單項(xiàng)選擇題In a fixed displacement axial piston hydraulic motor, the speed is varied by（）

A.regulating the ratio between torque and speed via the torque limiter at the motor
B.directing the motor output flow through a bypass line
C.maintaining a constant flow and pressure input
D.controlling the input flow rate


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1.單項(xiàng)選擇題In a shell-and-tube type hydraulic fluid cooler, the amount of heat transferred from the hydraulic fluid to the cooling water depends upon（）

A.the temperature of the hydraulic fluid
B.the flow rate of the hydraulic fluid
C.the temperature of the cooling water
D.all of the above

2.單項(xiàng)選擇題An orifice-check valve placed in a hydraulic system is used to（）

A.regulate the fluid flow in either direction
B.restrict movement of hydraulic fluid in one direction, but allow free movement in the other direction
C.allow free movement of hydraulic fluid in both directions
D.allow a restricted fluid flow in one direction only

3.單項(xiàng)選擇題Purging air from a hydraulic system is necessary when（）

A.adding small amounts of oil to the system
B.the system has been overheated
C.the system has been drained and then filled with new oil
D.the system has been idle for a long period of time

4.單項(xiàng)選擇題Leakage of hydraulic fluid from around the shaft of a hydraulic motor may be caused by（）

A.permanent loss of pump suction
B.worn shaft seals
C.high level in the oil sump
D.low motor RPM

5.單項(xiàng)選擇題Air trapped in the hydraulic fluid of a steering system would be indicated by（）

A.an improper rudder response
B.hammering noises in the equipment or transmission lines
C.popping or sputtering noises
D.all the above