R1 + R2 + R3 The total resistance of two or more resistors connected in series is equal to the sum of their individual resistances The first, third, and forth setup is in series. In the first setup, the brightness of the light bulbs is bright but in the third setup, when we add another light bulb in a series circuit, the brightness is not as bright as the first setup. The reason is each light bulb carries the same resistance. If we put each other together, the total resistance increased. According to Ohm Law, if the total resistance increases and the voltage is the same, the current decreases. That’s why the brightness of the light bulbs are not as bright as the first setup. That is one of the disadvantages of a series circuit. In the forth setup, we add a new battery which has 3 volts. That makes the total voltages increase into 6 volts as we have 2 batteries in the circuit with 3 volts each. By increasing the voltage, the current will also increase. That’s why the light bulb is brighter than the first setup. Parallel Circuit Parallel Circuit is an electric circuit in which A parallel circuit comprises branches so that the current divides and only part of it flows through any branch. In a parallel circuit, if a lamp breaks or a component is disconnected from one parallel wire, the components on different branches keep working. And, unlike a series circuit, the lamps stay bright if you add more lamps in parallel. We can calculate current, potential difference, and resistance using this formula : Current : Current = I1 + I2 + I3 The total current is the sum of the currents through the individual components Voltage/Potential difference : Voltage = V1 = V2 = V3 In a parallel circuit, the voltage is the same for all elements Resistance : 1/RTotal = 1/R1 + 1/R2 + 1/R3 To find the total resistance of all components, add the reciprocals of the resistances of each component and take the reciprocal of the sum. Total resistance will always be less than the value of the smallest resistance The second and fifth setup is in parallel. In parallel, even if we have 2 or more light bulbs, the brightness is still the same because the current passes through each resistor the same and the light bulbs experience the same current. Conclusion : From this experiment, we know that in series circuits, if we add more light bulbs, the total resistance will increase and the current will decrease, but the voltage will be the same. That makes the brightness dimmer as the current passing through each light bulb is reduced. While, in a parallel circuit, the brightness appears the same, as the current passing through each light bulb is the same but the total current is increased.
