PHYS Chapter 23
When the filament breaks in one lamp in a series circuit, other lamps in the circuit normally _________. continue glowing, but dimmer continue glowing, but slightly brighter absorb energy from the damaged lamp go out
continue glowing, but dimmer
Of what physical quantity is Hertz a unit of? time taken by electrons as they travel down the wire number of times per second that the electrons move back and forth in the wire speed at which the electrons travel down the wire
number of times per second that the electrons move back and forth in the wire.
A flow of electric charge in a wire normally requires a _________. potential difference across the ends of the wire sustained energy difference across the ends of the wire pump voltage source
potential difference across the ends of the wire
When the parallel combination of 8.0-Ω and 4.0-Ω resistors is impressed with 20 volts, how much current is in it?
1/Rtotal=1/R1+1/R2
What is the equivalent resistance of a pair of 8.0-Ω and 4.0-Ω resistors when connected in parallel?
1/Rtotal=1/R1+1/R2 1/Rtotal=1/8.0+1/4.0= 2.67
An electric current of 5 amperes in a wire carries _________. 5 joules per ohm 5 volts per coulomb 5 coulombs per joule 5 coulombs per second
5 coulombs per second
Does electric charge flow across a circuit or through a circuit? Does voltage flow across a circuit or is it impressed across a circuit? Charge flows across and voltage is impressed across a circuit. Charge flows through and voltage is impressed across a circuit. Charge and voltage both flow across a circuit. Charge flows through and voltage flows across a circuit.
Charge flows through and voltage is impressed across a circuit.
What is the relationship between current, resistance, and voltage difference? Current = Resistance / Voltage Difference Current = Voltage Difference x Resistance Current = Voltage Difference / Resistance
Current = Voltage Difference / Resistance I=RV
Why are electrons, rather than protons, the principal charge carriers in metal wires? Protons are free to move through the metal, whereas electrons are fixed in place. Electrons are lighter, so they move faster than protons with the same kinetic energy. Electrons are free to move through the metal, whereas protons are fixed in place. Electrons are in the nucleus, whereas protons are in a cloud around the nucleus.
Electrons are free to move through the metal, whereas protons are fixed in place.
At what speed do electrons in a battery driven automotive circuit travel along a wire? At what speed does the electric field propagate along a wire? Electrons move at the speed of light. The electric field moves at 0.01 cm/s. Electrons travel at a few million km/hr. The electric field propagates at the speed of light. Electrons travel at 0.01 cm/s. The electric field travels instantaneously. Electrons move at 0.01 cm/s. The electric field propagates at nearly the speed of light.
Electrons move at 0.01 cm/s. The electric field propagates at nearly the speed of light.
When you make your monthly household electric payment, which of the following are you billed for: voltage, current, power, energy? Energy Voltage Power Current
Energy
A toaster has a heating element of 15 Ω and is connected to a 120-V outlet.Determine the current drawn by the toaster.
I=R/V I=15Ω/120V=8A
What is the current in a bulb if the resistance of its filament is 2 ohms and it is connected across a 6-volt battery? 3 amps 0.33 amps 12 amps
I=R/V I=2Ω/6V=3amps
Then, using the equation current = voltage/resistance, find the resistance of the toaster
I=RV R=7.86Ax140V≈17.8Ω
When the series combination of 8.0-Ω and 4.0-Ω resistors is impressed with 20 volts, how much current is in it?
I=V/Rtotal 20/12= 1.67A
What is the function of the round third prong in a modern household electric plug? It grounds the case to zero potential. It attaches the case to 120 volts potential. It provides safety against lightning strikes. It supplies a backup source of voltage.
It grounds the case to zero potential.
Does heating a metal wire increase or decrease its electrical resistance? Why? It decreases resistance because higher temperatures free more electrons to carry current. It increases resistance because atoms at higher temperatures jostle into the way of moving electrons. It decreases resistance because a metal becomes a superconductor when warmed. It decreases resistance because atoms at higher temperatures jostle into the way of moving electrons.
It increases resistance because atoms at higher temperatures jostle into the way of moving electrons.
If the resistance of a circuit remains constant while the voltage across the circuit decreases to half its former value, what change occurs in the current? It is cut in half. It stays the same .It quadruples .It doubles.
It is cut in half.
What does the power company provide to our homes? It provides energy to move the electrons. It provides electrons that travel through the wire. It provides neither electrons nor the energy to move the electrons. It provides electrons and the energy to move the electrons.
It provides energy to move the electrons.
What is the unit of electrical resistance? Amp Amp per volt Ohm Volt
Ohm
Using the formula, power = current × voltage, find the current drawn by a 1100-W toaster connected to 140 V.
P=I×V I=140V1100W=7.857A
Calculate the power of a hair dryer that operates on 110 V and draws a current of 15 A.
P=V×I P=110V×15A=1650W
An electric toy draws 0.80 A from a 120-V outlet.Determine how much power the toy consumes.
P=V×I P=120V×0.80A=96W
The work done to separate opposite charges results in different values of energy per charge. What is this difference called? Resistance Potential difference or voltage Force Current
Potential difference or voltage
What is the relationship among electric power, current, and voltage? Power is current times voltage. Power is current divided by voltage. Power is voltage. Power is voltage divided by current.
Power is current times voltage.
What is the equivalent resistance of a pair of 8.0-Ω and 4.0-Ω resistors when connected in series?
Rtotal=R1+R2 Rtotal=8.0Ω+4.0Ω=12.0Ω
Does a battery produce dc or ac? Does the generator at a commercial power station produce dc or ac? The battery is ac; the generator is dc. Both are dc. The battery is dc; the generator is ac. Both are ac.
The battery is DC; the generator is AC.
How does the current change if you increase the resistance, keeping the voltage difference the same? The current increases. The current decreases. The current stays the same.
The current decreases.
If both are halved? The current is doubled. The current is halved. The current remains unchanged.
The current remains unchanged.
What is the effect on the current in a wire if both the voltage across it and its resistance are doubled? The current is halved. The current is doubled. The current remains unchanged.
The current remains unchanged.
What is meant by drift velocity? The velocity of the electric field in a wire. The random motions of electrons moving a few million km/hr. The net flow of electrons along a wire. The collision velocity between electrons in the wire.
The net flow of electrons along a wire.
How does the resistance of a thick piece of copper wire compare to the resistance of a thin piece of copper wire? The resistance of the thick piece is greater than that of the thin piece. The resistance of the thin piece is greater than that of the thick piece. Both the wire and narrow piece of copper provide the same resistance.
The resistance of the thin piece is greater than that of the thick piece.
What kind of current runs through the electric wiring in a home? alternating current direct current circular current
alternating current
What unit is represented by coulomb per second? ampere joule watt ohm
ampere
What factors does the resistance offered by a piece of conductor depend upon? neither the geometry nor the material of the conductor only the geometry of the conductor material of the conductor both the geometry and the material of the conductor
both the geometry and the material of the conductor
What type of field causes the electrons to do what they do in the wire? magnetic field electric and magnetic fields electric field
electric field
When the filament breaks in one lamp in a series circuit, other lamps in the circuit normally _________. continue glowing, but dimmer continue glowing, but slightly brighter absorb energy from the damaged lamp go out
go out
To connect a pair of resistors so that their combined (equivalent) resistance will be greater than the resistance of either one, should you connect them in series or in parallel? in series in parallel
in series
What unit is represented by watt⋅second? coulomb ohm watt joule
joule
A voltage source in a circuit provides electrical _________. force grounding pressure resistance
pressure
What unit is represented by joule per coulomb? watt ampere ohm volt
volt
