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Electric Resistance

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The  electrical resistance  of an  electrical  conductor is a measure of the difficulty to pass an  electric current through that conductor. A conductor has free electrons randomly moving inside. When electric potential is applied to it, the electrons collide with other atoms and molecules of the conductor. The atoms and molecules create the obstruction in the flow of electrons. This obstruction is called resistance. Each and every material possesses the property of resistance because every conductor has atoms or molecules which can obstruct flowing electrons. If the material has less electrical conductivity, it means resistance of that material is high. So conductor like copper, gold, etc. has less resistance while insulators like wood, glass, etc. has higher resistance. Unit of resistance: Unit of resistance is ohms and it is denoted by Ω. Laws of resistance Value of resistance is directly proportional to length of the conductor and inversely proportional to area of
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Electric batteries

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Cells are devices that convert chemical energy to the electrical energy. Battery is a collection of one or more cells whose chemical reactions create a flow of electrons in a circuit. Batteries offer a way to store electrical potential energy in a container. One of the biggest advantages of batteries is that they are portable. Without batteries, our mobile phones would be connected to wire all the time like old telephones.                          Symbol of battery Battery has three basic components and they are anode, cathode and electrolyte. Anode is the negative side while cathode is the positive side. Don’t worry anode is positive terminal and cathode is negative terminal. But anode has dense electrons or negative charge carriers in electrochemical cell and thus said to be negative side while cathode has dense positive charges and said as positive side. Electrolyte is a substance that reacts with anode and cathode and creates a source of electrons. Construction
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Conductance, Resistivity and Specific resistance

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Conductance, resistivity and specific resistance are the properties of electric conductor or any other material. They all can be understood by resistance. Resistance is the amount of obstruction in the flow of current. Means resistance is the obstruction in flow of electrons. All these properties of material can be understood by resistance and also all these properties are dependent on value of resistance of that material. Conductance Conductance is an expression of the ease with which electric current flows through a material. Thus, conductance is a measure of how easy it is for electrons to flow through a material. As you all know resistance is the obstruction in the flow of electrons. So mathematically, conductance is the reciprocal of resistance. Conductance = 1 / Resistance The greater will be the resistance, the less the conductance and smaller will be the resistance, greater would be the conductance. If the resistance of material A is half than material B. Then,
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Ideal power source vs Practical power source

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A source is a device which converts mechanical, chemical, thermal or some other form of energy to electrical energy. The types of sources available in the electrical network are voltage source and current source. Voltage source is used to provide voltage to the load while current source is used to apply current. Voltage source A voltage source is device which provides constant voltage to load at any instance of time and is independent of the current drawn from it. This type of source is known as ideal voltage source. Practically ideal voltage source cannot be made. It has zero internal resistance. It is denoted by this symbol. The graph of voltage vs time represents the change in voltage of the voltage source with respect to time. It is constant at any instance of time. Voltage sources that have some amount of internal resistance are known as practical voltage source. Due to this internal resistance, voltage drop takes place. If the internal resistance is high, l
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How to measure current using Ammeter

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Current is the measure of the rate of flow of electric charges across the conductor. It is measured in the unit of Ampere. This current is most commonly measured by ammeter. Ammeter Ammeter measure the electric current in the circuit. The name is derived from the SI unit of electric current, ampere. To measure electric current in a circuit, ammeter must be connected in series because in series connection, ammeter experiences the same amount of current that flows in the circuit. Ammeter is designed to work with small fraction of volt. So voltage drop must be minimal. Symbol of Ammeter The capital A represents the ammeter in the circuit. How to use an ammeter Before we start measuring current, we will first set the ammeter range. Keeping the range to highest will prevent the ammeter to blow up its internal fuse. Then set the current type i.e. DC or AC. Now connect the terminals of ammeter in series of the resistance or load. By this arrangement, ammeter e
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Electron flow notation

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Electron current and conventional current are two types of notation we use to mention current flow in circuit. These two notations are opposite to each other. We need a notation to do some calculations like in Kirchhoff’s law. And we consider conventional current as the standard notation of current flow. But actually this notation is scientifically not correct but all the laws are followed with this notation. So before we get into these notations, we need to understand charges. Charges – Positive and Negative Charges First of all Franklin assumed an electric charge which moved in the opposite direction that it should actually be doing, so he called this electric charge “negative” which means deficiency of charges and so we can consider “positive” means surplus of electric charges. After some time, true direction of flow of electrons was discovered and it was noticed that this labels of positive and negative is incorrect scientifically. But by that time the notation of posi
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Types of current and their applications

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Electric current is the amount of electric charges that passes through a wire with respect to time. When battery is connected across a conductor, electrons move from negative terminal to positive terminal of battery. They move with very high velocity (more than the speed of light) and thus produce some amount of heat energy. Due to this, light bulbs glow. Electric current is of two types: Alternating current (AC) and direct current (DC). The difference is that direct current flows in one direction while alternating current changes its direction rapidly. Both AC and DC have their own specific uses but AC is more common type of current that we use today at home, offices, etc. Nikola Tesla and Thomas Edison invented AC and DC respectively. They battled over the standardization of the current notation. After all AC won the battle when it powered France Fair and finally it came into existence. Alternating current: An electric current is current that reverses its direction m
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