ELE 74 QUIZ 12 CONTACTORS AND MAGNETIC MOTOR STARTERS QUESTIONS WITH DETAILED VERIFIED ANSWERS.pdf

ELE 74 QUIZ 12 CONTACTORS AND MAGNETIC
MOTOR STARTERS QUESTIONS WITH DETAILED
VERIFIED AND 100% ACCURATE ANSWERS



ELE 74 QUIZ 12: CONTACTORS AND MAGNETIC MOTOR STARTERS
Practice Examination – 140 Questions with Verified Answers


SECTION 1: CONTACTOR AND STARTER FUNDAMENTALS
Question 1
A magnetic motor starter is best described as:
A. A device that only provides overload protection
B. An electrically operated switch (contactor) that includes motor overload
protection
C. A manual switch for motor control
D. A variable frequency drive
Answer: B
Explanation: A magnetic motor starter is an electrically operated switch
(contactor) that includes motor overload protection. This distinguishes it from a
simple contactor, which lacks overload protection .


Question 2
Which of the following is NOT a component of a magnetic motor starter?

,A. Coil
B. Overload relay
C. Auxiliary contacts
D. Variable frequency drive
Answer: D
Explanation: A magnetic motor starter consists of a contactor (including a coil and
auxiliary contacts) and an overload relay. A variable frequency drive is a separate
device for speed control .


Question 3
The primary purpose of a magnetic motor starter in an industrial circuit is to:
A. Provide speed control
B. Safely start and stop a motor using electromagnetic switching
C. Convert AC power to DC
D. Reduce line voltage continuously
Answer: B
Explanation: A magnetic motor starter uses contactors and overload protection to
safely control motor operation remotely and protect the motor from damage .


Question 4
Which contact on a starter is typically used to seal in the control circuit?
A. Normally closed overload contact
B. Power contact
C. Normally open auxiliary contact
D. Control transformer primary
Answer: C

,Explanation: A normally open auxiliary contact closes when the starter is
energized, maintaining coil power after the start button is released. This is called
the seal-in or holding contact .


Question 5
What happens when an overload relay trips?
A. The control circuit voltage increases
B. The motor reverses direction
C. The control circuit opens and stops the motor
D. The motor runs at reduced speed
Answer: C
Explanation: An overload relay opens a normally closed contact in the control
circuit to de-energize the starter coil, stopping the motor .


Question 6
Which device provides short-circuit protection in a motor control circuit?
A. Overload relay
B. Auxiliary contact
C. Fuse or circuit breaker
D. Control transformer
Answer: C
Explanation: Fuses and circuit breakers interrupt excessive current caused by
short circuits, protecting conductors and equipment .


Question 7
What is the primary function of an auxiliary contact on a motor starter?

, A. Carry motor current
B. Provide control circuit functions such as sealing and interlocking
C. Protect against lightning
D. Increase motor horsepower
Answer: B
Explanation: Auxiliary contacts handle low-current control signals rather than
motor power. They are commonly used for seal-in circuits, electrical interlocks,
and status indication .


Question 8
In a standard three-wire motor control circuit, what is the purpose of the seal-in
contact?
A. Protect against overloads
B. Maintain the contactor coil after the start button is released
C. Increase motor torque
D. Reduce voltage
Answer: B
Explanation: The seal-in (holding) contact bypasses the momentary start
pushbutton after the contactor energizes, allowing the motor to continue running
until the stop button or another control device interrupts the circuit .


Question 9
Which pushbutton is normally closed in a standard motor control circuit?
A. Start button
B. Jog button
C. Stop button
D. Reset button
Answer: C