Measurement of Electrical Resistance and Ohm’s Law
Physics Lab 204.001



Yewande Adeniyi
9/22/2011

PROCEDURE
1. Connect the ammeter A, the voltmeter V, and the power supply PS to the Resistance Box. The basic circuit supply is series with a resistor. To measure the current in the resistor, the ammeter is placed in series. To measure the voltage across the resistor, the voltmeter is placed in parallel. 2. Vary the current through resistor R1 in steps of .125A to .500A. For each specified value of the current, measure the voltage across the resistor and record the values in Data Table 1. The resistors will heat up and may be damaged by allowing current in them for long periods of time. Measurements should be made quickly at each value of the current. APPLY VOLTAGE ONLY WHEN DATA ARE BEING TAKEN. 3. Repeat Step 2 for each of the 5 resistors. For each resistor the ammeter must be in series with that resistor and the power supply, and the voltmeter must be in parallel with the resistor. Record all values in Data Table 1. 4. Connect the first Resistance Box to the second Resistance Box to measure the equivalent resistance of the combination. Use two values of current, 0.250A AND 0.500A, and measure the value of the voltage for each of these values of current. Record the voltage in Data Table 2. 5. Measure the voltage across the combination of R1 and R2 in series for currents 0.250A AND 0.500A and record the values in Data Table 2. 6. Connect Resistance Box 1 and 2 in parallel and measure the voltage across the combination for currents value of 0.250A and 0.500A and record in Data Table 2. APPARATUS
...Submission
INSTRUCTOR: ENGR. JAY S. VILLAN, MEPEE
Introduction
A multitester or multimeter is a device which can be used to gather data about electrical circuits. A basic multitester can measure resistance, voltage, and continuity; while more advanced versions may be able to provide additional data. This tool can be very useful to have around the house, and anyone who plans on doing electrical repairs should most definitely use a multitester for safety reasons. Multitesters can be used with the current off or on in most cases, although using the device with the current on can sometimes result in damage to the device.
Theory
Ammeters are employed for measuring current in a circuit and connected in series with the circuit. As ammeter is connected in series, the voltage drop across ammeter terminals should be as low as possible. This requires that the resistance of the ammeter should be as low as possible. The current coil of ammeter has low current carrying capacity whereas the current to be measured may be quite high. For this reason a low resistance is connected in parallel to the current coil.
Voltmeters are employed to measure the potential difference across any two points of the circuit these are connected in the parallel to the circuit. The resistance of voltmeter is kept very high by connecting a high resistance in series of the voltmeter with the...
...
Ohm’sLaw
Lab Report Number Three
Quyama T. Wheeler
@02669651
Partner: Munah Kaye
Amber Frazier
Objective: To demonstrate Ohm’slaw and to determine the resistance of a given resistor.
Theory: Ohm’slaw is the assertion that the current through a device is always directly proportional to the potential difference applied to the device. Electric current is the moving of charges from a higher potential to a lower potential. Wires of different material (a copper wire versus a silver wire, for example) will produce different currents, even if applied the same potential difference. This phenomenon, this characteristic respectful to each type of material is known as resistance.
Apparatus:
two multimeters (set on the 20mA and 20 V scale)
unknown resistor board
Extech instruments (018 Volts) Power Supply
Procedure: A circuit connecting the resistor board, the voltmeter and the milliammeter is assembled. The 20 milliampere range is selected on the ammeter and the 20V on the voltmeter. The power cord is then plugged into an electrical outlet and the unit is turned on. The experiment begins at 15 volts. The voltage and current are both recorded and these steps are repeated successively in two volt increments. A graph of I as a function of V is plotted and fit with a straight line, the slope of...
...Physics
Practical Report:
Experiment: Ohmic Resistance and Ohm’sLaw
Patrick Doan
Mr Sadowsky
11 PHYS 71
12/9/08
Table of contents
1.0 Aim 1
2.0 Hypothesis 1
3.0 Materials 1
4.0 Method 2
5.0 Results 3
 5.1 Qualitative Observations 3
 5.2 Data 34
6.0 Discussion 5
7.0 Conclusion 6
8.0 Bibliography 7
9.0 Acknowledgements 7
1.0 Aim:
To find out how current, voltage and resistance in a circuit are related, also to discover the relationship known as ‘Ohm’sLaw’.
2.0 Hypothesis:
In this experiment, conductors are used. Conductors which obey Ohm’sLaw are called Ohmic conductors. Thus, for an ohmic conductor, a graph of V (Voltage) verses I (Current) is a straight line passing through the origin. A conductor that does not obey Ohm’sLaw is called a nonohmic conductor.
Ohm’sLaw:
3.0 Materials:
• Power Pack 12V
• Voltmeter
• Light bulb
• 9 Alligator clips
• Ammeter
• Test tube
• Switch
• Multimeter
Patrick Doan 1
4.0 Method:
1. Collect all equipment and make sure the surface is clean and not wet
2. Wrap the nichrome wire around the testtube to form a coil
3. Use the multimeter to measure the...
...OHM’SLAW
INTRODUCTION
Ohm'slaw states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them provided the temperature remains constant.
The mathematical equation that describes this relationship is:
where V is the potential difference measured across theresistance in units of volts; I is the current through the resistance in units of amperes and R is the resistance of the conductor in units of ohms. More specifically, Ohm'slaw states that the R in this relation is constant, independent of the current.
The law was named after the German physicist Georg Ohm, who, in a treatise published in 1827, described measurements of applied voltage and current through simple electrical circuits containing various lengths of wire. He presented a slightly more complex equation than the one above (see History section below) to explain his experimental results. The above equation is the modern form of Ohm'slaw.
In physics, the term Ohm'slaw is also used to refer to various generalizations of the law originally formulated by Ohm. The simplest example of this is:
where J is the current...
...Knowledge
Resistance, in electricity, is a property of any object or substance to resist the flow of an electrical current. The quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage applied to the circuit. The resistance of an object is determined by the nature of the substance of which it is composed, its resistivity, accounting for its dimensions and its temperature. Resistivity is expressed in terms of Ohms / cm3 at 20ºC. An electrical conductor is any material that offers little resistance to the flow of an electric current. The difference between a conductor and an insulator, which is a poor conductor of electricity, is one of degree rather than kind, because all substances conduct electricity to some extent. A good conductor of electricity, such as silver or copper, may have a conductivity billions of times as great, or more, as the conductivity of a good insulator, such as glass or mica.
Method
We were set the task of investigating the factors that come into play when determining the resistance of a piece of wire. We would be provided with the necessary apparatus needed to carry out the investigations. The basic setup would involve a circuit with a set of cells connected in series with an ammeter and the piece of wire being investigated, and a voltmeter connected in parallel...
...affecting the resistance of a wire in an electrical circuit. Many factors will have to be investigated prior to experimentation. A prior knowledge of electrical circuits and the factors of resistance will be required. The conclusive objective will be that research on the subject matter is proven by experimentation.
Resistance
The standard opinion of resistance when electricity is concerned is the ability of a substance to resist the flow of electricity through it. Good conductors are associated with low resistance and poor conductors are associated with high resistance. As resistance is responsible for the current that flows, a high resistance will be responsible for a low current and a low resistance will be responsible for a higher current.
This is definition of resistance given by Hutchinson’s Encyclopaedia:
“In physics, that property of a conductor that restricts the flow of electricity through it, associated with the conversion of electrical energy to heat; also the magnitude of this property. Resistance depends on many factors, such as the nature of the material, its temperature, dimensions, and thermal properties; degree of impurity; the nature and state of illumination of the surface; and the frequency and magnitude of the current. The SI unit of...
...Voltage: Ohm'sLaw and Kirchhoff's Rules
ABSTRACT
Ohm'sLaw and Kirchhoff's rules is fundamental for the understanding of
dc circuit. This experiment proves and show how these rules can be applied to
so simple dc circuits.
INTRODUCTION
In the theory of Ohm'sLaw, voltage is simply proportional to current as
illustrated in the proportionality, V=RI. As shown in this relation, V
represent voltage which is the potential difference across the two ends of a
electrical conductor and between which an electric current, I, will flow. The
constant, R, is called the conductor's resistance. Thus by the Ohm'sLaw, one
can determine the resistance R in a DC circuit without measuring it directly
provided that the remaining variable V and I is known.
A resistor is a piece of electric conductor which obeys Ohm'sLaw and
has been designed to have a specific value for its resistance. As an extension
of the Ohm'sLaw, two more relationship can be drawn for electric circuits
containing resistors connected in series or/and parallel. For resistors
connected in series, the sum of their resistance is, RTOTAL=R1+R2+ ..... +Rn .
And for resistors connected in parallel, 1/RTOTAL==1/R1+1/R2+ ..... +1/Rn .
Complex dc circuit involving a combination of...
...Conclusion
Ohm'sLaw states that V=RI where V is the difference of potential at the poles of the element (measured in volts), R is the resistance of the element being tested (a resistor in this case, measured in ohms), and I is the current passing through the circuit (measured in milliamps). When the Yintercept on the attached voltage drop vs. current in the conductor graph is examined, it is observed that the the ranges of R values overlap, also the expected yintercept value of 0 falls between the maximum and minimum deviation. By further examining the graph,it is possible to notice that the plot of the voltage drop across the conductor versus the current in the conductor results in a straight line. Furthermore, the origin (0,0) is within experimental error for the yintercept of the graph. Both these statements show that the tested resistor verified Ohm'sLaw since theoretically the yintercept should be 0 and the voltage drop across the conductor versus the current in the conductor should be directy proportional. This can be concluded by observing the equation which is y = .054492x ± 0.0016x .0254 ± 0.10.
This laboratory had few causes of error that could significantly affect results. The most important factor was a mildly fluctuating power supply (the indicated current did not remain perfectly stable after being adjusted). Another possible cause of error is the possibility of misreading the...
{"hostname":"studymode.com","essaysImgCdnUrl":"\/\/imagesstudy.netdnassl.com\/pi\/","useDefaultThumbs":true,"defaultThumbImgs":["\/\/stmstudy.netdnassl.com\/stm\/images\/placeholders\/default_paper_1.png","\/\/stmstudy.netdnassl.com\/stm\/images\/placeholders\/default_paper_2.png","\/\/stmstudy.netdnassl.com\/stm\/images\/placeholders\/default_paper_3.png","\/\/stmstudy.netdnassl.com\/stm\/images\/placeholders\/default_paper_4.png","\/\/stmstudy.netdnassl.com\/stm\/images\/placeholders\/default_paper_5.png"],"thumb_default_size":"160x220","thumb_ac_size":"80x110","isPayOrJoin":false,"essayUpload":false,"site_id":1,"autoComplete":false,"isPremiumCountry":false,"userCountryCode":"US","logPixelPath":"\/\/www.smhpix.com\/pixel.gif","tracking_url":"\/\/www.smhpix.com\/pixel.gif","cookies":{"unlimitedBanner":"off"},"essay":{"essayId":35153251,"categoryName":"Mathematics","categoryParentId":"19","currentPage":1,"format":"text","pageMeta":{"text":{"startPage":1,"endPage":3,"pageRange":"13","totalPages":3}},"access":"premium","title":"Measurement of Electrical Resistance and Ohm\u0027s Law","additionalIds":[17,16,184,7],"additional":["Literature","Law","Law\/Intellectual Property","Education"],"loadedPages":{"html":[],"text":[1,2,3]}},"user":null,"canonicalUrl":"http:\/\/www.studymode.com\/essays\/MeasurementOfElectricalResistanceAndOhms796253.html","pagesPerLoad":50,"userType":"member_guest","ct":10,"ndocs":"1,500,000","pdocs":"6,000","cc":"10_PERCENT_1MO_AND_6MO","signUpUrl":"https:\/\/www.studymode.com\/signup\/","joinUrl":"https:\/\/www.studymode.com\/join","payPlanUrl":"\/checkout\/pay","upgradeUrl":"\/checkout\/upgrade","freeTrialUrl":"https:\/\/www.studymode.com\/signup\/?redirectUrl=https%3A%2F%2Fwww.studymode.com%2Fcheckout%2Fpay%2Ffreetrial\u0026bypassPaymentPage=1","showModal":"getaccess","showModalUrl":"https:\/\/www.studymode.com\/signup\/?redirectUrl=https%3A%2F%2Fwww.studymode.com%2Fjoin","joinFreeUrl":"\/essays\/?newuser=1","siteId":1,"facebook":{"clientId":"306058689489023","version":"v2.9","language":"en_US"}}