A diode converts ac to pulsed dc. What electrical device smoothes the pulsed dc to a smoother dc? |
A capacitor |
An electric current of 5 amperes in a wire carries ___ |
5 coulombs per second |
Between a watt, a kilowatt, and a kilowatt-hour, which is a unit of power and which is a unit of energy? |
A watt is power, a kilowatt is power, and a kilowatt-hour is energy. |
What does it mean to say that a certain current is 60 Hz? |
It alternates back and forth 60 times a second. |
When the filament breaks in one lamp in a parallel circuit, lamps in other branches of the circuit normally |
continue glowing as brightly |
How does the heat emitted by lamps affect their efficiency? |
Heat emitted reduces the efficiency. |
Why does a wire that carries electric current become hot? |
Moving electrons collide with atoms, which transfers their kinetic energy to atomic motion. |
How does wetness affect the resistance of your body? |
Wet bodies have lower resistance. |
The electric resistance in a length of wire is doubled when the wire is _________. |
twice as long |
When you make your household electric payment at the end of the month, are you billed for voltage, current, power, or energy? |
energy |
Does a battery produce dc or ac? Does the generator at a commercial power station produce dc or ac? |
The battery is dc; the generator is ac. |
What is the error in saying the source of electrons in a circuit is the battery or generator? |
Wires are full of mobile electrons. |
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 through and voltage is impressed across a circuit. |
Will water flow more easily through a wide pipe or a narrow pipe? Will current flow more easily through a thick wire or a thin wire? |
Wide pipe and thick wire |
When your body undergoes electric shock, the source of moving electrons is ________ |
electrons already in your body |
What condition is necessary for the sustained flow of water in a pipe? What analogous condition is necessary for the sustained flow of charge in a wire? |
A continuous pressure difference, often provided by a pump, is needed for water to flow. A continuous potential difference, often provided by a battery, is needed for charge to flow. |
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 0.01 cm/s. The electric field propagates at nearly the speed of light. |
In a circuit of two lamps in parallel, where there is a voltage of 6 V across one lamp, what is the voltage across the other lamp |
6 volts |
When the filament breaks in one lamp in a series circuit, other lamps in the circuit normally ___ |
go out |
Electric power in a circuit is the rate at which __ |
energy dissipates |
The entity that travels about the speed of light in an electric circuit is __ |
electric field |
A voltage source in a circuit provides electrical _________ |
pressure |
What is the function of fuse or circuit breaker in a circuit? |
To prevent over loading the circuit with current |
What is meant by drift velocity? |
The net flow of electrons along a wire. |
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. |
Why are electrons, rather than protons, the principal charge carriers in metal wires? |
Electrons are free to move through the metal, whereas protons are fixed in place. |
Name two kinds of practical "electric pumps." |
Batteries and automobile alternators |
Mastering Physics Electric Current
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