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
Investigating the forces acting on a trolley on a ramp
Physics coursework Investigating the forces acting on a trolley on a ramp Contents Page 3 -> Method Page 4 -> Theory Page 7 -> Results Page 9 -> Error Page 18 -> Appendixes Method The aim of the investigation was to investigate the forces acting on a trolley as it rolled down a ramp, and also to investigate the factors which may contribute to the results. To do this, a trolley and a ramp set at a variety of angles of incline were used, and then, using a light gate, the speed at which the trolley was moving when it passed through the light gate was calculated. The variables were the starting distance of the trolley in relation to the light gate and the angle of the ramp. Firstly, the equipment was set up as in fig. 1. The trolley was then run down the ramp with a piece of card attached to the side. This card was of a known length and could hence be used to calculate the velocity at which the trolley was moving. While the light gate did actually calculate the velocity, it only gave the answer to 2 decimal places, whereas it gave the time to 2 decimal places. Furthermore, the light gate calculated the velocity with the assumption that the card was exactly 100mm, whereas when the card was actually measured, this was a value closer to 102mm (±0.5mm). Next, after the trolley had passed through the light gate, the information from that 'run' appeared
Physics coursework; Finding the focal length of a lens using a graphical method.
Physics coursework; Finding the focal length of a lens using a graphical method. Planning: Firstly the rough focal length of my lens will need to be found to assist me in my real experiment. A simple way to do this would be, to hold the lens up to a flat white wall opposite a window when it is light outside, by moving the lens closer/ further away from the wall until an upside down image of objects outside the window (e.g. trees,) is produced, I can estimate an focal length for the lens which provides me with the minimum distance of (u), this saves time that would be spent trying to find a point from which I can begin measurements. The equipment will be set up as shown below: Apparatus: * Light source connected to a power pack * Wire grid (object) * 1m ruler (correct to the nearest mm) * a small bi-convex lens * a white 2D screen (approx 100*70 mm) ==> When the light is turned on the light will pass through the mesh creating an image which can be focused by the lens on the screen. ==> It is important to remember that light bulbs will get hot, so precautions should be taken to ensure I am safe from burns during the experiment. ==> It should also be considered that any experiment involving electricity carries risk so due care must be taken when handling any electrical equipment. ==> The light source will be covered with a sheet of grease proof paper, this will
Mobile Phones - A curse or a boon?
Mobile Phones - A curse or a boon? Since the beginning of time man has been inventing things; the bike, the car, the radio, the television, the telephone, the computer but the most recent invention to have taken the world by storm has to be the mobile phone. Originally a large, heavy, black box with an even larger protruding aerial, mobile phones were not widely used but today they are a must-have fashion accessory, and with coloured fascias, aerials, covers, logos and ring-tones available, its no surprise that children as young as eight are now asking Santa for an Ericsson PF768 or Motorola Wing Timeport V.550. With recent advances in technology WAP services have been provided on mobiles and in Japan they have fitted a video camera into the ever decreasing in size hand held phenomena. It is safe to say that mobiles have taken over, making it impossible to travel without hearing a dull-tone version of the number 1 tune blasting in your ear followed by, "Hello? I'm on the train!" There are many stories of lives being saved when someone suffers a heart attack whilst in the middle of nowhere and the victim is rescued because their companion rang the emergency services on their mobile. This is one reason why so many people own mobiles - security. The young and old are reassured that by owning a mobile, help can be on its way in the touch of a button if an emergency situation
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
Determination of the acceleration due to gravity (g)
Determination of the acceleration due to gravity (g) By-nanding Li Introduction Gravity is the force at which the earth attracts objects towards it; also know as the weight of objects. When objects fall towards the earth, their acceleration increases because of the gravity. This acceleration due to gravity is dependent on the object's mass. A free falling object, if gravity s the only force acting on an object, then we can know the object will accelerate at a rate of 9.81ms-2 down toward the centre of the earth, this is known as acceleration due to gravity and is given the symbol 'g'. We can find the force causing this acceleration using: F = ma And weight for the object: G = mg Where the 'm' is the mass of object and 'g' is the acceleration due to gravity. However, acceleration due to gravity is not the same through out the universe. The moon has a smaller acceleration due to gravity than the earth. If we were to drop a stone on the moon, it would fall more slowly. This does not mean the mass of the stone is changed from the earth to the moon, this means the moon has less attraction to the stone and the acceleration due to gravity on the moon is about on-sixth of that on the earth: g moon = 1.6 ms-2 In this investigation, I am going to determine the acceleration due to gravity on the earth by using an electronic timer and varying its height of dropping.
Microscopes. Using electrons instead of light means that the illumination has a much shorter wavelength than light.
Microscopes Cells can be seen with a light microscope but many structures within a cell - organelles - can only be seen clearly with an electron microscope. That is partly because an electron microscope has a greater magnifying power. However, increasing only magnification has its limits because at some point magnification reveals nothing more - the details only look bigger and vaguer. Magnification is how much bigger a sample appears to be under the microscope than it is in real life. Overall magnification = Objective lens x Eyepiece lens Using electrons instead of light means that the illumination has a much shorter wavelength than light. This is good because minute detail can be detected. We say that an electron microscope has a bigger resolving power than an light microscope Resolution is the ability to distinguish between two points on an image. The resolution of an image is limited by the wavelength of radiation used to view the sample. This is because when objects in the specimen are much smaller than the wavelength of the radiation being used, they do not interrupt the waves, and so are not detected. The wavelength of light is much larger than the wavelength of electrons, so the resolution of the light microscope is a lot lower. The actual resolution is often half the size of the wavelength of radiation used. Thus, for the light microscope the maximum
