Test 1 College Physics
The monthly (30 days) electric bill included the cost of running a central air-conditioning unit for 2.0 hr/day at 5000 W, and a series connection of ten 60 W light bulbs for 5.0 hr/day. How much did these items contribute to the cost of the monthly electric bill if electricity costs 8.0¢ per kWh?
$31.20
The net work done in moving an electron from point A at -50. V to point B at +50. V along the semi-circle path shown in Fig. 16-3 is
-1.6 × 10-17 J.
The length of a certain wire is halved while the radius is doubled. What is the change in the resistance of this wire?
It is reduced by a factor of 8.
A surface on which all points are at the same potential is referred to as
an equipotential surface
The electron-volt (eV) is a unit of
energy
An equipotential surface must be
perpendicular to the electric field at any point
Fig. 16-1 shows three capacitors connected to a battery. The capacitances are such that C1 = 2C2 and C1 = 3C3. Which capacitor stores the smallest amount of charge?
All three capacitors store the same amount of charge.
Two point charges of magnitude +4.00 μC and -6.00 μC are placed along the x-axis at x = 0 cm and x = 40.0 cm, respectively. Where must a third charge, q, be placed along the x-axis so that it does not experience any net force because of the other two charges?
-1.78 m
A carbon resistor has a resistance of 18 Ω at a temperature of 20°C. What is its resistance at a temperature of 120°C? (The temperature coefficient of resistivity for carbon is -5.0 × 10-4 /C°.)
17 ohms
A kilowatt-hour is equivalent to
3,600,000 J
When a dielectric material is introduced between the plates of a parallel plate capacitor the capacitance increases by a factor of 4. What is the dielectric constant of the material introduced between the plates?
4
A negative charge is moved from point A to point B along an equipotential surface. Which of the following statements is true for this case?
No work is required to move the negative charge from point A to point B
If you connect two identical storage batteries together in series ("+" to "-"), and place them in a circuit, the combination will provide
twice the voltage, and the same current will flow through each.
Which of the following makes an approximate uniform electric field?
very large, closely separated, parallel oppositely charged plates
Two point charges of +6.00 μC and +9.00 μC are placed inside a cube of edge length 0.100 m. The net electric flux due to these charges is given by
1.69 × 10^6 Nm2/C
A brass key has a net positive charge of +1.92 × 10-16 C. Approximately, how many electrons must be added to the key to make it electrically neutral?
1200
A 24-kW electric furnace is connected to a 240-V line. What is the resistance of the furnace?
2.4 ohms
A 2.0 mm diameter wire of length 20 m has a resistance of 0.25 Ω. What is the resistivity of the wire?
3.9 × 10^-8 Ωm
A point charge of +Q is placed at the centroid of an equilateral triangle, as shown in Fig. 15-1. When a second charge of +Q is placed at one of the triangle's vertices, an electrostatic force of 4 N acts on it. What is the magnitude of the force that acts on the center charge when a third charge of +Q is placed at one of the other vertices?
4 N
A parallel-plate capacitor has plates of area 0.20 m2 separated by a distance of1.0 mm. What is the strength of the electric field between these plates when this capacitor is connected to a 6.0 V battery?
6.0 N/mC
A light bulb operating at 110 V draws 1.40 A of current. What is its resistance?
78.6 Ohms
An atomic nucleus has a charge of +40e. An electron is 10-9 m from the nucleus. What is the force on the electron?
9.2nN
Which of the following will increase the capacitance of a parallel plate capacitor?
?
Which of the following expression(s) represents the electrical energy stored by a capacitor?
All of the expressions are correct
A capacitor consists of a set of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery that maintains a constant potential difference between the plates. A slab of a dielectric material is inserted in the region between the plates so as to completely fill it. What changes would you observe?
Both the charge in the capacitor and its capacitance would change.
? Consider two copper wires. One has twice the length of the other. How do the resistivities of these two wires compare?
Both wires have the same resistivity.
Which of the following will increase the capacitance between the plates of a parallel plate capacitor?
Introduce a dielectric material between the plates.
Appliances in the USA are designed to work on 110-120 V, whereas appliances in Europe operate on 220-240 V. What would happen if you tried to use a European electric shaver in this country?
It would barely work (or maybe not work at all), since the voltage here is too low to push enough current through the device.
Four unequal resistors are connected in a parallel circuit. Which one of the following statements is correct about this circuit?
The total resistance is less than the smallest resistor.
Four unequal resistors are connected in a series circuit. Which one of the following statements is correct about this circuit?
The total resistance is more than the largest resistor.
A solid block of metal is placed in a uniform electric field. Which statement is correct concerning the electric field in the block's interior?
There is no electric field in the block's interior.
A glass rod is rubbed with a piece of silk. During the process the glass rod acquires a positive charge and the silk
acquires a negative charge
A Coulomb per second is the same as
an ampere
Figure 19-13 shows four Gaussian surfaces surrounding a distribution of charges. Which Gaussian surfaces have an electric flux of +q/εo through them?
b
Two electric charges each equal to +Q, are separated by a distance d. If you make a graph of the electric potential as a function of the distance along the line connecting the two charges, the point exactly midway between the two charges would
be a relative minimum
A capacitor consists of a set of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery that maintains a constant potential difference between the plates. If the separation between the plates is doubled, the magnitude of the charge on the plates will
be cut in half
A capacitor consists of a set of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery that maintains a constant potential difference between the plates. If the separation between the plates is doubled, the magnitude of the electrical energy stored on the capacitor will
be cut in half
Several electrons are placed on a hollow conducting sphere. They
become uniformly distributed on the sphere's outer surface.
A dielectric material such as paper is placed between the plates of a capacitor holding a fixed charge. What happens to the electric field between the plates?
becomes weaker
By what method will a positively charged rod produce a negative charge on a conducting sphere that is placed on an insulating surface?
by means of induction
The work done in moving a positive charge against an electric field does not depend on the path chosen in moving the charge in that field. Based on the statement, what kind of force field is the electrostatic field?
conservative
A potential difference (V) is applied to the ends of an object causing a current (I) to flow through it. If the object obeys Ohm's law we can obtain the resistance by
dividing voltage by current.
Gaussian surfaces A and B enclose the same positive charge +Q. The area of Gaussian surface A is three times larger than that of Gaussian surface B. The flux of electric field through Gaussian surface A is
equal to the flux of electric field through Gaussian surface B.
When the current through a resistor is increased by a factor of 4, the power dissipated by it
increases by a factor of 16
A device obeying Ohm's law must have a resistance which
is constant
The electric field at the surface of a conductor is
perpendicular to the surface
When the magnitude of both interacting charges is increased by a factor of 2, the electrical forces between these charges is
quadrupled
The number of protons in the nucleus of an electrically neutral atom is equal to
the number of electrons surrounding the nucleus.
If you connect two identical storage batteries together in parallel, and place them in a circuit, the combination will provide
the same voltage and twice the total charge that one battery would.
Capacitance of capacitors depends upon
the space between the conductors, the geometry of the conductors, and the material between the conductors [all of these answers]