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Electric Circuit

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Rural Technology

Basically, an electric circuit consists of a power source, a safety device, controlling device and a device & wires to connect each other.

Simple Circuit

In this figure circuit consisting of only one lamp having resistance, safety device like fuse, controlling device like one way switch, & the voltage source and the connecting wires, it is called simple circuit. In this circuit D.C. generator, battery, or mains are sources and fuse is a safety device which is used to protect generator from heavy current.

Switch is used as controlling device to break the path of current i.e. to make on/ off lamp. A Lamp is a device which converts electrical energy into light energy as a device. We can use fan, tubelight, motors etc. In this circuit, when supply voltage is applied to the electrical device conventional current flows from positive terminal (+) of generator through the fuse element. Thereafter, it reaches one terminal of the switch, if switch is on it goes to second terminal of switch, next it goes to one terminal of lamp, current travels through the filament of lamp then it returns to negative terminal of generator through negative wire. This is complete path of electrical current.

Closed Circuit

In close circuit, when supply voltage is applied to the electrical device, conventional current start to flows from positive terminal (+) of generator through positive wire. It reaches one terminal of fuse & come out from another terminal of switch through the fuse element. Next it reaches one terminal of the switch, if switch is on it goes to second terminal of switch, next it goes to one terminal of lamp, current travels through one filament of lamp then it returns to negative terminal of generator through negative wire. This is complete path of electrical current. Resistance of close circuit is always medium & some power is wasted in this circuit.

Open Circuit

You already know that for current to flow through a circuit, a closed path must be provided between positive (+) & negative (-) terminals of the voltage source any, break in the closed path open the circuit & stops the flow of current. Any break in the circuit is known as open circuit. Open switch, a wall socket, broken wire, fused lamps, switch off are examples of open circuit. In an open circuit, there is an infinitely high resistance in the circuit; there is no voltage drop across the load. There is also no power used by the load & so the total power consumed in a circuit is zero.

Short circuit

You have seen how an open circuit prevents current flow by breaking the closed path between terminals of the voltage source. A short circuit produces just the opposite effects. A short circuit occurs whenever, the resistance of a circuit or part of circuit drops from its normal value to essentially zero resistance. This happens if two terminals of a lamp in circuits are directly connected, the voltage source leads contact each other or two current carrying uninsulated wires touches or the circuit is improperly wired these types of shorts are called short circuit. The resistance of the circuit becomes so very low that a very high current flows through the circuit. It causes to damages wiring, equipment or source. Circuits are usually protected against excessive current flow, by the use of fuses.

Rural Technology