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 ...

WORK : Work is said to be done by force F when the point of its application moves Mathematically, through a distance S. Work = force x distance            = F x S an acceleration of one The unit force in the mks system is newton (N). defined as the force acting on one kilogram mass of a body for one second which gives metre per second. If in the above equation, . force = 1 N and distance = 1 m, then Work done = 1 N-m or joule (J) In the mks system of units, work done is given in joules. It is defined as the work done by a force of one newton when the point of its application moves through a distance of one metre in the direction of the force. Therefore 1 J = 1 N-m POWER :  Power may be defined as the rate of doing work. Mathematically, work done Power time Note : Work done or energy expanded = power x time. If in time t sec, a quantity of electricity Q is transferred between the ends of a conductor when a potential difference is V, then...

AMMETER An ammeter is required to measure the current. Therefore, it must be connected in series to the load of which the current is to be measured. As it is connected in series, it must have low resistance, otherwise the resistance of the instrument will appreciably change the current through the load. For connecting it in series with the load, open the circuit at one place and connect the meter in the circuit as shown in Figure. Note : An ammeter should never be connected in parallel with the load otherwise it can get damaged. VOLTMETER A voltmeter is used to measure the potential difference. Therefore it must be connected in parallel to the circuit of which the potential difference is to be measured. A voltmeter must have high resistance otherwise it will take heavy current. When a voltmeter is connected in series, it measures the voltage drop across its own terminals. For connecting the voltmeter in parallel to the circuit, the meter should be connected across the load ...

CONNECTING ELECTRICAL CIRCUITS When electrical components are connected, they may be placed either end on end (called series circuit) or side by side (called parallel circuit). SERIES CIRCUITS : When circuit components are connected with only one conducting path they are said to be connected in series. The same current is in all components. When batteries are connected in series, (the voltage obtained in the circuit will be a total of the voltage in the batteries. This principle is used in car batteries and many radio batteries, where voltages larger than 1.5 or 2 volts are required. In these cases the cells are joined together in series. If resistors are connected in series the resistance in the circuit will be equal to the sum of all resistors. i.e.  R = R1 + R2 + R3 + R4 PARALLEL CIRCUITS : When circuit components are connected with several conducting paths between the sources of e.m.f. they are said to be connected in parallel. When batteries are connected in parall...

ELECTRICAL CURRENT The movements of electrons along the conductor in a particular direction produce an electric current. The more electrons which move the greater the current. AMPERE : The amount of electron flow is the current and the current is measured in amperes. One ampere of current is said to flow when 6.28 x 10^18 electrons pass a given point in the conductor during a period of one second. The electric current or amperes (abbreviated amps) is measured by an ammeter.   DIRECT AND ALTERNATING CURRENT :  If the electrons flow continuously in one direction along the conductor, the current is said to be direct current (abbreviated d.c.). This is the type of current produced by a battery or a d.c. generator. If the electrons flow in one direction and then flow back again and continue this back and forth motion, the current is said to be alternating current (abbreviated a.c.). This is the type of current produced by an alternator or a.c. generator and is the type of electric...

MAGNETO COIL IGNITION SYSTEM The above figure shows the diagram of a Magneto coil ignition system. It contains two circuits like primary and secondary circuits. The primary circuit have a rotating magnet, Ignition switch, primary coil, CB point, and condenser. The secondary circuit having secondary coil, HT cable, distributor, rotor and spark plug. The magneto is a self-contained generator of high voltage that provides ignition to an engine through spark plugs. The moment the contact points open, a rapid magnetic flow generates a high voltage in the secondary coil, which ignites the spark plug, thus firing the engine.