AUTOTECH Kerala

BALLAST RESISTOR A ballast resistor is defined as a resistor inserted into a circuit to minimize current. Ballast resistors also help to avoid over-current faults in a circuit. An “electric ballast” is a more general term used to refer to an electrical device used to maintain a circuit’s stability by limiting the value of current and voltage. Electric ballasts can be resistors, capacitors, inductors, or a combination of these. Ballast resistors are able to change resistance with the current. If the current flowing through the resistor increases above the threshold value, the resistance increases. The resistance can then correspondingly decrease as the current decreases. In this way, the ballast resistor tries to maintain a constant current flowing through a circuit. The ballast resistor is different from the load resistor. As it acts like a variable load connected with the system. But in the case of load resistor, resistance remains constant with different values of current

FUSE If a circuit is closed but no resistor is in the circuit, a heavy or high current will flow and produce large amounts of heat in the wire and draw large quantities of power from the battery. The result is that the wire becomes very hot and in many cases burns. This is called a short circuit and is the cause of many fires. It may result in an electrical appliance becoming inoperative. To prevent this happening, each normal circuit is protected by a fuse which is device that holds a piece of thin wire and is placed in the circuit. If the heat in the wire should rise above an acceptable level, the wire in the fuse will heat and melt and open the circuit. No damage will be done to any device or wire and when the cause of the heating is fixed and the fuse replaced, the circuit is ready for use again. Fuse wires are bare wires made of easily melting materials having high specific resistance. Usually standard alloy (63% tin and 37% lead) fuse wires are used for small currents, say up to