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41 Cards in this Set
- Front
- Back
The quantity (1/2)E0*E^2has the significance of:
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energy/volume
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Capacitors A and B are identical. Capacitor A is charged so it stores 4 J of energy and capacitorB is uncharged. The capacitors are then connected in parallel. The total stored energy in thecapacitors is now:
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2J
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To store a total of 0.040 J of energy in the two identical capacitors shown, each should have acapacitance of:
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1 uJ
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A battery is used to charge a parallel-plate capacitor, after which it is disconnected. Then theplates are pulled apart to twice their original separation. This process will double the:
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stored energy
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A parallel-plate capacitor has a plate area of 0.3m2and a plate separation of 0.1 mm. If thecharge on each plate has a magnitude of 5×10−6C then the force exerted by one plate on theother has a magnitude of about:
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5N
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A certain capacitor has a capacitance of 5.0μF. After it is charged to 5.0μC and isolated, theplates are brought closer together so its capacitance becomes 10μF. The work done by theagent is about:
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-1.25*10^(-6)
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A dielectric slab is slowly inserted between the plates of a parallel plate capacitor, while thepotential difference between the plates is held constant by a battery. As it is being inserted:
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the capacitance and the charge on the positive plate increase but the potential differencebetween the plates remains the same
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An air-filled parallel-plate capacitor has a capacitance of 1 pF. The plate separation is thendoubled and a wax dielectric is inserted, completelyfilling the space between the plates. As aresult, the capacitance becomes 2 pF. The dielectric constant of the wax is:
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4
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One of materials listed below is to be placed between two identical metal sheets, with no, airgap, to form a parallel-plate capacitor. Which produces the greatest capacitance?
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material of thickness 0.5 mm and dielectric constant 11
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Two capacitors are identical except that one isfilled with air and the other with oil. Bothcapacitors carry the same charge. The ratio of the electricfieldsEair/Eoilis:
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between 1 and infinity
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a parallel-plate capacitor, with air dielectric, is charged by a battery, after which the batteryis disconnected. A slab of glass dielectric is then slowly inserted between the plates. As it isbeing inserted:
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a force attracts the glass into the capacitor
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Two parallel-plate capacitors with the same plate separation but different capacitance areconnected in parallel to a battery. Both capacitors arefilled with air. The quantity that isNOT the same for both capacitors when they are fully charged is:
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charge on the positive plate
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Two parallel-plate capacitors with the same plate area but different capacitance are connectedin parallel to a battery. Both capacitors arefilled with air. The quantity that is the same forboth capacitors when they are fully charged is:
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potential difference
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Two parallel-plate capacitors with different plate separation but the same capacitance areconnected in series to a battery. Both capacitors arefilled with air. The quantity that is NOTthe same for both capacitors when they are fully charged is:
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electricfield between the plates
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Two parallel-plate capacitors with different capacitance but the same plate separation areconnected in series to a battery. Both capacitors arefilled with air. The quantity that is thesame for both capacitors when they are fully charged is:
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charge on the positive plate
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A car battery is rated at 80 A·h. An ampere-hour is a unit of:
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charge
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Current has units
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C/s
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Current has unit
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ampere
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The units of resistivity are:
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ohm-meter
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The rate at which electrical energy is used may be measured in
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watt
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Energy may be measured in
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watt-second
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Which one of the following quantities is correctly matched to its unit?
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Potential difference - J/C
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Current is a measure of:
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amount of charge that moves past a point per unit time
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A 60-watt light bulb carries a current of 0.5 A. The total charge passing through it in one houris:
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1800C
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A 10-ohm resistor has a constant current. If 1200 C of chargeflow through it in 4 minutes whatis the value of the current?
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15A
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Conduction electrons move to the right in a certain wire. This indicates that:
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he current density and electricfield both point left
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Two wires made of different materials have the same uniform current density. They carry thesame current only if:
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heir cross-sectional areas are the same
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A wire with a length of 150 m and a radius of 0.15 mm carries a current with a uniform currentdensity of 2.8×107A/m2. The current is:
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2A
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n a conductor carrying a current we expect the electron drift speed to be:
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much less than the average electron speed
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Two substances are identical except that the electron mean free time for substance A is twicethe electron mean free time for substance B. If the same electricfield exists in both substancesthe electron drift speed in A is
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twice that in B
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The current is zero in a conductor when no potential difference is applied because
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or every electron with a given velocity there is another with a velocity of equal magnitudeand opposite direction.
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The current density is the same in two wires. Wire A has twice the free-electron concentrationof wire B. The drift speed of electrons in A is:
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half that of electrons in B
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copper contains 8.4×1028free electrons/m3. A copper wire of cross-sectional area 7.4×10−7m2carries a current of 1 A. The electron drift speed is approximately:
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10−4m/s
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If J is the current density anddnAis a vector element of area then the integral$nJ·dnAover anarea represents:
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the current through the area
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If the potential difference across a resistor is doubled:
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only the current is doubled
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five cylindrical wires are made of the same material. Their lengths and radii arewire 1: lengthf, radiusrwire 2: lengthf/4, radiusr/2wire 3: lengthf/2, radiusr/2wire 4: lengthf, radiusr/2wire 5: length 5f, radius 2r Rank the wires according to their resistances, least to greatest.
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1 and 2 tie, then 5, 3, 4
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Of the following, the copper conductor that has the least resistance is:
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hick, short and cool
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A cylindrical copper rod has resistanceR. It is reformed to twice its original length with nochange of volume. Its new resistance is:
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4R
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The resistance of a rod does NOT depend on:
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he shape of its (fixed) cross-sectional area
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A certain wire has resistanceR. Another wire, of the same material, has half the length andhalf the diameter of thefirst wire. The resistance of the second wire is:
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2R
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A nichrome wire is 1 m long and 1×10−6m2in cross-sectional area. When connected to apotential difference of 2 V, a current of 4 A exists in the wire. The resistivity of this nichromeis:
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5×10−7Ω·m
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