I. Qualitative investigation of series and parallel circuits

An electrical circuit is composed of a completer closed path (or paths) for electric current. A "series" circuit has only one route for the power to follow. A "parallel" circuit has two or an ext paths because that the electricity.

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You will very first wire a basic circuit i beg your pardon will allow you to test materials for conductivity. Following some circuits will certainly be wired to demonstrate the impacts of collection and parallel circuits on materials in the circuit.



1. Affix your circuit board as indicated in the figure and also note that the bulb will certainly light as soon as you touch the probes together.

2. Touch the ends of another loose wire v the probes. Note that the bulb lights brightly. This is an indication of great electrical conductivity because the existing through the pear is straight related come brightness.

3. Check several various other items and also record her results. Include a coin, your skin, and a manufacturer of water. Be certain that the probes a re in call with the material being measured however not through each other. List the materials tested and your conclusions around their conductivity.

4. Rewire the circuit as presented in the chart below. Is this a series or parallel circuit?


5. Now remove wire #2 and connect that to pear #2. Connect one more wire from pear #2 to bulb #1. The number illustrates the circuit. Exactly how does the brightness of each bulb compare with that the the bulb in procedure step 4. Why is that different? Unscrew one bulb. What happens and also why?


6. Wire the circuit shown. Present on the diagram or top top a map out the path(s) of existing flow. Is this a collection or parallel circuit? Unscrew one bulb. Describe what happens and also why.

II. Quantitative examination of voltage, current, and Ohm"s law.

Electric current is the flowrate of electrical charge and also is measure up in amperes. The current transports electric energy along conductors. Voltage (V) is a measure up of power per unit charge between two point out in the circuit. One may think of voltage as the effective "pressure difference" which causes the current to flow. Resistance (R) is the opposition to current flow and also is measured in ohms. In practice, resistors take it the form of irradiate bulbs, toasters, heaters and also other devices which use electrical energy come perform valuable tasks and the undesirable type of resistance in electric wiring the transports the electrical energy come you.

Ohm"s regulation will be utilized in this laboratory exercise to determine the voltage, current, or resistance in a circuit. Ohm"s legislation simply says that the existing in a circuit is directly proportional come the voltage and inversely proportional come the resistance in the circuit:

or in symbol form

ns = V/R or equivalently R = V/I

Symbols and also instrumentation: The following symbols will certainly be offered in the circuit diagrams.


A wire offers essentially zero resistance in most handy circumstances.

The "battery" will be a connection on the activities tables to a main DC electric supply.

The very same laboratory meter will be offered for both the ammeter and voltmeter functions. Friend will need to select the correct duty with the selector switch.

An ammeter will constantly be wired in collection in a circuit. Fail to do this will an outcome in swollen fuses or damaged meters. Recall that the present has only one path to circulation in a series connection, for this reason the ammeter procedures the present that flows v the circuit elements which space in collection with it. The ammeters to be provided will measure in milliamperes or 10-3 amperes.

A voltmeter is constantly wired in parallel v the circuit elements it is testing and measures the voltage change throughout them.


(Proper labeling that the circuit diagrams is component of her report.)

A. Ohm"s Law

1. Cable up the circuit as shown with the ammeter in place, observing the exactly polarities. Collection your meter selector switch for DC milliamperes. The "battery" in this situation will it is in the round Flex lab receptacles on her lab table i beg your pardon are connected to a DC power supply - perform NOT use POWER till the circuit has actually been approved by the instructor.


2. After approval, use power by connecting the wires come the DC receptacles and also record the ammeter reading in milliamperes. Repeat the current measurement every of the other resistors through placing castle in the circuit in ar of the very first one.

3. Disconnect the strength leads and also remove the ammeter indigenous the circuit. Move it come DC volts and connect the in parallel throughout the resistor. Reconnect the DC voltage and also measure the voltage throughout the resistor. Repeat because that the other resistors.

4. Friend now have actually voltage and current dimensions for every resistor. Usage Ohm"s regulation to calculate the resistance for each resistor and also compare the calculation value acquired from the labeling ~ above the resistor or from the color code ~ above the resistor.

B. Distribution of Current.

1. Form the collection circuit shown below. Since you will certainly again be making use of the meter as an ammeter, reset that is selector switch to DC milliamperes. Make certain it is correct before applying power.

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2. Cable the ammeter successively in places 1,2 3 and 4 and record the current value in each location. Note that conventional existing is taken to be clockwise in this circuit, while the electrons will certainly be circulating counterclockwise. What deserve to you conclude about the existing in a series circuit from your measurements?

C. Circulation of Voltage

The circuit wired in part B will currently be used to measure up voltages. The relationships illustrated listed below will it is in used, but because you will be utilizing the same meter for an ammeter and a voltmeter, the ammeter will not it is in in location when you are measuring the voltages.


1. Measure the voltage across each resistor subsequently and across the entire circuit, as shown by V4. Record the results.

2. Compare the sum of voltages throughout the separation, personal, instance resistors come the voltage across the whole circuit. What deserve to you conclude about the voltage in a series circuit?

3. Use the voltages across each resistor obtained in step 1 over and the currents obtained from section B above, in addition to Ohm"s Law, to attain values because that the individual resistances. Compare the values with the given values for the resistors.

4. Indigenous the complete voltage measure up in action 1 and also the total current measure in ar B, calculate the tantamount resistance the the entire circuit created of the 3 resistors in series. Compare this result with the sum RA + RB + RC.


1. What attributes does a wire serve? are there insulators linked with her apparatus? What execute they do?

2. What, if anything, flows v the wires?

3. Why need to there be two connections to a battery and also to a light bulb?

4. If you have a 120 volt appliance and 2 amperes of present flow through it, what is the power supplied by it in watts? What is that resistance in ohms?

5. Why are your family receptacles wired in parallel fairly than in series?

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