An ignition circuit is made up of two sub-circuits: the primary, which carries low voltage; and the secondary, which carries high voltage. The primary circuit is controlled by the ignition key. It releases 12 volts of electricity from the battery or alternator through the coil to a set of breaker points in the lower part of the distributor, or to the relay in electronic ignition applications. When the points or relay are closed, current flows through the chassis back to the battery, completing the circuit. When the points or relay are open, the flow stops, causing a high-voltage surge to pass from the coil through a rotor in the top of the distributor to the spark plugs. Once the car has started, the voltage regulator protects the battery from being overcharged by the alternator. part of the low -voltage current is absorbed by the condenser when the points are open.

Idler Gears

These are small gears which are not directly linked to anything. Idle gears are used to reduce or increase rotation speeds, and reverse directions of rotation. The center gear would be considered an idle gear, if three gears are connected in a string.

Indicator Needle

This is the pointer on your gauge that shows you the gauge's current reading. Its examples are those found in your speedometer, temperature gauge, tachometer and oil pressure gauge.

Intake Stroke

The first stroke is called the intake stroke. The piston moves down the cylinder, creating a partial vacuum in the cylinder. A mixture of air and fuel is then forced through the inlet valve into the cylinder by atmospheric pressure, now greater than the pressure in the cylinder. The exhaust valve stays closed during the stroke.