Question 1

Two factors that limit the current taken by a motor armature from a given line are the counter emf and the resistance.&#10;A)starting&#10;B)ohmic&#10;C)AC&#10;D)armature

Accepted Answer

The armature resistance limits the current in the motor armature along with the counter electromotive force (emf).

Question 2

The counter emf equals the applied voltage the armature (IR) drop.&#10;A)plus&#10;B)minus&#10;C)times&#10;D)divided by

Accepted Answer

The counter emf is always opposing the applied voltage, so it is "minus" the armature (IR) drop. Therefore, the correct choice is B. The counter emf is always opposite in polarity to the applied voltage. Therefore, it is subtracted from the applied voltage to determine the voltage drop across the armature (also known as the IR drop).

Question 3

The current taken by the armature will be abnormally high unless the DC supply is increased gradually.

Accepted Answer

This statement is true. If the DC supply is increased suddenly, the armature may not be able to handle the sudden surge of current, leading to abnormally high current and potential damage to the motor. Gradually increasing the supply allows the armature to adjust to the increasing load and prevents this issue. This is because sudden increase in DC supply can cause a surge in current which can damage the armature windings. Gradual increase in supply helps to reduce this surge and protect the armature.

Question 4

The total starting current is equal to the armature current plus the field current of 1 ampere.

Accepted Answer

This statement is correct. The total starting current of a DC motor is equal to the sum of the armature current and the field current, which is typically around 1 ampere. This is correct according to the basic principles of DC motors, where the starting current is usually the sum of the armature current and field current.

Question 5

The starting of fairly large DC motors requires that current be increased gradually and at the same time resistance must be inserted in series with the armature of the motor.

Accepted Answer

The answer of The starting of fairly large DC motors...

Question 6

The proper resistor can be selected by knowing the required resistance and the power value in .&#10;A)ohms&#10;B)watts&#10;C)amperes&#10;D)hertz

Accepted Answer

The required resistance (in ohms) and the power value (in watts) are the two most important factors when selecting a proper resistor. The amperes and hertz are not directly related to resistor selection. The power rating of a resistor is crucial in selecting the proper one, as it determines how much power the resistor can safely dissipate without overheating or burning out. Ohms and amperes are also important values to consider, but they are not the primary factors in selecting a resistor. Hertz, on the other hand, is a unit of frequency and is not relevant to resistor selection.

Question 7

The resistance in series with the armature reduces the starting armature current to approximately times the full-load current value.&#10;A)1.5&#10;B)3&#10;C)6&#10;D)12

Accepted Answer

The resistance in series with the armature reduces the starting armature current to approximately 1.5 times the full-load current value.

Question 8

Resistors may be rated in watts.

Accepted Answer

Resistors are rated in watts to indicate the amount of power that can safely be dissipated through them without damage. Resistors are rated in watts to indicate their power handling capacity.

Question 9

The counter emf developed by a motor is proportional to the speed of the motor unless the field is constant.

Accepted Answer

The counter electromotive force (emf) developed by a motor is proportional to the speed of the motor and the magnetic field strength. If the field is constant, the counter emf is directly proportional to the speed.

Question 10

Excessive torque and heat may cause the insulation to overheat on starting and the of the armature.&#10;A)reduction&#10;B)movement&#10;C)burning&#10;D)discoloration

Accepted Answer

Excessive torque and heat may cause the insulation to overheat on starting and the burning of the armature. Excessive torque and heat can cause the insulation on the armature to overheat and eventually burn.

Deck 44: Use of Reduced Voltage for Starting