|
What condition is necessary for the flow of heat? What analogous condition is necessary for the flow of charge? |
A difference in temperature is needed for heat to flow. A difference in electrical potential is needed for charge to flow. |
|
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. |
|
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. |
|
What exactly is an ampere? |
The flow of one coulomb per second |
|
Name two kinds of practical "electric pumps." |
Batteries and automobile alternators |
|
How much energy is supplied to each coulomb of charge that flows through a 12-V battery? |
12 joules |
|
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 |
|
Does heating a metal wire increase or decrease its electrical resistance? Why? |
It increases resistance because atoms at higher temperatures jostle into the way of moving electrons. |
|
What is the unit of electrical resistance? |
Ohm |
|
If the voltage impressed across a circuit is held constant while the resistance doubles, what change occurs in the current? |
It is cut in half. |
|
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? |
t is cut in half. |
|
How does wetness affect the resistance of your body? |
Wet bodies have lower resistance. |
|
What is the function of the round third prong in a modern household electric plug? |
It grounds the case to zero potential. |
|
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 does it mean to say that a certain current is 60 Hz? |
It alternates back and forth 60 times a second. |
|
What property of a diode enables it to convert ac to pulsed dc? |
It is a one-way valve that allows electrons to in one direction only. |
|
A diode converts ac to pulsed dc. What electrical device smoothes the pulsed dc to a smoother dc? |
A capacitor |
|
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. |
|
Why does a wire that carries electric current become hot? |
Moving electrons collide with atoms, which transfers their kinetic energy to atomic motion. |
|
What is meant by drift velocity? |
The net flow of electrons along a wire. |
|
A tipped domino sends a pulse along a row of standing dominoes. Is this a good analogy for the way electric current, sound, or both travel? |
This is the way sound travels but not how electric current travels. |
|
What is the error in saying the source of electrons in a circuit is the battery or generator? |
Wires are full of mobile electrons. |
|
When you make your household electric payment at the end of the month, are you billed for voltage, current, power, or energy? |
energy |
|
Where do the electrons come from that produce an electric shock when you touch a charged conductor? |
Inside you |
|
What is the relationship among electric power, current, and voltage? |
Power is current times voltage. |
|
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. |
|
How does the heat emitted by lamps affect their efficiency? |
Heat emitted reduces the efficiency. |
|
In a circuit of two lamps in series, where the current through one lamp is 1 A, what is the current through the other lamp? Defend your answe |
1 amp. The same current flows through lamps in series. |
|
If a voltage of 6 V is impressed across the circuit in the preceding question and the voltage across the first lamp is 2 V, what is the voltage across the second lamp? Defend your answer. |
4 volts. The sum of the voltages across each lamp must add up to the total voltage across both lamps. |
|
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 |
|
How do the currents through the branches of a simple parallel circuit compare with the current in the voltage source? |
The sum of the currents in the branches equals the current through the source. |
|
What is the function of fuse or circuit breaker in a circuit? |
To prevent over loading the circuit with current |
Share This
Flashcard
