This set of Automotive Engine Auxiliary Systems Multiple Choice Questions & Answers (MCQs) focuses on “Types of Ignition System”.
1. Which of the following is defined as the actual high voltage at which the spark occurs?
a) Cut-in voltage
b) Saturated voltage
c) Breakdown voltage
d) Cut-off voltage
Explanation: A battery of 12 volts is generally preferred. However, a very high voltage surge of about 25,000 volts in modern engines for ignition purposes. The actual high voltage at which the spark occurs is called the breakdown voltage.
2. Which of the following factors spark creating voltage does not depend on?
a) The gap and polarity
c) Plug insulation
d) Engine speed
Explanation: The voltage at which spark occurs is called breakdown voltage and it depends upon so many factors like the gap, polarity and condition of plug electrodes, condition of plug insulation, moisture on the distributor cap, and spark plugs.
3. What is the function of the ignition coil which is simply a transformer?
a) Step up the current
b) Step down the current
c) Step down the voltage
d) Step up the voltage
Explanation: The ignition coil is simply a transformer with certain characteristics making it suitable for its special use but impairing to some extent its efficiency as a transformer. It serves to set up the low battery voltage to high voltage.
4. What is the total resistance in ohms offered by primary winding in the ignition coil?
Explanation: The battery winding consists of 200-300 turns of thick wire of total resistance about 3 ohms while the secondary is made up of a large number of turns about 15,000-20,000 of fine wire.
5. Which of the following is used as a material for insulation in the ignition coil?
Explanation: The voltage difference between the adjacent turns is small, only think insulation is required and enameled wire is used. However, there is sufficient voltage drop between the layers and for this purpose, the paper is used for insulation.
6. What is the type of resistor that is used to avoid overheating and to decrease the amount of current in the primary circuit?
a) Ballast resistor
Explanation: When the engine is running at a slow speed, the contact breaker point is closed for a comparatively longer period. This causes overheating of the induction coil. To avoid this a ballast resistance is inserted in the primary circuit of the coil.
7. What is the gap in millimeters in the contact breaker?
Explanation: The contact breaker gap is between 0.35 to 0.45 millimeters. In case the gap is too small the points will not open for the period which is sufficient for the coil to function. This will cause the points to burn rapidly and the engine to misfire at all the speeds.
8. How can the center electrode make concerning earth to increase the plug life?
c) Short circuit
Explanation: The advantage of negative earth type is that comparatively less voltage is required for the electrons to jump from the central electrode which is hotter than the outer electrode. Further, the center electrode is made negative concerning the earth, thus the plug life is increased.
9. Which of the following is used to store the inertia of the current flowing during the contact period?
a) Contact breaker
d) Ballast resistor
Explanation: Condenser is a kind of plastic container in which the energy due to the inertia of the current flowing during the contact period is stored. The condenser absorbs excess energy during the break period.
10. Where is the condenser placed in the ignition circuit?
a) Contact breaker
b) Distributor housing
c) Ballast resistor
d) Spark plug
Explanation: The condenser is always mounted in the distributor housing. The condenser consists of metallic plates usually of tin foil or aluminum foil separated by thin sheets of insulating paper or mica.
11. Which among the following is not a requirement of a good contact breaker?
a) Must open and close at the correct time
b) Contacts must close without bounce
c) Minimum corrosion
d) Contacts should open with fling
Explanation: The essential requirements of a good contact breaker are the contact must open and close at the correct time, the contacts must close without bounce, the corrosion of the points should be minimum. Whereas the contacts must open without fling.
12. Which is the material used to make the rotor and a cap of the distributor?
Explanation: The distributor proper consist of a rotor and a cap, both of these are made of bakelite. Apart from the bakelite, the other material used is alkyl plastic phenol resin, fiberglass-reinforced polyester resin plastic.
13. How is the voltage of the used spark plug to fire when compared to a new spark plug?
a) High voltage
b) Less voltage
c) Has no effect
d) Depends on the current value
Explanation: Used spark plugs may require a fairly higher voltage to fire than the new plugs because of the increase in the gap and rounding off of the center electrode. In a given engine the highest ignition voltage is required during part throttle acceleration.
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