The Resistance of a lead Graphite line.
The Resistance of a lead Graphite line A measurement of lead graphite will be measured out on a piece of a4 paper I will be measuring the length and width of the strip of graphite I will draw out, I will be using a 2B pencil to make the experiment fair, I will also be using grid paper to make the measurements more precise. I will start at having a twenty-centimetre line by one centimetre line however I will be widening the length and width of the line and I will read the ohmmeter on every centimetre of the graphite line that I move the two jockeys to measure the resistance of the carbon track using the 20k settings to measure in mega ohms. I will take reading from every one centimetre three times in order two find the average and so to make it a fair test. I will be using jockeys in order to control the distance in which the current will flow. I will also use an ohmmeter once I have connected it to the carbon track so that I can use the results it shows and take them down. I am doing this experiment to find how variable the resistance is in the carbon track depending on length and width. The factors affecting my experiment will be the length and width so theses will be the two factors I will be placing my results on. Spreading electrons so the longer the carbon track or distance the more the electrons will spread causes resistance. Also the wider the carbon track the more
Measuring weight with a strain gauge.
Measuring weight with a strain gauge A strain gauge is a wire which is used to measure strain by the change in its resistance when it gets either longer and thinner or shorter and thicker. They are attached to a surface for which the strain is wanted, and need to be able to move as if they are part of the surface. Modern strain gauges are etched onto foil because its thin and flexible, and therefore able to move with the surface. Gauges are glued onto the test object with superglue so that they move as if they are a part of the object. Elastic modulus = stress/strain (When stress is a linear tensile or compressive stress, the elastic modulus is called Young's modulus). A tensile strain will be accompanied by a reduction (and compressive strain by an increase) in lateral dimensions. The ratio of the lateral strain to the longitudinal strain is called Poisson's ratio1. For most materials the value is between 0.25 and 0.4, and written as a positive number although the signs of the lateral and longitudinal strain are always opposite. The gauge factor of a strain gauge (G) = (?R/R)/(?l/l) where R = resistance and l = length. Since ?l/l is the strain (e) in the object which the gauge is attached to this can be written as ?R/R = eG, which means that the fractional change in resistance of the gauge is proportional to the strain in the object. To
The aim of our investigation is to investigate Ohms Law.
Siobhan Higgins G.C.S.E Science Coursework AT1 Aim- The aim of our investigation is to investigate Ohms Law. Introduction- In my investigation I am trying to prove that Ohm's law works. Ohm's law is used to find a value in a missing circuit. Georg Ohm, a German physicist proved that resistance is equal to voltage divided by current. Resistance is the difficulty in getting the current round the circuit. I will test the resistance of different lengths of nichrome wire. Prediction and Hypothesis I predict that the wider apart the crocodile clips are, the higher the resistance is. I know this as the longer the wire, the more free electrons there are, which means more collisions, which results in higher heat loss. Method- To make the test fair I need to repeat the test five times, and make sure I get accurate results. I will have to make sure that the crocodile clips are placed on the same spot for each try, I will do this by using a metre rule. To make this a safe test I will have to keep all wires and equipment neat. I will have to make sure that the desk is tidy. Between writing results I will have to switch the power pack off at the plug. I will have to make sure that I keep hair tied back, and make sure I don't touch the wire In the experiment I am going to measure the current, voltage and resistance, and the length of the wire, In the experiment I am
Aim To build and test a temperature sensor and analysing its suitability as a bath water thermometer.
Physics Sensing Coursework - Temperature sensor Aim To build and test a temperature sensor and analysing its suitability as a bath water thermometer. Introduction In making a temperature sensor the circuit and individual components need to be thought about. Also I need to find a way of measuring my sensor to calibrate its voltage output with the temperature it's measuring. First of all I require a component in my circuit which will change its electrical properties in the changing of temperature. This component is called a thermistor and there are two types; * The positive temperature coefficient thermistor or PTC thermistor has an increased resistance as temperature increases. These can be used as current limiters or in place of a fuse. Current through the device causes some resistive heating. If the current is too large the resistance increases due to heat increase and the current is reduced. * The negative temperature coefficient thermistor or NTC thermistor has a decreased resistance as temperature increases. Deciding on which of these to use in my circuit isn't a problem because both will change with temperature change just one has its resistance changed opposite to the other in temperature change. However there are some thermistors which are not suitable for this type of temperature measurement. Many PTC thermistors are of switching type, which means that their
Physics industrial visit
Supertram Introduction: Sheffield's Supertram is a vast network of tracks linking the whole city together. The Sheffield supertram is run by stagecoach. The supertrams employ many aspects of physics in there day to day running I am going to discuss two of these namely regenerative breaking and Three Phase power supply: The trams are supplied with electricity through the series of overhead cables which run above all the tracks. The trams then utilise a three phase power supply of 3x 380 V, 100Hz, 13kVA and a DC supply of 24 V, 5kW these originate in the 12 substations that are spread around the city at different maintenance points. The three phase power supply is an alternating current supply with 3 voltages operating at 120° out of phase (see below). All the currents have identical wavelengths and frequencies just out of phase. Having a three phase supply means the trams are supplied constantly with maximum power. The nature of three phase supply and the great deal o detail requires means it is expensive to install as various expensive components are required namely the converters that are needed. Although the initial costs are high the system is incredible in the way it increases the efficiency as the amount of power per amp for example a standard single phase 120/240 volt supply at 100amps would provide around 18000-26000 watts whereas a three phase supply with the
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
Ohm’s Law Investigation
Ohm's Law Investigation Introduction: In the following experiment, I predict that the filament bulb in which we are testing, on will not obey ohm's law. Their are many factors which make me believe this, such as the temperature of the bulb. If the filament bulb DID obey Ohm's Law, then the temperature would remain constant, meaning there would be resistance. When I think of a light shining, the temperature does not stay the same. Therefore I believe that the light bulb will not obey Ohm's law. The formula for Ohm's law is: RESISTANCE = pd or R = V current I The current through a wire is proportional to potential difference (voltage across the wire) providing the temperature does not change - (which I predict it shall). CHANGE IN TEMPERATURE = CHANGE IN RESISTANCE To make this a fair test, I must keep a close watch of the readings. I will include a trial run to make sure everything goes to plan. I will record the results 3 times - so I can be certain that we are exact in the experiment. SAFETY:To prevent any electric shocks, it is important that we wash our hands thoughly, so no water reaches the wires. We must also check our readings on the Voltmeter - incase any explosion occurs, and we must check that the wires are carfully fixed in to place. It is also important, for long hair to be tied up and to wear
To find out what happens in the filament of a bulb as we increase the voltage through the bulb.
Physics Investigation Aim: To find out what happens in the filament of a bulb as we increase the voltage through the bulb. I am carrying out an experiment to find the different resistances and currents created by a light bulb at different voltages. Because of the nature of a light bulb, it glows white-hot when fully on, the resistance will change at different voltages. When the voltage is low and the bulb is not very bright, it won't be as hot and therefore it will have less resistance. But when the current is high and the bulb is brighter, it will have a high resistance. I will be using the following circuit for the experiment: Definitions: Ammeter: This is a device that measures the current of electrons in Amps. It has to be placed in series on the circuit. Voltmeter: This is a device for measuring the potential difference of the electrons in the circuit. They are measured in Volts. It is placed in parallel. To use the circuit, I will take readings from both the ammeter and the Voltmeter. I will need to try and get results that are high and ones that are low, and try to have an even distance between each result. I will take down the readings from both the ammeter and the voltmeter. I should end up with 36 results, three results from twelve different voltage settings, hopefully all evenly spaced. The resistance is greater when the light bulb is hotter, because when
I am going to investigate the factors that affect how well graphite coated paper conducts electricity. Graphite Paper is paper coated with graphite on one side; it is a semi-conductor.
I am going to investigate the factors that affect how well graphite coated paper conducts electricity. Graphite Paper is paper coated with graphite on one side; it is a semi-conductor. I will be investigating how the width of the graphite paper affects the current and the resistance. I will also be investigating how the temperature of the graphite paper affects the resistance. The resistance of a conductor is defined by: - R = V is p.d across paper I is current through paper A current only flows between two points if the electrical potentials at the two points are different. The higher the potential difference at one point, the faster the current will flow between them. If the two points have equal electrical potentials, no current will flow between them. Just imagine the wire to be a plank of wood; and the current to be a ball. If there is no potential difference between the two ends of the plank, the ball will not roll to either side. If the potential of one side of the plank is made bigger, the ball will roll towards the other side. The more the potential on one side is increased, the faster the ball will roll to the other side. There are some variables I will have to keep constant throughout my two experiments, in order too keep it a fair test. When changing the width of the paper, the variables I will have to keep constant are: - . The length of the
Physics - Rotary Potentiometer
Can a Rotary Potentiometer be used as a conventional scale? Introduction I wanted to find out how a rotary potentiometer could be utilized to work as a weighing scale. The specific interest is the accuracy of this method and distinguish the advantages and disadvantages of using digital readings instead of our common everyday analogue spring gauge balance at the local supermarket. This investigation will require a potentiometer device being loaded with a series of masses which are linked to a voltmeter measuring the differences in voltage as more masses are added while a spring is used to hold the weight. The benefit of this system is that it can be calibrated in imperial and metric measurements as the results appear in Volts, whereas modern scales only provide 'grams' or 'kilograms' as opposed to pounds. Accuracy is vital in this task as there is a challenge to see how effective a potentiometer can be, with most spring scales can be accurate up to + or - 1g. Apparatus > 6V Battery pack (4 'D-sized' batteries), for ease of use and more energy efficient that a 12v mains power supply > Rotary potentiometer, attached to a DIY MDF wheel which rotates. It has a spring attachment hole at one end and a mechano shaft for attaching weights > Expendable Spring, an attachment unit to keep the rotating apparatus together, and the main unit holding weight of equipment > Digital
