Ohms law Essay Example for Free

Ohms law EssayAn electronics factory needs resistors of 5 ohms and 15 ohms for a new electrical device. My task is to investigate how the vindication of a piece of outfit depends on duration and to unwrap the length of the telegraph needed to make the required resistors, using hardly 4 volts. Introduction/Planning A selection of different wires made from constantan and nichrome and the usual research lab apparatus allow be available 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 alloy whose resistance stays fairly constant when it becomes hot. In fact the resistance changes by less than 0. 5% even when the temperature rises by a few degree centigrade degrees. Nichrome, along with other metals, is an alloy whose temperature does change appreciably when it becomes hot. Before starting time my coursework, I swallow to find the var iables in the experiment, safety aspects etc. I found that a payoff 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 get hold of to make sure that these factors remain constant or excluded from the experiment. We are only investigating length merely the other variables may change our outcomes. In electricity, resistance is the ratio of the potential difference (p. d. or voltage) crossways a conductor to the electrical latest, which devolves through it as a result. The unit of measurement is the ohm (O), this being the resistance of a conductor requiring a potential difference of 1 volt across its ends to produce a sure of 1 ampere.For a given metal conductor at constant temperature the value is the alike whatever the period (Ohms law), but rises if the temperature rises. Any conductor possessing resistance gives off heat when a current flows through it. Joules law describe s this effect. Resistance occurs when the electrons travelling along the wire collide with the atoms of the wire. These collisions slow down the flow of electrons causing resistance. Resistance is a measure of how hard it is to move the electrons through the wire.Ohms law The current aerodynamic through a metal is comparative to the potential difference across it, provided that the temperature remains constant. We are dismissal to use 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 lot in accordance 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 heart of current menstruum in a locomote made up of pure resistances is directly proportional to the electromotive take up impressed on the circuit and inversely proportional to the total 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 vary current (AC), but additional principles must be invoked for the analysis of complex circuits and for AC circuits alike 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 separately element without division or branching into parallel circuits. When two or more resistances are in series in a circuit, the total resistance may be calculated by adding the value 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 incandescent 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 prohibit (-) ones to another conductor, so that each unit is, in effect, on a parallel branch. The value of two equal resistances in parallel is equal to half the value of the component resistances, and in every moorage 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 change currents, circuit components other than resistance must be considered. If a circuit has a number of unite 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 either junction in a circuit through which a steady current is flowing, the sum of the currents flowing to the point is equal to the s um of the currents flowing away from that point.The secant law states that, starting at each 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 there is an alternating current is complicate by the fact that capacity and inductance are always present.Inductance makes the peak value of an alternating current lag behind the peak value of voltage capacitance makes the peak value of voltage lag behind the peak value of the current. Capacitance and inductance inhibit the flow of alternating current and must be taken into account 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 defect on its measurement, so the way to work out the percentage error is Percentage error = (error / metric value) i 100 Conduction in metals In metals, atoms contain protons, nucleus and lose electrons which orbit more or less 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 additiond then the resistance will also increase as the electrons will have a longer distance to travel and so more collisions will occur. Due to this, the length increase shoul d 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 surface 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 bulk large because of their increase in energy.