Internal Resistance of a cell
Topic: Internal Resistance of a cell Aim: To measure the internal resistance and emf (the potential differences across a voltage Source when no current is flowing) and to observe the combination of cells Hypothesis: The emf of the old cell is less than the emf of the new cell but the internal resistance of the old cell is much greater than the new cell. Introduction: Resistance in electricity, property of an electric circuit or part of a circuit that transforms electric energy into heat energy in opposing electric current. Resistance involves collisions of the current-carrying charged particles with fixed particles that make up the structure of the conductors. Resistance is often considered as localized in such devices as lamps, heaters, and resistors, in which it predominates, although it is characteristic of every part of a circuit, including connecting wires and electric transmission lines. (Britannica.2006) The dissipation of electric energy in the form of heat, even though small, affects the amount of electromotive force, or driving voltage, required to produce a given current through the circuit. In fact, the electromotive force V (measured in volts) across a circuit divided by the current I (amperes) through that circuit defines quantitatively the amount of electrical resistance R. Precisely, R = V/I. Thus, if a 12-volt battery steadily drives a 2-ampere
Measurement of the resistivity of Nichrome
Measurement of the Resistivity of Nichrome (NiCr) Introduction In this coursework, I am going to measure the resistivity of Nichrome. Nichrome is a non-magnetic alloy of nickel and chromium. It is a good conductor of electricity and heat, and has a high melting point. Due to its relatively high resistivity and resistance to oxidation at high temperatures, the wire made of Nichrome is widely used in heating elements, such as in hair dryers, electric ovens and toasters. What does Resistivity mean? Resistivity (also known as electrical resistance) is a measure of how strongly a material opposes the flow of electric current. It is normally static and could be varied by changing the temperature. In general, resistivity of metals increases with temperature, while the resistivity of semiconductors decreases with increasing temperature. High values of resistivity imply that the material making up the wire is very resistant to the flow of electricity. Low values of resistivity imply that the material making up the wire transmits electrical current very easily. The unit of resistivity is the ohm meter (? m). The resistivity ? (rho) of a material is given by > ? is the static resistivity (measured in ohm metres, ?·m); > R is the electrical resistance of a uniform specimen of the material (measured in ohms, ?); > L is the length of the piece of material (measured in
Sensing project
Sensing project Project brief A new greenhouse is being developed for gardeners who are concerned about overheating plants in their current greenhouses. The new greenhouse has been built with opening windows but occasionally the windows of the greenhouse slips fully open and allow all of the trapped heat in the greenhouse to escape quickly. This is a major concern for serious gardeners. The test is to develop a sensing circuit that will sense whether the windows are fully open, so a gardener can be alerted of the problem. Introduction To begin we must know what a sensor is. A sensor is an electrical component, which produces a signal in response to alteration in its surroundings, this maybe an alteration in a physical variable or by movement of objects. The sensor planned for the sensing circuit ensuring the windows are not fully open is a rotary potentiometer. A rotary potentiometer is a component, which has three terminals. When the angle of rotation is changed on the component's arm then the potential difference (often called voltage) is also changed. Once the voltage reaches a specific point a separate circuit could activate an alarm showing that the window has slipped and is fully opened. The potential difference is the difference between potential energy between two separate points. Alternatively a different sensing circuit could be used. A circuit with
investigating the relationship between the diameter and the current in a wire at its melting point
Investigation Report Aim Theory Electrical resistance is a measure of the degree to which an object opposes the passage of an electric current. The SI unit of electrical resistance is the ohm. Its reciprocal quantity is electrical conductance measured in siemens. Resistance is the property of any object or substance of resisting or opposing 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. Some formulae for resistance are where R is the resistance of the object / ? V is the potential difference across the object / V I is the current passing through the object / A (Ref. http://en.wikipedia.org/wiki/Electrical_resistance) where R is the resistance/ ? ? is the resistivity / ?m l is the length of the wire / m A is the cross section area of the wire / m A = ?() = ? where A is area / m d is the diameter / m Putting the formulae together, so (Ref. http://physics.bu.edu/~duffy/PY106/Resistance.html) Aim of investigation The aim of this work is to investigate the relationship between the resistance and the diameter of the wire. Variables Variable Independent / Controlled / Dependent Resistance D Resistivity C Length of wire C Diameter I Prediction Since the theory suggests that So So the resistance should be
Electrical Hazards.
Electrical Hazards, risks of injury or death arising from exposure to electricity. Electricity is essential to daily life, providing heat and light and powering appliances in homes and factories. It must, however, be treated with great care, because the consequences of an electrical fault can be serious and sometimes fatal. Generally voltages greater than 50 volts can present a serious hazard and currents of more than about 50 milliamps flowing through the human body can lead to death by electrocution. A shock occurs when a "live" part of some device is touched, so that current passes through the body. Its severity depends on many factors, including the body's conductivity (the ease with which electricity passes through it). The conductivity is usually small, but can be increased if the body or clothing is wet. The risk of injury also increases according to the size of the voltage or current, or the duration of contact. There is a risk of electrocution (death by electric shock) if current passes across the heart. For example, if one foot is touching wet ground, the risk is greater if the arm on the opposite side touches a high-voltage source than it would be if the arm on the same side did so. Current passing into the body generates heat, which burns the tissue. Electricity can also present less direct risks. Burns are caused when hot surfaces on electrical appliances are
Power generation
Introduction: Oil is a liquid fossil fuel and is formed from layers and layers of buried animals and plants that have been under a lot of heat and pressure over a long time. Oil is a non-renewable resource as it cannot be produced on human time frame. Oil is used for many things; it's used for transportation, heating purposes, fuel for electricity generating plants. Fuel is found underground reservoirs. The production of electricity from oil begins with the extraction of oil and ends with the oil burning in boilers and turbines at power plants. Crude oil is removed from the ground by drilling deep wells and pumping it up to the surface. The crude oil is then moved to a refinery (refineries remove a portion of the impurities in the oil, e.g. metals) where it is refined into a number of fuel products: kerosene, gasoline, liquefied petroleum gas (propane). Then this crude oil is moved to power plants by trains, trucks, pipelines or ship. Many methods are used at the power plants to generate electricity from oil. One of the methods is to produce steam by burning the oil in the boilers which is used by a steam turbine to generate electricity. Another common method is to use combustion turbines to burn oil. In a fossil plant, oil, gas or coal is fired in the boiler, which means that the chemical energy of the fuel is converted into heat. Name of Fuel
Determining Avogadro's Number Lab
Determining Avogadro's Number Lab Data Collection Table 1. Table showing initial mass, final mass and qualitative observation of copper electrodes. Electrode 1 Electrode 2 Initial Mass (g) ±0.005 g 5.77 5.80 Final Mass (g) ±0.005 g 6.27 5.27 Observations The copper electrode is shiny after being placed in copper sulfate. It also appears to have become thicker. The copper electrode is dull after being placed in copper sulfate. It also appears to have become thinner and rusty. Table 2. Table showing current of copper electrodes in 600 second intervals. Time (seconds) ±5 seconds Current (amps - A) ±0.05 A 0 .1 600 0.7 200 0.9 800 .0 Note: As both copper electrodes were placed in a single beaker of copper sulfate, the data obtained for the current is the same for both electrodes. Thus, the "Current" column in Table 2 represents the current of both copper electrodes. Table 3. Table showing voltage used during the experiment. Voltage (volts) ±0.5 V 6 Data Processing Moles: Number of moles Electrode 2, which lost 0.53 grams after being placed in copper sulfate, contains approximately 0.00834 moles of copper. Uncertainty of moles Uncertainty of mass = Uncertainty of initial mass + Uncertainty of final mass Uncertainty of mass = 0.005 g + 0.005 g Uncertainty of mass = 0.01 g Percent uncertainty of mass = Percent
Experiment: Decay of Charge in a Capacitor
Physics(AL) TAS Laboratory Report Experiment: Decay of Charge in a Capacitor Content A. Objectives B. Theories and Hypothesis C. Experimental Design D. Results and Data Evaluation E. Error Analysis F. Summary and Conclusions G. Possible Improvements A. Objectives The objective is to investigate the decay of charge in a capacitor when it discharges through a constant resistance. The discharge processes of two identical capacitors connected in series or parallel are also investigated. From the results obtained, determine the relations between discharge rate, capacitance and resistance. B. Theories and Hypothesis Theories about Decay of charge Consider a capacitor with capacitance C charged up by a potential difference V, connected across a resistor with constant resistance R. (Figure 1) At any time t, let VR and VC denote the potential difference across R and C respectively, I denotes the current through R, Q denotes the charge remained in C. By Kirchhoff's Laws, Hence, When . Hence Q0 is the initial charge in capacitor. Practically, the charge in a capacitor cannot be measured easily at any time. Therefore current, instead, can be measured. At any time, Or, , where I0 is the initial current through the resistor. Therefore theoretically, it is known that the decay of charge through constant resistance follows an exponential decay pattern. That is, the
Investgating resistivity - Planning and Implementing
This investigation aims to test the relationships within the formula R= ?l/A, resistance in ohms equals resistivity in ohm metres multiplied by length divided into cross-sectional area, and to find a value for the resistivity of constanton (how strongly constanton opposes the flow of an electrical current), ?. I aim to find two values for ?, one to be obtained through an experiment, and the other to be obtained using data books. By obtaining and comparing these two values, I hope to find a reliable and realistic value for constanton's resistivity. Plan of Investigation Apparatus List Just over a metre length of constanton wire, between 0.2mm and 0.4mm in diameter, to be attached using sellotape to a metre rule, calibrated in mm. Variable resistor, 0-12? Digital Ammeter, 0-10 A, +/- 0.005 A Digital Voltmeter, 0-20 V, +/- 0.005V Leads Pair of crocodile clips Micrometer Power pack, supplying 0-2 V, direct current The experiment - Plan First, the metre of constanton wire must be straightened to allow it to be measured accurately. The diameter of this wire should then be measured, using the micrometer. (The zero error of the micrometer must be measured first, to ensure that the value for the diameter is as accurate as possible). Measure the diameter in three places, then compare these results. If they are not equal (to within experimental error) measure the wire's
viscosity of golden syrup
An Investigation to Measure the Viscosity of Golden Syrup. Aim: - the aim of my investigation is to measure the viscosity of golden syrup and see if this value depends upon the temperature of the syrup. Apparatus not included in diagram: - micrometer, 5 ball bearings as provided by the school, stop clock, magnet, marker pen, metre rule, weighing scales, thermometer, water bath. (The measuring cylinder is 50 cm3) Certain aspects have to be taken into account to ensure that the experiment is carried out safely. These are: - o If heating the syrup, be careful not to burn yourself on hot equipment. o Goggles should be worn to prevent syrup from entering the eye. Variables that need to be considered are:- the size of the ball bearing to be dropped, the temperature of the syrup, the amount of syrup used, the length that the distance travelled is measured over, the depth beneath the top that the speed and distance are measured from, the type of syrup used and the density of the syrup. I have decided to change the size of the ball bearing to see how this effects viscosity and a further study will be done changing the temperature of the syrup. The differing size ball bearings will be dropped at a constant temperature. To make this a fair test I will have to keep all other variables the same. To do this I will:- o Keep the amount of syrup used, the type of syrup (golden)
