Ohm’s law Essay

An electronics factory unavoidably resistors of 5 ohms and 15 ohms for a new electricalal device. My task is to analyse how the opposite of a piece of wire depends on length and to take chances the length of the wire needed to make the required resistors, using yet 4 volts. Introduction/Planning A selection of different wires do from unbrokenan and nichrome and the usual laboratory apparatus will be open for me. wire A Constantan wire of approximate diameter 0. 3mm Wire B Constantan wire of approximate diameter 0. 4mm Wire C Constantan wire of approximate diameter 0.3mm A constantan is an deprave whose defense stays fairly constant when it becomes hot. In fact the resistance diverges by less than 0. 5% even when the temperature rises by a a couple of(prenominal) hundred degrees. Nichrome, along with new(prenominal) metals, is an every(prenominal)oy whose temperature does change appreciably when it becomes hot. sooner first my coursework, I have to find the varia bles in the experiment, safety aspects etc. I found that a number of things affect the resistance of a wire. Below is a list of factors and reasons why they affect the resistance of a wire.From this list of factors I have to make sure that these factors remain constant or excluded from the experiment. We argon only investigating length but the other variables whitethorn change our outcomes. In electricity, resistance is the ratio of the potential residual (p. d. or potential) across a theater director to the electrical catamenia, which flows by means of it as a result. The unit of measurement is the ohm (O), this being the resistance of a theater director requiring a potential difference of 1 volt across its ends to leaven a up-to-the-minute of 1 ampere.For a given metal conductor at constant temperature the quantify is the same whatever the current (Ohms law), but rises if the temperature rises. Any conductor possessing resistance gives off heat when a current flows throug h it. Joules law describes this effect. Resistance occurs when the electrons travel along the wire collide with the atoms of the wire. These collisions slow down the flow of electrons causation resistance. Resistance is a measure of how hard it is to move the electrons through the wire.Ohms law The current flowing through a metal is comparative to the potential difference across it, provided that the temperature remains constant. We atomic number 18 going to spend metals, which obey ohms law, metals which give us a constant value for resistance (gradient). Resistance (? ) = P. d across the wire (V) / Current through the wire (A) Current flows in an electric circuit in agreement with several definite laws. The basic law of current flow is Ohms law, named for its discoverer, the German physicist Georg Ohm.Ohms law states that the amount of current flowing in a circuit made up of pure resistances is directly proportional to the electromotive force impressed on the circuit and inv ersely proportional to the make sense resistance of the circuit. The law is usually expressed by the formula I = V/R, where I is the current in amperes, V is the electromotive force in volts, and R is the resistance in ohms Ohms law applies to all electric circuits for both direct current (DC) and alternating current (AC), but spare principles must be invoked for the analysis of complex circuits and for AC circuits also involving inductances and capacitances.A series circuit as on page 5, is one in which the devices or elements of the circuit are arranged in such a way that the entire current (I) passes through each element without character or branching into duplicate circuits. When two or more resistances are in series in a circuit, the total resistance may be calculated by adding the values of such resistances. If the resistances are in parallel, the total value of the resistance in the circuit is given by the formulaIn a parallel circuit, electrical devices, such as in beard escent lamps or the cells of a battery, are arranged to allow all positive (+) poles, electrodes, and terminals to be joined to one conductor, and all negative (-) ones to other conductor, so that each unit is, in effect, on a parallel branch. The value of two equal resistances in parallel is equal to fractional the value of the component resistances, and in every case the value of resistances in parallel is less than the value of the smallest of the individual resistances involved.In AC circuits, or circuits with varying currents, circuit components other than resistance must be considered. If a circuit has a number of interconnected branches, two other laws are applied in order to find the current flowing in the various branches. These laws, discovered by the German physicist Gustav Robert Kirchhoff, are known as Kirchhoffs laws of networks. The first of Kirchhoffs laws states that at any junction in a circuit through which a steady current is flowing, the centre of the current s flowing to the point is equal to the brotherhood of the currents flowing away from that point.The plump for law states that, starting at any point in a network and following any closed path back to the starting point, the net sum of the electromotive forces encountered will be equal to the net sum of the products of the resistances encountered and the currents flowing through them. This second law is simply an extension of Ohms law. The application of Ohms law to circuits in which in that respect is an alternating current is complicated by the fact that capacity and inductance are always present.Inductance makes the peak value of an alternating current lag female genitalia the peak value of voltage capacitance makes the peak value of voltage lag behind the peak value of the current. Capacitance and inductance restrict the flow of alternating current and must be taken into bill in calculating current flow. The current in AC circuits can be determined graphically by means of vectors or by means of the algebraic equation, in which L is inductance, C is capacitance, and f is the frequency of the current.The quantity in the denominator of the fraction is called the impedance of the circuit to alternating current and is sometimes represented by the letter Z then Ohms law for AC circuits is expressed by the simple equation I = V/Z. We know that all instruments have an delusion on its measurement, so the way to work out the percentage error is Percentage error = (error / measured value) i 100 Conduction in metals In metals, atoms postulate protons, nucleus and lose electrons which orbit around the nucleus. Below, I have investigated conduction in metals and how they affect resistance.METAL LATTICE (Electrons move in a random direction. ) METAL LATTICE (Electrons with power pack in a particular direction. ) Variables Length If the length of the wire is increased then the resistance will also increase as the electrons will have a longer distance to travel an d so more collisions will occur. overdue to this, the length increase should be proportional to the resistance increase. Thickness If the wires thickness is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through.Due to this increased space between the atoms, there should be fewer collisions. The number of free electrons changes from one material to another. The sizing of the ions changes from one material to another, this affects the current and therefore affects the resistance. The arrangement and size of the atoms change from one material to another. So if there is a kink in the wire this will change the thickness of the wire. Temperature If the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy.