...metal wire, together with the physical dimensions of the wire, from which you will calculate the resistivity of the metal. Theory The resistance R of a component in a circuit is given by the equation V = IR where V is the potential difference across the component and I is the current in the component. The resistance of a wire is given by the equation R = ρl / A where ρ is the resistivity of the metal from which the wire is made, l is the length of the wire and A is its cross-sectional area. Using the circuit below, you will make measurements of current and voltage for different lengths of wire. You will plot a graph of resistance against length and from this you will calculate the resistivity. A V flying lead zero end of the metre rule tape to hold wire into place resistance wire 70 © University of Cambridge International Examinations 2006 Teaching AS Physics Practical Skills Resistivity of a wire Student Worksheet Making measurements and observations Use the micrometer screw gauge to measure the diameter d of the resistance wire in several places along the length. Each time you take a measurement at a new place, rotate the wire slightly. 1 Tape the wire to the metre rule so it cannot slip and the markings of the rule are visible. 2 Connect the circuit shown in the diagram above. The flying lead should have a bare conducting end and should be long enough to touch any part of the resistance wire. ...
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...In this investigation I am going to investigate what affect the resistance of a wire. Electricity flows in metals. Metal wires are made of millions of tiny metal crystals. Each crystal’s atoms are arranged in a regular pattern. The metal is full of ‘free’ electrons that do not stick to any particular atom. They fill the space between atoms in a metal. When these electrons move they create an electric current. Conductors have resistance, but some are worse than others. The free electrons keep bumping into atoms. A wires resistance depends on four main factors which are: Resistivity The length of the wire Cross sectional area The temperature of the wire I am going to investigate how the length of the wire affects the resistance. I have done a preliminary experiment to help me decide the best way to do my investigation. The results should also help me make a prediction. Preliminary Investigation Below are my results from the preliminary experiment (see table 1). I have taken three readings each from the Volts and current to make sure it is as accurate as possible Table 1 From the results I can see that as the length of the wire increases, the resistance increases as well. Furthermore I have noticed that if you double the length of the wire, the resistance is roughly doubled. E.g. when the length of the wire is 20cm the resistance is 3.14 ohms, when the length of the wire is 40cm the resistance is 6.18 ohms which is roughly double 3.14 ohms. In my main investigation...
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...Year 11 Physics Investigation- What factors affect the resistance of a wire? Introduction We are trying to find out if the thickness of a wire affects the resistance of a wire and also how it will do that. One reason I chose this investigation was because human reaction time is eliminated by not using the parachute method (the parachute experiment is to find out the factors affecting the rate of decent of a parachute), because you have to measure the timings on it by the eye and hand pressing the stop button and there could be some inaccuracies in this. In the test I am doing there is no space for human error because all the measuring is done by equipment and machines so all I have to do is make sure I use them properly and read them with accuracy. The wire resistance experiment is more precise because the equipment I will use to measure all sorts of different factors in the experiment is more precise than in the parachute experiment mainly because everything is still and not moving in the resistance experiment. We have chosen to do the thickness of the wire because it is easy to control and keep accurate because of the micrometer, which is very precise. In the parachute investigation I would have to measure the distances with a ruler and the micrometers precision is 0.01mm which is a very high precision whereas the ruler has a lower precision of 1mm. We could have used the material as a variable but when we get a graph of results it will be a bar chart...
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...the length of the wire affects the wires resistance. Also measuring the voltage and current. A thin and a thick wire are used to get the results needed. There are three factors that influence the resistance of w wire which are, the thickness of a wire, temperature and length. Knowing those factors and measuring them will show how the experiment went. Introduction: ------------------------------------------------- The resistance of a material is the extent to which is oppose the flow of current. “Electronics for today or tomorrow, 2nd Edition, Tom Duncan, page 8” Where as conductors have low resistance and inductors have high resistance. Further more resistance is measures with ohms. The main concept of the experiment is to investigate the difference in the resistance when having several lengths of a wire. The reason why different lengths of a wire affect the resistance is because the length of the will is increased which will also make the resistance increase as well, therefore electrons will have a longer distance to travel. Because of this the length of a wire should be proportional to the resistance. Conductors are good metals of electricity because they have low resistance which is why electrons get away easily just by applying the voltage. Furthermore, the resistance of a wire and the length of the wire both increase but the thickness of the wire decreases at the same time. Moreover, thin wires have high resistance but thick wires have low resistance. Due to Ohm’s law which...
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...IB Higher Physics Internal Assessment Candidate Name: Aleksei Kuryla Candidate Number: Title: resistivity of nichrome |D |DCP |CE | | | | | DATA COLLECTION AND PROCESSING | |Criteria |( |Mark |Comments | |Aspect 1 |Raw results only shown | | | | | |Correct units | | | | | |Uncertainties shown | | | | | |Uncertainties justified | | | | | |Uncertainties to 1 sig fig | | | | | |Decimal places consistent with uncertainty | | | | |Aspect 2 |Processed...
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...Wire Resistance and Ohm’s Law PhET MiniLab Introduction: When an electrical potential exists in a circuit, a current may flow. Current is the flow of electrons in a circuit. Resistance in the circuit slows the flow of the electrons, reducing the current in the circuit. We will use the mathematical form of Ohm’s Law frequently when we investigate electric current and circuits later in this unit. Additional Material Needed: Clean Drinking Straw Procedure Part I Wire Resistance: • Blow through the drinking straw. • Cut the drinking straw in half and blow through a half-straw. • Describe the effect of length on ease to blow air through the straw. There is more resistance when the straw is longer. • Cut the halves again in half. • With the four pieces, blow through one, then blow through all four made into a larger, square-shaped straw. • Describe the effect of straw size (diameter) on ease to blow air through the straw. Less resistance • Now, open the PhET Simulation Electricity, Magnets, and Circuits ( Resistance in a Wire[pic] As wire length (cm) increases, the resistance (Ω) INCREASES As wire area (cm2) increases, the resistance (Ω) DECREASES As wire density (Ωcm) increases, the resistance (Ω) STAYS THE SAME Procedure Part II: Ohm’s Law: Electricity, Magnets, and Circuits ( Ohm’s Law [pic] mA is milliamps, and 1000 milliamps equals one Ampere. • Move the potential (volts) and resistance (ohms) sliders and observe the current (amps) As voltage increases...
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...3.1 Project methodology Bonding of permanent join of metallic parts to form an electrically conductive path that ensures electrical continuity and capacity to conduct safe current. Grounding is vital to connect the metallic parts of an electrical appliances to the earth (ground) by using thick conductor wire with very low resistance for safety purposes. In other word, grounding is a connection of the neutral point of a power supply system to the earth to avoid danger during discharge of electric energy. Hazards that may occur due to failure of earthing system are electrocution, fire or explosion due to the leakage of current through undesired path and to ensure potential current carried by conductor does not rise with respect to the earth...
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...and different types of transmission lines. A TRANSMISSION LINE is a device designed to guide electrical energy from one point to another. It is used, for example, to transfer the output rf energy of a transmitter to an antenna. This energy will not travel through normal electrical wire without great losses. Although the antenna can be connected directly to the transmitter, the antenna is usually located some distance away from the transmitter. On board ship, the transmitter is located inside a radio room and its associated antenna is mounted on a mast. A transmission line is used to connect the transmitter and the antenna. The transmission line has a single purpose for both the transmitter and the antenna. This purpose is to transfer the energy output of the transmitter to the antenna with the least possible power loss. How well this is done depends on the special physical and electrical characteristics (impedance and resistance) of the transmission line. In an electronic system, the delivery of power requires the connection of two wires between the source and the load. At low frequencies, power is considered to be delivered to...
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...through a given cross section of the wire in a time, then the current through the wire is I = q/t. * Where: q is in COULOMBS, t is in SECONDS and I is in AMPERES (1A = 1C/s). * BATTERY * A battery is a source of electrical energy. * If no internal energy losses occurs in the battery then the potential difference between its terminals is called the ELECTROMOTIVE FORCE (emf) of the battery. * The unit for emf is the same as the unit for potential difference, the VOLT. * RESISTANCE * The resistance of wire or other object is a measure of the potential difference that must be impressed across the object to cause a current of one ampere to flow through it. * R = V/I * The unit of resistance is OHMS (Ω), 1Ω = 1V/A. * OHM’s LAW * Ohm’s Law originally contained two parts. * The defining equation for resistance, V = IR, also stated the R is a constant independent of V and I. * The relation V = IR can be applied to any resistor, where V is the potential difference between the two ends of the resistor, I is the current through the resistor, and R is the resistance of the resistor under those conditions. * GEORG SIMON OHM * 1787-1854 * A high school teacher in Cologne and later a professor at Munich * Formulated the concept of resistance and discovered the proportionalities expressed in * MEASUREMENT OF RESISTANCE BY AMMETER AND VOLTMETER * A series circuit consisting of the resistance to be measured, an ammeter, and...
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...THE POTENTIOMETER: Internal Resistance of a Test Cell OBJECT To calibrate a one meter slide wire potentiometer using a standard cell and then to use this potentiometer to measure the emf of a test cell. The terminal voltage of the same test cell is then measured as different load resistors are connected across the test cell and these data are used to determine the internal resistance of the test cell. THEORY The electromotive force (emf) of a cell is its terminal voltage when no current is flowing through it. The terminal voltage of a cell is the potential difference between its electrodes. A voltmeter cannot be used to measure the emf of a cell because a voltmeter draws some current from the cell. To measure a cell's emf a potentiometer is used since in a potentiometer measurement no current is flowing. It employs a null method of measuring potential difference, so that when a balance is reached and the reading is being taken, no current is drawn from the source to be measured. Figure 1. This is the basic circuit diagram for a potentiometer. Point C is the sliding contact which can be adjusted for zero current deflection through the galvanometer. In this method (refer to Figure 1) a uniform, bare slide wire AB is connected across the power supply. If you were to connect a voltmeter between the + power supply terminal and point A you would measure essentially zero volts. If you were to now connect the voltmeter between the + power supply and point B you would measure...
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...44) 1. A proton beam in an accelerator carries a current of 125 A. If the beam is incident on a target, how many protons strike the target in a period of 23.0 s? 2. A copper wire has a circular cross section with a radius of 1.25 mm. (a) If the wire carries a current of 3.70 A, find the drift speed of the electrons in this wire. 3. An aluminum wire having a cross-sectional area equal to 4.00 10–6 m2 carries a current of 5.00 A. The density of aluminum is 2.70 g/cm3. Assume each aluminum atom supplies one conduction electron per atom. Find the drift speed of the electrons in the wire. 12. A lightbulb has a resistance of 240 when operating with a potential difference of 120 V across it. What is the current in the lightbulb? 13. An electric heater carries a current of 13.5 A when operating at a voltage of 120 V. What is the resistance of the heater? 18. Aluminum and copper wires of equal length are found to have the same resistance. What is the ratio of their radii? 19. If the magnitude of the drift velocity of free electrons in a copper wire is 7.84 10–4 m/s, what is the electric field in the conductor? 21. If a certain silver wire has a resistance of 6.00 at 20.0°C, what resistance will it have at 34.0°C? 22. A certain lightbulb has a tungsten filament with a resistance of 19.0 when at 20.0°C and 140 when hot. Assume the resistivity of tungsten varies linearly with temperature even over the large temperature range involved here. Find the temperature...
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...between voltage, current, and resistance. Go to ⎝Battery-Resistor Circuit. Click on the green “Run Now” button. The simulation should look like the picture to the right. 1. Change the resistance and voltage. Observe what happens to the current. Note the relationship you observed between each of the following: (direct, inverse, none) a. resistance and current = _indirect_______________________ b. voltage and current = direct__________________________ Go to ⎝Ohm's Law. Click on the green “Run Now” button. The simulation should look like the picture to the right. 2. What is the current through a resistor with the following resistances? Let voltage = 6 V a. R = 100 ohms I = _60__ mA(current) b. R = 300 ohms I = 20____mA(current) 3. Now, determine the current through the wire with the following volts. Let resistance = 500 ohms a. Volts = 3 V I = 6___mA(current) b. Volts = 6V I = 12____mA(current) 4. Think about the formula (V=IR), does this make sense according to this formula? Explain! (Be sure to include the relationship between resistance and current, and the relationship between voltage and current in your answer) Yes, it does make sense according to the formula (V=IR). In question 2 where the voltage was set at 6V, the current was higher when the resistance was 100 ohms than when the resistance was 300 ohms. This is due to...
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...For our project we decided to disassemble and understand a Memphis 1 Channel Mono Block Amplifier. First we started by disassembling the amp down to the main circuit board. From there we assigned ourselves different components to understand what they were and how they worked inside the amp. We all researched our components and got back together to discuss and figure out the flow of power and operations of the amp worked. A general idea of what the amp does is as follows. Power comes into the inputs from the positive side of the car battery. A negative source comes from the car’s chassis to the negative terminal. The remote wire comes in from the head unit or source of sound to the remote input. When the source turns on, power runs from the remote wire to a relay inside that allows power to run through. Power then runs to various capacitors to store up power before running to the inductor that converts the power to usable power for the MOSFETs. As the power runs through the circuit, it eventually comes to resistors which slow up the current flow. Sound comes in through the inputs and to the MOSFET amplifiers. Then sound goes to the sound dampeners to clean the sound waves up before going to the sound outputs. To better understand the amp and its components we will branch off and explain each of the components and what they do. When a relay receives power, power runs through a set of coils and creates a magnetic field that actuates an arm inside and closes the circuit...
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...surrounding temperature gets too high, the alloy melts and allows the spring contact mechanism to break the circuit. Unlike electrical fuses or circuit breakers, thermal fuses only react to excessive temperature, not excessive current, unless the excessive current is sufficient to cause the thermal fuse itself to heat up to the trigger temperature. Important properties and why: The fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics. The metal strip or wire melts at a lower temperature than the wire and other components in the rest of the circuit. Fuse elements may be supported by steel or nichrome wires, so that no strain is placed on the element, but a spring may be included to increase the speed of parting of the element fragments. The fuse element may be surrounded by air, or by materials intended to speed the quenching of the arc. The material that the part is made from: A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by a non-combustible housing. The fuse is arranged in series to carry all the current passing through the protected circuit. One mechanism is a small melt able pellet that holds down a spring. When the pellet melts, the spring is released, separating the contacts and breaking the circuit. The manufacturing method: A machine cuts notches in a long silver strip that...
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...Lab #3: Controlling Currents 09/18/13 Objective- The first objective in this lab is to determine how a light bulb behaves in different circuit arrangements. The second objective investigates how the voltage across the light bulb varies with the amount of current through it. Finally, the last objective is to explore how the length of a wire affects resistance. Procedure- Activity 1 A) Measure the voltage across an open-circuit cell by connecting the positive terminal of the voltmeter to the positive terminal of the call and the negative terminal of the voltmeter to the negative terminal. The voltage across cell #1 is 1.462 V. The voltage across cell #2 is 1.455 V. B) Measure the voltage across two cells connected in a series. The voltage across two cells is 2.9 V. C) Connect the circuit as shown in the diagram below. Insert two D-cells into the circuit. D) What is the effect of rotating the knob on the device that is identified as a “Potentiometer”? Rotating the potentiometer adjusted the brightness of the light bulb. Activity 2 A) Set the multimeter to the 200/400 mA range. Connect the circuit as the same in activity one with the ammeter in the circuit. Set the second multimeter to the VDC scale and connect its leads across the bulb. B) Read the current that is flowing through the bulb. Measure the voltage across the bulb. Record both values in the data table below. C) Turn the knob of the potentiometer and increase...
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