Font size
WorksheetsEE 311 Quiz #1
Total questions: 70
Worksheet time: 1hrs 16mins
The machines which are operated in relation with electrical energy are called (a)
What are the two main types of electrical machines?
Static Electrical Machines
Rotating Electrical Machines
Simple Electrical Machines
Multiple Electrical Machines
A stationary electrical machine is kind of machine which has moving parts & they remain stationary throughout its operation.
True
False
Which of the following is a type of stationary electrical machine?
Motor
Generator
Transformer
All of the above
What is a type of machine that consists of moving parts as well as stationary parts?
(a)
What are the two types of dynamic/rotating electrical machines?
Electrical Motor
Electrical Generator
Step-up Transformer
Step-down Transformer
What is the electrical machine that the input and output are electrical power?
Motor
Generator
Transformer
Circuit Breaker
What is the electrical machine that the input is mechanical power and the output is electrical power
Circuit Breaker
Generator
Motor
Transformer
What is the electrical machine that the input is electrical power and output is mechanical power?
Motor
Generator
Transformer
Vacuum
Transformers only works on AC system.
True
False
Transformer works on the principle mutual resistance.
True
False
What are two types of transformers depending on the voltage level?
step up transformer
step down transformer
auto transformer
power transformer
What are two types of transformers depending on the design criteria?
step down transformer
power transformer
two winding tranformer
auto transformer
What are two types of transformers depending on the insulation system?
single phase transformer
three phase transformer
dry type transformer
oil immersed transformer
Electrical motors have a moving part called rotor & a stationary part called stator.
True
False
What are the three main types of DC generators based on their methods of excitation?
Permanent Magnet DC Generators
Separately Excited DC Generators
Self Excited DC Generators
Synchronous generators
Induction generators
What are the three types of self-excited DC generators?
Series Wound Generators
Shunt Wound Generators
Compound Wound Generators
Induction generators
Synchronous generators
What are the two types of AC generators
Series Wound Generators
Shunt Wound Generators
Compound Wound Generators
Induction generators
Synchronous generators
What are the two types of AC generators?
the stationary field, rotating armature
the rotating field, stationary armature
the rotating field, rotating armature
the stationary field, stationary armature
What are the two types of Three-phase AC generators?
series connection
parallel connection
wye-connection
delta-connection
Almost all practical motors and generators convert energy from one form to another through the action of a magnetic field.
True
False
Almost all electric machines rotate about an axis, called the shaft of the machines.
True
False
(a) is the angle at which the rotating body is oriented, measured from some arbitrary reference point. Its measurement units are in radians (rad) or in degrees. Usual symbols is theta.
For a rotating body, (a) defined as the velocity at which the measured point is moving. Usually measured in rad/s or rpm.
(a) is defined as the rate of change in angular velocity with respect to time. Usually measured in rad/s2.
What is known as a rotational force applied to a rotating body giving angular acceleration, a.k.a. ‘twisting force?
Torque
Work
Angular Acceleration
Power
What is defined as rate of doing work and is equivalent to torque times angular velocity when applied to the shaft of a generator or motor?
Power
Work
Momentum
Inertia
What law is stated in the picture?
(a)
Magnetic fields are the fundamental mechanism by which energy is converted from one form to
another in motors, generators and transformers.
True
False
What is the basic law governing the production of a magnetic field by a current?
(a)
What is the unit of measure of magnetic flux density?
Ampere
Tesla
Henry
Farad
The value of relative permeability is dependent upon the amount of material used.
True
False
Relative permeability is a convenient way to compare the magnetizability of materials.
True
False
In magnetic circuits, what does mmf means?
(a)
In an electric circuit R means resistance, however in magnetic circuit what does R means?
Reluctance
Magnetic Flux
Electromotive force
Permeance
In an electric circuit "right hand rule" is use to determine current flow, however in magnetic circuit what "right hand rule" determines?
Reluctance
Magnetic Flux
Electromotive force
Permeance
What is the inverse of reluctance and it represents the
degree at which the material permits the flow of magnetic flux?
Flux Density
Magnetic Flux
Electromotive force
Permeance
The magnetic circuit assumes that all flux are confined within the core, but in reality a small fraction of the flux escapes from the core into the surrounding low-permeability air, and this flux
is called (a)
What do you call the process of changing the form of energy such as convert mechanical energy into electrical energy or convert electrical energy into mechanical motion?
(a)
In energy conversion, the electrical system and the mechanical system are joined together by a coupling field which could be electrical or magnetic.
True
False
In motors, an electric current interacts with a magnetic field to cause an electromagnetic torque, which drives some load.
True
False
In generators, an electric current is applied to turn
conductors through a magnetic field and generate mechanical torque.
True
False
Which of the following is part of the five electromagnetic principles?
Ohm's Law
Ohm's Law for magnetic circuit
Ampere's Law
Newton's Law
Lenz's Law
Which of the following is not part of the five electromagnetic principles?
motor action
generator action
transformer action
coupling action
The determines the direction of the magnetic flux produced by the current is flowing in the coils?
right hand rule only
left hand rule only
both left hand rule and right hand rule
neither left hand rule nor right hand rule
In what rule does the outwardly extending thumb, then, points in the direction of the electromagnetic force?
right hand rule only
left hand rule only
both left hand rule and right hand rule
neither left hand rule nor right hand rule
In a simple linear motor, a conductor (called the ________) is free to move along a set of rails.
armature
current
magnetic field
magnetic flux
In a linear generator, current is generated in the coils by either rotating the coils through a magnetic field or
by rotating magnetic poles past stationary windings.
True
False
In simple ac machine, what do you call the assembly that rotates and delivers power?
rotor
stator
brushes
slip rings
In simple ac machine, what is use to to connect the coil to a source or load, and is placed around but insulated from, the shaft of the rotor?
rotor
stator
brushes
slip rings
What are the conducting blocks of carbon or carbon and copper, that are placed against the slip rings to make the connection to the outside of the machine?
rotor
stator
brushes
armature
What operation does the picture depicts?
AC Motor Operation
DC Motor Operation
AC Generator Operation
DC Generator Operation
What operation does the picture depicts?
AC Motor Operation
DC Motor Operation
AC Generator Operation
DC Generator Operation
In a three phase stator winding, The flux distribution due to the coil “b” is _________ coil “a” and the flux
due to the coil “c” is ______ coil “b”.
120 degrees behind
12 degrees behind
1200 degrees behind
1.20 degrees behind
In a simple DC Machine, instead of a pair of slip rings to connect to the ends of the coil, there is a single split ring called ________.
commutator
armature
brushes
split ring
In a simple DC Machine, a split ring is called a ________ and has the function of converting between AC in the armature and DC at the machine terminals.
commutator
armature
brushes
communicator
What operation does the picture depicts?
AC Motor Operation
DC Motor Operation
AC Generator Operation
DC Generator Operation
What operation does the picture depicts?
AC Motor Operation
DC Motor Operation
AC Generator Operation
DC Generator Operation
What is defined as is the power out divided by the power in?
(a)
The losses in the machine are converted to heat, which raises the operating temperature of the machine. The machine must be designed to tolerate the heat created by its losses.
True
False
The electric machines are rated in terms of power in.
True
False
What is the category of losses that includes friction and windage losses?
Copper Losses
Mechanical Losses
Core Losses
Stray Losses
What is frequently referred to as resistive losses in the winding of a machine?
Copper Losses
Mechanical Losses
Core Losses
Stray Losses
What losses include the hysteresis and eddy current losses in the magnetic core of the machine?
Copper Losses
Mechanical Losses
Core Losses
Stray Losses
What losses include any other losses and by convention, and is usually assume to be 1% of the output?
Copper Losses
Mechanical Losses
Core Losses
Stray Losses
The lifetime of the insulation is significantly reduced as the
temperature of operation increases.
True
False
Insulation deteriorates naturally with time due to mechanical failure and other physical reactions.
True
False
Using the efficiency formula:
A 0.75 kW, 230 V, single-phase motor has an input power 1 kW at full load.
Determine the percentage efficiency of the motor at this load.
75%
100%
133.33%
50%
Using the efficiency formula:
A motor running at 1425 rpm produces a torque of 30 Nm. At this torque the input power is 5.3 kW and the output is 4.47 kW, determine the percentage efficiency at this load.
84.3
92.7%
76.9%
61.5%
Using the efficiency formula:
If the motor is 86% efficient and input power is 8.68 kW, what is the output power?
7.46 kW
10.10 kW
7.46 HP
10.10 HP
