Page 74 - Apprentice Manual_Neat

S1-Q32.) To proportionally change voltage levels, which type of transformer should be used?

a.) Isolation
Isolation is a 1:1 ratio. No change occurs.
b.) Current
Current transformers measure current and create a proportional voltage for instrumentation. Voltage
levels are not changed.
c.) *Potential
Correct. A potential transformer is a voltage to voltage transformer. It may be step up or step
down.
d.) Ground
There is no such device.

Section 2: Prime Movers

S2-Q33.) BMEP is:

a.) *A measure of engine efficiency.
Correct. Brake Mean Effective Pressure is the measure of efficiency that they have chosen to
express engine output relative to engine displacement.
b.) A measure of energy
Energy is expressed in Watts.
c.) The British Thermal Units (Btu’s) required to get electrical power from mechanical power
This is not at all related to BMEP.
d.) Number of cycles per second generated by an alternator based on RPM
Frequency is calculated by RPM and coils.

S2-Q34.) If 2 complete revolutions of the crankshaft are required to complete the power cycle of an engine,
what type engine is it?

a.) 2-Stroke
2-Stroke engines require only one complete revolution of the crankshaft. The journal pulls the piston
down in the first 180º and forces it back up on the second 180º.
b.) *4-Stroke
Correct. The first stroke pulls the cylinder down for intake (180º), then back up for combustion
(360º), this forces the piston back down and produces power (540º), and finally back up for
exhaust (720º). This is two complete revolutions.
c.) 6-Stroke
No such engine is discussed, if it even exists.
d.) Cannot be determined without knowing the number of cylinders.
Number of cylinders has nothing to do with the number of strokes.

S2-Q35.) The ratio of maximum cylinder volume to minimum cylinder volume is know as:

a.) Avagodro’s number
Avagodro’s number is a chemistry term for number of atoms in 1 mole (6.28x1023). Not related to
cylinder volume.
b.) Bernoulli’s Principle
Bernoulli’s Principle relates to pressure and pressure differential.
c.) *Compression Ratio
Correct. The minimum volume will determine how much the air-fuel mix will compress. The
maximum volume will determine the force produced by the explosive gasses.
d.) Engine displacement
This is cubic inches or cubic liters. It is not a ratio of minimum to maximum.

EGSA Apprentice Certification Program Study Guide - Page 66