Chapter 16
1 watt = __ joule
1
A voltage of 40,000 V is applied to a conducting sphere with a total charge of 0.001 C. How much electric potential energy is stored in this charged object? A) 40 J B) 40,000,000 J C) 400 J D) 40,000 J
A
A(n) ___ converts ___ into ___. A) generator, mechanical energy, electrical energy B) generator, AC, DC C) motor, electromagnetic induction, electrical energy D) generator, electrical energy, mechanical energy E) motor, DC, AC
A
Current is equal to: A) voltage divided by resistance B) resistance multiplied by voltage C) voltage multiplied by resistance D) resistance divided by voltage E) current divided by voltage
A
If the voltage is increased: A) the current will increase B) the current will decrease C) the resistance will increase D) the resistance will decrease E) the current and resistance will increase
A
Samara's computer uses energy at a rate of 75 W. If she uses the computer for a total of 90 min, how much energy has been transformed? A) 405,000 J B) 6750 J C) 947,000 J D) 270,000 J
A
The strength of an electromagnet can be: A) increased by adding a ferromagnetic core B) decreased by adding turns of wire to the coil C) decreased by adding more layers of wire to the coil D) increased by adding an aluminum core E) increased by reducing the current through the wire
A
The transfer of electrical energy through a conductor: A) happens at nearly the speed of light B) is slower than the movement of the electrons in the conductor C) happens when marbles enter the conductor D) happens when marbles exit the conductor E) happens slower than a leisurely walking pace
A
What does it mean to say that a circuit is 'closed'? A) There are no breaks in the circuit path B) The resistance is so great that current cannot return to the battery C) The circuit path is connected in reverse D) The battery is not producing voltage to pump current through the circuit E) There are multiple breaks in the circuit path
A
What is a magnetic force? A) A force felt due to a nearby magnet or electric current, which creates a magnetic field. B) A force felt due to a nearby magnet or electric current, which creates an electric field. C) Any force felt that isn't gravity. D) A force felt due to a nearby magnet.
A
When given the current and resistance, power can be calculated by: A) multiplying the current times the current times the resistance B) multiplying the current times the difference between the voltage going into and going out of the device C) multiplying the voltage times the voltage times the current D) multiplying the resistance times the resistance times the current E) multiplying the resistance times the difference between the voltage going into and going out of the device
A
When given the current and voltage, power can be calculated by: A) multiplying the current by the difference between the voltage going into and going out of the device B) multiplying the resistance by the resistance and the current C) multiplying the current by the resistance D) multiplying the voltage by the difference between the current going into and going out of the device E) multiplying the current by the current and the voltage
A
Which best describes electromagnetic induction? A) A voltage induced by a changing magnetic field B) Converting mechanical energy into electrical energy C) Converting AC to DC D) Converting electrical energy into mechanical energy E) None are correct
A
Which is true about current in a parallel circuit? A) It divides among the branches B) All are true C) It is independent of the voltage D) It is the same in each branch E) It is produced by resistance
A
Which is true about resistance in a series circuit? A) The individual resistances sum to the total resistance of the circuit B) Each resistor is independent of the others C) It supplies current to the circuit D) Each resistor creates a 'voltage boost'
A
Which of the following statements is true regarding resistors? A) In a resistor like a light bulb, electric energy is transformed into other forms of energy like light and thermal energy B) In a resistor like a light bulb, electrons gain electrical potential energy as they pass through C) In a resistor like a light bulb, the current going in to the resistor is smaller than the current on the other side of the resistor D) In a resistor like a light bulb, the current going into the resistor is greater than the current on the other side of the resistor
A
Which of the following statements is true? A) Motors and generators can be either AC or DC B) DC is more efficient than AC C) AC is less expensive than DC D) Motors only use AC while generators only use DC E) Most homes are wired in DC
A
Closed circuit
A circuit with current flowing through it
Open circuit
A circuit with no current
How does a motor work
A current is passed through a coil which forces it to spin
Circuit
A path that electrons flow through
Resistivity
A property of the material an object is made of
Which is more efficient AC or DC
AC
Which is more expensive AC or DC
AC
How does an MRI machine work
Align magnetic dipoles in body which are particles in your body that act like tiny magnets. The movement of these can created a picture inside the body
What is an alternating current
Alternates the direction it flows through a circuit
Current is: A) the random movement of electrons from atom to atom B) the flow of charged particles through a conducting medium C) faster than the speed of light D) the flow of a conductor through charged particles E) only present when there is no voltage
B
Electrical resistance is caused by: A) the binding of the free electrons to the atoms B) collisions of free electrons with the outer electrons of the atoms C) the atoms of the material vibrating in response to heat D) the length of the conducting object E) the collisions of free atoms with their outer electrons
B
Resistance is equal to: A) voltage divided by resistance B) voltage divided by current C) voltage multiplied by current D) current multiplied by voltage E) current divided by voltage
B
Resistivity is: A) equal to the resistance of the object B) a property of a material C) low in materials with very few free electrons D) affected by the dimensions of an object E) high in materials with lots of free electrons
B
To create a magnetic field, a charged particle must be: A) negatively charged B) moving C) traveling through a wire D) stationary E) positively charged
B
Which of the following does not produce a magnetic field? A) Electric currents B) Stationary charges C) Moving charges D) Magnetic materials like iron
B
Which of the following is NOT an application of magnetic forces? A) Microphones B) Steam trains C) Electricity generation in power D) plants E) MRI scanners
B
Pros of DC
Batteries only create DC and can only be charged with DC
A ferromagnetic core: A) does not increase the strength of an electromagnet but provides support to the wire wrapped around it B) decreases the strength of the electromagnet because it contains magnetic domains that become randomly configured under the influence of a magnetic field C) increases the strength of an electromagnet because it contains magnetic domains that align under the influence of a magnetic field D) increases the strength of an electromagnet because it is a permanent magnet E) is not used in most electromagnets
C
All magnetic fields are created by: A) permanent magnets B) electromagnets C) moving electric charges D) electrons moving around an atom E) electrical current in a wire
C
Fill in the blanks: When it comes to magnets, opposite poles ________and like poles _______. A) Attract; attract B) Repel; attract C) Attract; repel D) Repel; repel
C
If the temperature of a conductor increases, then: A) electrons moving through the conductor will lose less energy B) the resistance will decrease C) the resistance will increase D) electrons moving through the conductor will have fewer collisions E) the atoms in the conductor will stop moving
C
In a circuit, a voltage of 240 V is applied between the ends of a light bulb filament. How much energy does each electron in the filament gain? A) 6.7x10 -19 B) 3.8x10 -19 C) 3.8x10 -17 D) 1.6x10 -17
C
Voltage is equal to: A) resistance multiplied by voltage B) current multiplied by voltage C) current multiplied by resistance D) current divided by resistance E) resistance divided by current
C
What is the main difference between parallel and series circuits? A) In parallel circuits electrons flow counterclockwise, and flow clockwise in series circuits B) Electrons flow from the positive battery terminal to the negative one in parallel circuits, but from the negative terminal to the positive one in series circuits. C) Parallel circuits connect devices along branched pathways, while series circuits connect devices in a row D) None are correct E)Parallel circuits connect devices in a row, while series circuits connect devices along branched pathways
C
Which is true about current in a series circuit? A) A closed circuit has no current B) All are correct C) It is the same in every part of the circuit D) An open circuit has current E) One blown bulb will not a ect the others
C
Which is true about voltage in a series circuit? A) It is proportional to current B) The sum of each voltage drop is C) equal to the total supplied voltage D) All are correct E) There is a voltage drop at each resistor
C
Pros of AC
Can easily transform to other voltages so good for long distance power transmission
Resistance
Comes from the device itself and is an opposition to electron movement through the device
Series circuit
Connect devices in series
Parallel circuit
Connects devices along branched pathways
How does a school bell work
Contains a hammer which hits the bell. When it drops it connects to a circuit powering an electromagnet, which lifts the hammer back up again
Electrical motor
Converts electrical energy into mechanical energy
Generator
Converts mechanical energy into electrical energy
How are magnetic fields created
Created by moving particles
Alternating current: A) is not used in houses because it is dangerous B) is created by batteries C) is not good for long-distance power transmission D) changes direction several times per second E) cannot be created by generators
D
Direct current: A) is best for long-distance power transmission B) is becoming less and less important C) causes the lights to flicker in your house D) is the flow of electrons in one direction E) is easier to transform to other voltages than alternating current
D
Electrical resistance: A) is caused by free electrons in the material B) is a measure of a material's resistivity C) increases with increasing current D) is a measure of how much an object impedes an electric current E) is another name for resistivity
D
Electromagnetic induction was discovered by A) Thomas Edison B) Nikola Tesla C) Benjamin Franklin D) Alexander Graham Bell E) Michael Faraday
D
In a parallel circuit, the branches A) decrease the overall circuit resistance when added B) are connected in parallel C) have the same voltage D All are correct E) are independent of each other
D
Increasing the current through a wire: A) causes the magnetic domains to lose alignment B) does not a affect the magnetic field around the wire C) causes the magnetic field around the wire to decrease D) causes the magnetic field around the wire to increase E) does not a affect the strength of an electromagnet
D
Joe operates a 60 W light bulb for 20 min. During that time, how much electrical energy is transformed into other forms of energy in the bulb? A) 3600 J B) 1200 J C) 216,000 J D) 72,000 J
D
One watt is equal to: A) voltage divided by current B) resistance multiplied by voltage C) ten joules per second D) one second per joule E) one joule per second
D
The resistance of a wire increases if: A) the cross sectional area is increased B) the resistivity is decreased C) the diameter is increased D) the length is increased E) the length is decreased
D
The two types of current are: A) indirect and alternating B) direct and attenuating C) directive and alternative D) direct and alternating E) none of the answers are correct
D
The unit of electrical power is the: A) newton meter B) walt C) horsepower D) watt E) joule
D
What is the difference between series and parallel circuits? A) Parallel circuits connect devices one after another B) Parallel circuits are open C) Series circuits connect devices along branched pathways D) Series circuits connect devices one after another E) Series circuits are open
D
Which best defines a circuit? A) None are correct B) A path for voltage flow C) A series of resistors D) A path for electron flow E) A series of check points
D
Which of the following is NOT a storage medium that uses magnets? A) Hard drives B) VHS tapes C) Cassettes D) CDs
D
Increasing diameter ___ resistances. Why?
Decreases. The electrons have more cross sectional room to move through
What is a direct current
Does not change direction as it flows through a circuit
If the resistance is increased: A) the voltage will decrease B) the voltage will increase C) the current will not change D) the current will increase E) the current will decrease
E
Power is a measure of how much: A) resistance a device has over time B) energy is used by a resistance C) current passes through a device over time D) voltage passes through a device over time E) energy is used over a period of time
E
Which best describes Ohm's Law? A) The current is proportional to both the voltage and the resistance B) The current is inversely proportional to both the voltage and the resistance C) The current is inversely proportional to the voltage and proportional to the resistance D) The current is supplied by a battery and encounters resistance at each device E) The current is proportional to the voltage and inversely proportional to the resistance
E
Which of the following statements is NOT true? A) Direct current does not change direction as it flows B) Alternating current changes direction as it flows C) Motors produce mechanical energy from electrical energy D) Generators produce electrical energy from mechanical energy E) A generator can be turned into a motor by reversing the movement of the internal components
E
Equation for finding the total of energy transformed
E = P x t
What do generators produce and how
Electricity by rotating a coil in a stationary magnetic field
The amount of electrical potential energy acquired by a charge object is ____ to the voltage applied multiplied by the charge of the object
Equal
Magnetic Force
Force felt from a nearby magnet, or electric current
Materials with more tightly bound electrons have a _____ resistivity? Why is that so?
Higher. Have fewer free electrons, more opportunity to collide into each other
Increasing length ____ resistance. Why?
Increases. There are more collisions happening
Temperature factor
Increasing the temperature of a conducting object will cause resistance to increase
Electromagnets
Magnet that uses an electric current to generate its magnetic field
What are Ferromagnetic materials
Materials that enhance a magnetic field
Power
Measure of how much energy is used over a period of time
When electrons move through an area where there is a lot of resistance, some of their energy is transformed into what?
Other forms of energy like thermal energy and light
Branches pathways
Parallel circuits have devices that are connected in a parallel fashion. Each circuit is independent
Ohm's Law
States that the current is directly proportional to the voltage across the circuit and inversely proportional to the resistance
Electrical resistance
The amount an object impedes an electrical current
Dimensional factor
The length and diameter of a wire can affected its resistance
Ampere
The unit of current
Watts
Unit for electrical power
Electromagnetic induction
When a voltage is induced by a changing magnetic field
As branches in a circuit increase the overall resistance is _____
decreased
Unit of Ohms
how electrical resistance is measured
Equation for Ohm's law
i = v/r
Calculating electrical power used by a device
multiplying the current by the different between the voltage going into and out of the device AND Multiplying current times the resistance
More condensed the electromagnet is the ___ the magnetic field
stronger
More current equals ______ magnetic field
stronger
