Which of the following is used to check the gap between contact breaker points?
Measuring Contact Breaker Point Gap
The question asks about the correct tool used to measure the small gap between contact breaker points in an ignition system. This gap is crucial for the proper timing and functioning of the ignition system.
Understanding Contact Breaker Points and Their Gap
Contact breaker points were historically used in the ignition systems of older vehicles (before electronic ignition became common). They are essentially a mechanical switch that opens and closes to interrupt the primary circuit of the ignition coil. This interruption causes a high voltage to be induced in the secondary coil, which then fires the spark plug.
The gap between the contact breaker points when they are fully open is a critical setting. If the gap is too small or too large, it affects the dwell angle (the time the points are closed, allowing the coil to build up a magnetic field) and ignition timing, leading to poor engine performance, misfires, or difficulty starting.
Accurately measuring this small gap requires a specialized tool designed for checking clearances or spaces between components.
Identifying the Correct Tool: Feeler Gauge
A feeler gauge is the standard tool used to measure small gaps or clearances. It consists of a set of blades of different, precisely measured thicknesses. The blades are typically made of steel and are marked with their thickness.
To measure a gap using a feeler gauge, you select a blade (or combination of blades) that you believe matches the gap size. You then try to insert the blade into the gap. The correct blade should slide into the gap with a slight drag, indicating that its thickness is equal to the gap dimension. If the blade is too thin, it will slide in easily; if it is too thick, it won't fit.
The feeler gauge is ideal for checking the gap between contact breaker points because it is specifically designed for measuring such small, precise clearances where other tools like micrometers or vernier calipers are not practical or accurate due to the nature of the space being measured.
Analyzing Other Options
- Micrometer gauge: A micrometer is used for measuring the outside or inside dimensions or depth of objects with very high precision. While accurate, it is not designed for measuring the clearance between two surfaces like contact breaker points.
- Wire gauge: A wire gauge is used to measure the diameter of wire or the thickness of sheet metal. It is not suitable for measuring gaps or clearances.
- Vernier gauge: A vernier gauge (like vernier calipers) is used for precise measurement of length, diameter, or depth. Like a micrometer, it measures the dimensions of objects rather than the clearance between them in this context.
Therefore, the feeler gauge is the appropriate tool for checking the gap between contact breaker points.
The tool specifically designed for checking the gap between contact breaker points is the feeler gauge.
| Gauge Type | Primary Use | Suitable for Contact Breaker Gap? |
|---|---|---|
| Feeler Gauge | Measuring small clearances/gaps | Yes |
| Micrometer Gauge | Precise measurement of object dimensions (OD, ID, depth) | No |
| Wire Gauge | Measuring wire diameter or sheet thickness | No |
| Vernier Gauge | Precise measurement of object dimensions (length, diameter, depth) | No |
Revision Table: Ignition System Tools
| Tool | Application in Ignition System (Older Vehicles) | Purpose |
|---|---|---|
| Feeler Gauge | Checking contact breaker point gap | Ensuring correct dwell angle and timing. |
| Timing Light | Checking ignition timing | Verifying spark occurs at correct engine position. |
| Dwell Meter | Measuring dwell angle | Checking the time contact breaker points remain closed. |
Additional Information: Importance of Contact Breaker Gap
Setting the correct contact breaker point gap is a fundamental part of tuning an ignition system that uses points. The gap directly influences the dwell angle. The dwell angle is the number of crankshaft degrees that the points remain closed, allowing current to flow through the ignition coil's primary winding. A correct dwell angle ensures the coil has enough time to build a strong magnetic field, but not so long that the points overheat or coil saturation issues arise.
Adjusting the contact breaker point gap involves loosening the points assembly and moving one of the contact points closer to or further from the other, then re-tightening it once the desired gap (measured with a feeler gauge) is achieved. This adjustment also affects the ignition timing, which often needs to be checked and reset with a timing light after adjusting the point gap or replacing the points.
Modern vehicles use electronic ignition systems, which replace mechanical contact breaker points with electronic switches (like transistors) and sensors, eliminating the need for point gap adjustment and maintenance.
Important Questions from Measuring Tools
Which of the following is NOT a type of comparator?
Which gauge is most suitable to measure cylindrical ring gauge?
Which of the following is used to measure the ovality of a cylinder bore?
The least count of a Vernier height gauge in the metric system is ______.
The least count of a screw gauge is ______.
