ITEC 220 Test #2 Flashcards
Series circuit
Circuit in which current flows in one direction
Parallel circuit
Circuit in which current flows in one direction then alternates back and forth
Combination circuit
A circuit with both series and parallel sections
Series-parallel/complex circuit
Circuits with any combination of series and parallel sections
How many paths are in a series circuit
1 path
What is the disadvantage of connecting a large number of bulbs in series
A voltage drop
Are lights in our homes connected in series
No in parallel
How many paths are there in a parallel circuit
2 or more paths
What is the smallest number of paths a parallel circuit can have
2 paths
D’Arsonval meter movement
A meter movement that uses stationary magnet structure and a moving coil
Moving-coil meter
A meter movement that uses stationary magnet structure and a moving coil
Rectifier
A device that allows current to go one direction easily, but not the other direction
Full-scale value
The current that represents the maximum deflection of the pointer on the scale
Current sensitivity
The method of stating the resistance need to limit current to the full-scale value
Ohms per volt
The unit stating sensitivity of a meter movement
Shunt resistor
A resistor in parallel to the meter movement that measures the current greater than the full-scale value
Multiplier resistor
A resistor in series to the meter movement that measures the voltage greater that the full-scale value
Kirchhoff’s Voltage Law
In a circuit, the algebraic sum of the voltage drop is equal to the algebraic sum of the voltage rises across the source
Kirchhoff’s current law
The sum of the currents entering the junction are equal to the sum of the currents leaving the junction
What is the maximum voltage that can be measured when using 100 volt setting
100 V
When using the 1,000 volt range, by what number must the scale reading be multiplied
100
Axial resistor
A cylindrical shaped resistor whose leads come out of its axis
Radial resistor
A cylindrical shaped resistor whose leads come out at the sides or at the radius of the cylinder
What is the purpose of the function selector switch on a multimeter
To select different voltages and currents
An ohmmeter measures resistance through a conductor and resistor through a
Series circuit
What would be the resistance of a section of insulating material
Infinite
What is indicated by the first and second color bands on a resistor
The first and second digits of the resistors value
What is indicated by the third and fourth color bands on a resistor
The third is the multiplier and the fourth is the resistors tolerance
Gold fourth band
Plus/minus 5%
Silver fourth band
Plus/minus 10%
No fourth band
Plus/minus 20%
Variable resistor
A resistor whose resistance can be changed without disconnecting the circuit
Rheostat
A variable resistor, which has two terminals, and is used to control the current in a circuit
Potentiometer
A variable resistor, which has three terminals, and is used as a adjustable voltage divider
What is rheostat used for
To control the current in a circuit
What is a potentiometer used for
as a adjustable voltage divider
What is the physical difference between a rheostat and a potentiometer
A rheostat has two terminals and a potentiometer has three terminals
To control the current through a lamp, is the rheostat connected in parallel or in series
Connected in series
Define Kinetic energy
Energy associated with motion
Define Power
The rate of expending energy (doing work)
Basic unit of power
Watt
Define watt
One watt is the amount of work done in one second by one volt in moving one coulomb of charge
One Joule of energy is referred to as
A watt-second
1 watt hour equals
3,600 joules
Define horsepower
The mechanical unit of power
The cold resistance of a light bulb is less than its hot resistance. Would it be more likely to burn out when first turned on or later
First turned on
Residual magnetism
Magnetism that a material retains after the magnetizing force has been removed
Poles
The ends of a magnet (labeled north and south)
Magnetic field
Any region in which a magnetic force is exerted
Ferromagnetic
Any material that exhibits strong magnetic properties
Magnetism by induction
The magnetism a object acquires by being in a magnetic field
Permanent/hard magnets
Material that retains much of the magnetism after the magnetic force has been removed
temporary/soft magnets
Material that loses its magnetism after the magnetic force has been removed
Permeability
Measure of the ability of a substance to conduct magnetic flux
Reluctance
Ability of a material to oppose passage of magnetic lines of force through them
Magnetic dipoles
Smallest particles of a substance that has magnetic properties
1 kilowatt is…
1,000 watts
To convert watts to kilowatts
Move the decimal three places to the left
1 kilowatt-hour is…..
1,000 watt-hours
To convert watt-hours to kilowatt-hours
Move the decimal three places to the left
A watt is equivalent to
1 joule per second
A unit of power (horsepower) is equivalent to
550 foot-pounds of work done in one second
One watt is the same as an electromotive force of….
One volt multiplied by a current of one ampere
Unlike poles of magnets attract or do not attract
Attract
Is the pointer on the compass needle a north magnetic pole or a south magnetic pole
South magnetic pole
Standing halfway between the equator and the south geographic pole of the earth, in which direction would the compass point
North
All materials are affected when placed close to magnets
False
The north pole of a magnet induces what pole into the end of a material attached to it
South
How would you demagnetize a screw driver
Heat it up, hit it with a hammer, or put it in another magnetic field with AC current
Two ferromagnetic substances
Nickle and Cobalt
Two non-ferromagnetic substances
Chrome and Zinc
Electromagnetism
The phenomenon whereby an electrical current produces magnetic effects
Coil / Solenoid
An electrical device that consists of turning insulated wires that produce a magnetic field
Is a magnetic field around a wire temporary of permanent
Temporary
The intensity of a magnetic field is (directly, inversely) proportional to the distance from a conductor
Inversely
Winding more turns on a coil will (increase, decrease) the magnetic field
Increase
Electromagnet
Is a device that behaves as a magnet when external power is applied to it.
What is an example of a electromagnet
A solenoid with a soft iron-core
Relay
A device that is operated by changing conditions of one electric circuit to affect the operation of devices in the same circuit or different ones
Why is an electromagnet preferred over a permanent magnet
It can be turned off and used in mechanical apps
Electromagnets are why type of magnets
Temporary magnets
What must you have to operate an electromagnet
External power and a solenoid with soft iron-core
What is another name for a electromechanical switch
Relay
Induced voltage / Induced current
Voltage produced in a conductor by its movement in a magnetic field
In what direction must a conductor be moved to induce maximum current into the conductor
Perpendicular
What can be done to a conductor to increase the current induced into it when it is moved through a magnetic field
Move the conductor at right angles
What effect does the use of a steel core have with respect to induced current
The steel core only picks up part of the magnetic field
When current in a coil is neither increasing or decreasing, what is the state of the field surrounding the coil
Remains in a steady state
Why does a current-carrying wire move when in a magnetic field
Because there is a magnetic field around the wire
Name some uses of current-carrying conductors moving in a magnetic field
Motors, generators, and transformers
Left hand rule
Determines the direction of the induced current in the conductor
What do the fingers represent in the left hand rule
Thumb - motion of conductor, Index finger - location of magnetic field, and middle finger - direction of the current flow
Right hand rule
Determines the motion of the current-carrying conductor in a magnetic field
What do the fingers represent in the right hand rule
Thumb - motion of the conductor, Index finger - the direction of the magnetic field, and middle finger - the direction of current flow
How can an electric bell be made into a buzzer
Remove the hammer and bell
Uses of a buzzer
Attention-getting device and doorbell replacement
What is meant by normally opend contacts on a relay
Normally open contacts are when the relay coils are deenergized. They close when the relay coil is energized
What is the purpose of a circuit breaker
It protects a circuit from an excessive-current condition
