Chapter 7, Earth Space Science
The current through a 10 ohm resistor connected to 1 120-V power supply is
12 A
The electric power of a lamp that carries 2 A at 120 V is
240 W
The power dissipated in a 4 ohm resistor carrying 3 A is
36W
When a 10-V battery is connected to a resistor, 2 A of current flow in the resistor. What is the resistor's value?
5 ohms
What is a galvanometer?
A galvanometer is a device that indicates electric current.
Between a kilowatt and a kilowatt-hour, which is a unit of energy and which is a unit of power?
A kilowatt is a unit of power and a kilowatt-hour is a unit of energy.
What is induced by the rapid alternation of an electric field?
A magnetic field is induced in any region of space in which an electric field is changing with time.
What produces a magnetic field?
A magnetic field is produced by moving electric charges.
What condition is necessary for a sustained flow of electric charge through a conducting medium?
A sustained flow of electric charge requires a device to maintain a difference in electric potential.
What is it called when the galvanometer is calibrated to read current?
Ammeter
What is induced by the rapid alternation of a magnetic field?
An electric field is induced in any region of space in which a magnetic field is changing with time.
What is meant by saying that charge is conserved?
Charge cannot be created or destroyed; it can only be transferred.
How is Coulomb's law similar to Newton's law of gravity?
Coulomb's law and Newton's law of gravity are the inverse-square laws.
Distinguish between DC and AC.
DC is an electric current that flows in one direction only; AC is an electric current that repeatedly reverses its direction.
How are magnetic poles different from electric charges?
Electric charges can be isolated, magnetic poles cannot
How is Coulomb's law different from Newton's law of gravity?
Electrical forces may be either attractive or repulsive, whereas gravitational forces are only attractive.
What condition is necessary for electric charge to flow from one end of a metal bar to another?
Electrical potential difference. The electric charge flows from the end with higher potential to the end with lower potential.
Why do electrons, rather than protons, make up the flow of charge in a metal wire?
Electrons are loosely attached to atomic nuclei; protons are locked in the atomic nuclei.
How is the rule for the interaction between magnetic poles similar to the rule for the interaction between electric charges?
In both interactions, opposites attract and likes repel.
Why is iron magnetic and wood is not?
Iron has magnetic domains; wood does not.
What kind of materials are the best conductors? Why are they so good at conducting electricity?
Metals are the best conductors because their atoms have one or more outer electrons that are loosely bound to their nuclei.
Coulomb's law is most similar to
Newton's law of gravity
What is the unit of electrical resistance?
Ohm
Which type of circuit is favored for operating several electrical devices, each independently of the other − series or parallel? Defend your answer.
Parallel circuit is better because turning off a device doesn't affect the other devices.
In an electrical circuit, the safety fuse is connected to the circuit in
Series
Which part of an atom is positively charged, and which part is negatively charged?
The proton has a positive charge and the electron has a negative charge.
How does the sum of the currents through the branches of a simple parallel circuit compare with the current that flows through the voltage source?
The sum of currents though parallel branches equals the current through the source.
Which has more resistance − a thick wire or a thin wire of the same length and made from the same material?
Thin wire
What is it called when it is calibrated to read voltage?
Voltmeter
Surrounding every moving electron is
an electrical and magnetic field
Rapid changes of a magnetic field includes
an electrical field
An electron and a proton
attract each other
Electrons move in an electrical circuit
by interacting with an established electric field
To say that electric charge is conserved is to say that electric charge
can neither be created nor destroyed
A material with a lit of free charged particles that easily flow through it when an electrical force acts on them is a
conductor
An ampere is a unit of electric
current
The term for a current that moves in one direction
direct current, dc
The fundamental force underlying all chemical reactions is
electrical
The source of a magnetic field is a moving
electron
In an electrically neutral atom the number of protons in the nucleus is equal to the number of
electrons that surround the nucleus
compared to the huge force that attracts an iron tack to a strong magnet, the force that the tack exerts on the magnet is
equally huge
Magnet A has twice the magnetic field strength of magnet B, and at a certain distance pulls on magnet B with a force of 100 N. The amount of force that magnet A on magnet B is
exactly 100 N
Alternating current is normally produced by
generator
When the filament breaks in one lamp in a parallel circuit, lamps in other branches of the circuit normally
goes out.
A material with very little or no charged particles and through which current does not easily flow is an
insulator
Compared to the resistance of two connected in series, the same two resistors connected in parallel have
less resistance
When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is
less than the resistance of either lamp`
Which has more resistance − a short wire or a long wire of the same thickness and made from the same material?
long wire
Magnetism is due to the motion of electrons as they
move around the nucleus, spin on their axes
A likely cause for the existence of Earth's magnetic field is
moving charges in the liquid part of Earth's core, great numbers of very slow moving charges in the Earth, convection currents in the liquid part of Earth's core.
The source of all magnetism is
moving electric charge
Voltage can be induced in a wire by
moving the wire near the magnet, changing the current in a nearby wire, moving a magnet near the wire
Rub electrons from your hair with a comb and the comb becomes
negatively charged
Which pole of a compass needle points to the south pole of magnet?
north pole
A wire carrying a current is normally charged
not at all
The units used to measure electrical resistance are called
ohms
The headlights, radio, and defroster fan in an automobile are connected in
parallel
The intensity of cosmic rays bombarding Earth's surface is largest at the
poles
Strip electrons from an atom and the atom becomes
positive ion
A positive ion has more
protons than electrons
A material that falls into the midrange of conductivity, since it posses few electrons that are free to move is a
semiconductor
