Module 3 Set-3

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#1. . How can the direction of rotation of a DC electric motor be changed

a) reverse the electrical connections to either the field or armature windings

b) interchange the wires which connect the motor to the external power source

c) rotate the positive brush one commutator segment

#2. The term that describes the combined resistive forces in an AC circuit is

a) impedance

b) resistance

c) total resistance

#3. Ohm’s law states that:

a) e.m.f. = current divided by resistance

b) resistance = current divided by e.m.f

c) current = e.m.f. divided by resistance

#4. If a heavy mechanical load is removed from a series motor

a) the speed will decrease and the armature current will decrease

b) the speed will increase and the armature current will decrease

c) the speed will increase and the armature current will increase

#5. Which of the following is most likely to cause thermal runaway in a nickel-cadmium battery

a) excessive current draw from the battery

b) high current charging of the battery to more than 100 percent of its capacity

c) a high internal resistance condition

#6. The method of ascertaining the voltage of a standard aircraft lead-acid battery is by checking __________

a) the voltage on open circuit

b) the voltage with rated load switched ON

c) the voltage off load

#7. One purpose of a growler test is to determine the presence of:

a) a shorted armature

b) an out-of-round commutator

c) a broken field lead

#8. Static charges remaining in an aircraft are dissipated by

a) the use of a conducting type nose wheel

b) bonding the aircraft to a refuel tanker

c) earthing the aircraft as soon as possible

#9. Total resistance in parallel for R1 and R2 is

a) RT = (R1 x R2) ÷ (R1 + R2)

b) RT = 1/R1 + 1/R2

c) 1/RT = 1/R1 + 1/R2

#10. Through which material will magnetic lines of force pass the most readily?

a) aluminium

b) iron

c) copper

#11. A loss of electrical insulation results in ____________

a) a short circuit between the supply and earth

b) an open circuit between the supply and earth

c) an open circuit in the supply

#12. An accumulation of hydrogen on the plates of a battery is known as

a) hydration

b) polarization

c) ionization

#13. Electric motors are often classified according to the method of connecting the field coils and armature. Aircraft engine starter motors are generally of which type

a) compound

b) shunt (parallel)

c) series

#14. If the correct supply were connected to a DC shunt motor which had lost its residual magnetism it would

a) fail to run

b) run in the reverse direction

c) run normally

#15. Power is the rate of doing work. It is measured in

a) joules/second

b) watts/second

c) joules x seconds

#16. If the resistance of a resistor which is in series with two other resistors is doubled

a) the current in that resistance is doubled

b) the current in that resistance is halved

c) the volts drop across that resistor increases

#17. The only practical method of maintaining a constant voltage output from an aircraft generator under varying conditions of speed and load is to vary the

a) strength of the magnetic field

b) number of conductors in the armature

c) speed at which the armature rotates

#18. A DC circuit containing a total resistance of 100 ohms has a current flow of 250 mA. The power dissipated in the circuit is

a) 0.4 watts

b) 6.25 watts

c) 5 watts

#19. The quill drive on an aircraft generator ___________________

a) makes possible the use of roller

b) damps out any commutator ripple

c) damps out vibrations