How does breaker point ignition work

The current flowing in the primary circuit would tend to arc across the breaker gap as it opens, and dissipate all the energy in the primary coil. The condenser absorbs the current and brings the flow to a quick stop.

When the current stops quickly, the magnetic field in set up by the primary coil collapses. The moving magnetic field induces a current in the secondary windings in the ignition coil. Since the secondary winding has a great many more windings than the primary, the induced voltage is very high, perhaps around 15, volts.

The secondary coil is connected to the spark plug. This very high voltage is sufficient to make an arc jump across the spark plug gap. The energy in the secondary winding dissipates as the spark plug fires, and the current stored in the condenser discharges back through the primary circuit. The process is ready to start again on the next ignition rotation of the engine. Lets reconvene in your inbox! I know you're busy. The distributor cap is made of nonconductive plastic, and the current is fed to its central electrode by the HT lead from the centre of the coil.

Inside the cap there are more electrodes often called segments to which the sparkplug leads are connected, one per cylinder. The rotor arm is fitted on top of the central shaft, and connects to the central electrode by means of a metal spring or spring-loaded brush in the top of the distributor cap. The current enters the cap through the central electrode, passes to the centre of the rotor arm through the brush, and is distributed to each plug as the rotor arm revolves. As the rotor arm approaches a segment, the contact-breaker points open and HT current passes through the rotor arm to the appropriate sparkplug lead.

The contact-breaker points are mounted inside the distributor. They act as a switch , in synchronisation with the engine, that cuts off and reconnects the 12 volt low-tension LT circuit to the coil. The points are opened by cams on the central shaft, and are closed again by a spring arm on the moving contact. With the points closed, LT current flows from the battery to the primary windings in the coil, and then to earth through the points.

When the points open, the magnetic field in the primary winding collapses and high-tension HT current is induced in the secondary windings. On a four-cylinder engine there are four cams.

With each full rotation of the shaft the points open four times. Six-cylinder engines have six cams and six electrodes in the cap. The ignition distributor does two jobs: First, its set of contact points act as a fast acting switch which produces a high voltage surge.

Second, it distributes the voltage surge in the correct firing order. The spark plug has two electrodes positioned to form a gap, over which the spark jumps to ignite the fuel-air mixture.

The system consists of two circuits; the primary and secondary. When the key is turned ON, which connects the battery to the circuit, the contact points close and current flows through the primary winding. This produces a magnetic field around the primary windings in the coil. As the cam rotates, it swings the arm on a pivot as the cam lobes push on the rubbing block. When the contact points open, current flow stops and the magnetic field collapses.

As it collapses, it cuts across the thousands of turns of wire in the coil secondary. This produces a voltage in each turn. These add together to produce the high voltage delivered through the secondary circuit to the spark plug.