Physics II Chapter 17
A certain material is in a room at 27°C. If the absolute temperature (K) of the material is tripled, its resistance doubles. (Water freezes at 273 K.) What is the value for a, the temperature coefficient of resistivity?
.00017
certain material is in a room at 27 degrees C. if the absolute temperature (K) of the material is doubled, its resistance doubles. what is the value for alpha, the temperature coefficient of resistivity
0.001 (degrees C)^-1
resistor is connected to a battery with negligible internal resistance. if you replace the resistor with one that has twice the resistance, by what factor does the power dissipated in the circuit change
0.50
a 60-W light bulb is in a socke supplied with 120 V. what is the current in the bulb
0.50 A
a light bulb has resistance of 240 ohm when operating at 120 V. find the current in the light bulb
0.50 A
a copper cable needs to carry a current of 200 A with a power loss of only 3.0 W/m. what is the required radius of the copper cable
0.85 cm
if a lamp has a resistance of 120 ohms when it operates at 100 W, what is the current does it carry
0.91 A
a steam turbine at an electric power plant delivers 4500 kW of power to an electrical generator which converts 95% of this mechanical energy into electrical energy. what is the current delivered by the generator if it delivers 3600 V
1.2 x 10 ^3 A
by what factor is the resistance of a copper wire changed when its temperature is increased from 20 degrees C to 120 degrees C? the temperature coefficient of resisivity for copper= ?.9x10^-3
1.39
number 10 copper wire (radius=1.3 mm) is commonly used for electrical installations in homes. what is the voltage drop in 40 m of #10 copper wire if it carries a current of 10 A?
1.3V
a 500 W heater carries a current of 4.0 A. how much does it cost to operate the heater for 30 min if electrical energy costs 6.0 cents per kWh
1.5 cents
a nichrome wire has a radius of 0.50 mm and a resistivity of 1.5x10^-6 ohms x m. what is the resistance per unit length of this wire
1.9 Ohm/m
replacing a wire resistor with another of the same material and length but with three times the diameter will have the effect of changing the resistance by what factor
1/9
if a lamp has resistance of 120 ohms when it operates at 100 W, what is the applied voltage
110 V
a solar panel measures 80 cm x 50 cm. in direct sunlight, the panel delivers 3.2 A at 15 V. if the intensity of sunlight is 1000 W/m^2, what is the efficiency of the solar panel in converting solar energy into electrical energy
12%
If a 500-W heater carries a current of 4.00 A, what is the voltage across the ends of the heating element?
125 V
suppose that a voltage surge produces 140 V for amoment in a 120 V line. what will temporarily be the output of a 100 W light bulb assuming its resistance does not change
136 W
a tungsten wire is sued to determine the melting point of indium. the resistance of the tungsten wire is 3.000 ohms at 20 degrees C and increases to 4.850 ohms as the indium starts to melt. tungsten=4.50x10^-3 (degrees C)^-1. what is the melting temperature of indium
15 degrees C
a metallic conductor has a resistivity of 18 x 10 ^-6 ohm x m. what is the resistance of a piece that is 30 m long and has a uniform cross sectional area of 3.0 x 10 ^ -6 m^2
180 ohms
a wire carries a steady current of 0.1 A over a period of 20 s. what total charge passes through the wire in this time interval
2 C
the current in an electron beam in a cathode-ray tube is measure to be 70 mA. how many electrons hit the screen in 5.0 s
2.2x 10^15 electrons
metallic wire of cross sectional area 3.0x10 ^-6 m^2 carries a current of 6.0 A and has mobile charge density of 4.24 x 10 ^28 carries/m^3, what is the average drift velocity of the mobile charge carriers?
2.9 x 10 ^-4 m/s
If a metallic wire of cross sectional area 3.0 ´ 10-6 m2 carries a current of 6.0 A and has a mobile charge density of 4.24 ´ 1028 carriers/m3, what is the average drift velocity of the mobile charge carriers
2.9 x10^-4
a 20 ohm platinum wire at 20 degrees C with a temperature coefficient of resistivity of 3.9 x 10^-3 (degrees C)^-1 will have what resistance at 100 degrees C
26 ohms
Two cylindrical resistors are made of the same material and have the same resistance. The resistors, R1 and R2, have different radii, r1 and r2, and different lengths, L1 and L2. Which of the following relative values for radii and lengths would result in equal resistances?
2r_1=r_2 and 4L_1=L_2
a flashlight bulb operating at a voltage of 4.5 V has a resistance of 8.0 Ohms. how mnay electrons pass through the bulb filament per second
3.5 x 10 ^18
an 8.00 ohm resistor is dissipating 100 watts, what are the current through it and the difference of potential across it
3.54 A, 28.3 V
electric clothes dryer draws 15 A at 220 V. if the clothes put into the dryer have a ? of 7.0 kg when wet and 4.0 kg when dry, how long does it take to dry the clothes? assume all heat energy goes into vaporizing water
32 minutes
you measure a 25.0 V potential difference across a 5.00 ohm resistor. what is the current flowing through it
5.00A
a metal wire has a resistance of 25.00 ohms under room temperature conditions of 25 degrees C. when the wire is heated to 85 degrees C the resistance increases 0.75 ohms. what is the temperature coefficient of resistivity of this metal
5.0x10^-4 (degrees C)^-1
A 0.20-m-long metal rod has a radius of 1.0 cm and a resistance of 3.2 ´ 10-5 W. What is the resistivity of the metal?
5.0x10^-8 ohm x m
an electric car is designed to runoff a bank of 12 V batteries with total energy storage of 3.0 x 10 ^7 J. if the electric motor draws 6000 W in moving the car at a steady speed of 10 m/s, how far will the ar go before it is "out of juice"
50 km
Some superconductors are capable of carrying a ery large quantity of current. if the measured current is 1.00x10^5 A, how many electrons are movoing through the superconductor per second?
6.25x10^23
how long is a wire made from 100 cm^3 of copper if its resistance is 8.5 ohms? the resistivity of copper is 1.7 x 10 ^-5 ohm x m
7.1 m
a high voltage transmission line carries 1000 A at 700000 V. What is the power carreid by the line
700 MW
a water pump draws about 3.8 A when connected to 240 V. what is the cost of running the pump for 10 h
82 cents
if electrical energy costs 5.5 cents per kWh, what does it cost to heat 200 kg water from 15 degrees C to 80 degrees C?
83 cents
A light bulb, sold as long-lasting, is rated 100 W at 130 V. The "increased" lifetime comes from using it at 120 V. Assuming negligible change in resistance at the different voltage, what is its power consumption at 120 V?
85 W
A high voltage transmission line of diameter 2 cm and length 200 km carries a steady current of 1000 A. if the conductor is copper with a free charge density of 8 x 10^28 electrons/m^3, how long does it take one electron to travel the full length of the cable
8x 10^8 s
a metal wire has a resistance of 10.00 ohms at a temperature of 20 degrees C. if the same wire has a resistance of 10.55 ohms at 90 degrees C, what is the resistance when its temperatur is -20 degrees C
9.69 ohms
the quantity volt is equivalent to which of the following
J/C
two wires with the same resistance have the same diameter but different lengths. if wire 1 has length L_1 and wire 2 has length L_2, hwo do L_1 and L_2 compare if a wire 1 is made from copper and wire 2 is made from aluminum? the resistivy of copper is 1.7 x 10^-5 Ohm x m and the resistivity of aluminum is 2,82 x 10^-5 ohm x m
L_1=1. L_2
the number density of conduction electrons in a metal can be found from the density p (rho) of the metal, the mass permole M of the metal, the nubmer of conduction electrons per metal atom, and Avogadros number N_A. if we assume one conduction electron per atom, which of the following gives the number density of conduction electrons for a given metal
N_Ap(rho)/M
superconductivity was discovered by:
Onnes
the unit of electric resistance, the ohm, is equivalent to which of the following
V/A
The unit of electric current, the ampere is equivalent to which of the following
V/ohms
the unit for rate of the energy transformation, the watt, ina electric circuit is equivalent to which of the following
VxA
what current is flowing in a superconductor, which statement is not true
a battery is needed to keep the current going
when current is flowing in a superconductor, which statement is not true
a battery is needed to keep the current going
The size of the electric current in an electrical conductor is a function of which of the following?
all of the above choices are valid
which process will double the power given off by a resistor
doubling the current by making a resistance half as big
The resistivity of a material is doubled when heated a certain amount. What happens to the resistance of a resistor made of this material when heated the same amount.
it doubles
the resisitivity of a material is doubled when heated ac ertain amount. what happens to the resistance of a resistor made of this material when heated the same amount
it doubles
a resistor is made of a material that has a resistivity that is proportional to the current going through it. if the oltage across the resistor is doubled, what happens to the power dissipated by it
it increases by a factor of 2^3/2
If the current in a wire is tripled, what effect does this have on the electron drift velocity in the wire?
it triples
when an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field
must be parallel to the current flow
consider some material that has been cooled until it has become a superconductor. if it is cooled even further its resistance will
none of the above
if a certain resistor obeys Ohm's law, its resistance will change
none of the above, since resistance is a constant for the given resistor
materials having resistance changes as voltage or current varies are called
nonohmic
the temperature coefficient of resistivity is a quantity that is:
sometimes negative
a light bulb with a tungsten filament is attached to a source of variable voltage. as the voltage is increased on the bulb
the bulb's resistance increases
Wire A and Wire B are each carrying the same current. if the diamter of Wire A is twice the __ of Wire B, how does the drift velocity v_dA in Wire A compare to that in Wire B
v_dA=v_dB/4
which is not a force
voltage
the temperature coefficient of resistivity for a perfect ohmic material would be
zero
