Midterm Study Guide Questions Multiple Choice

A

A 6.0-μF air capacitor is connected across a 100-V battery. After the battery fully charges the capacitor, the capacitor is immersed in transformer oil (dielectric constant = 4.5). How much additional charge flows from the battery, which remained connected during the process? A) 2.1 mC B) 1.7 mC C) 2.5 mC D) 1.2 mC E) 1.5 mC

C

A Nichrome wire is used as a heating element in a toaster. From the moment the toaster is first turned on to the moment the wire reaches it maximum temperature, the current in the wire drops by 20% from its initial value. What is the temperature change in the wire? The temperature coefficient for Nichrome is α = 0.0004 (°C)-1. A) 200°C B) 300°C C) 500°C D) 100°C E) 400°C

D

A battery has an internal resistance of 2 Ω. This battery delivers maximum power to a load resistor that has a value of A) zero ohms. B) 1 Ω. C) 4 Ω. D) 2 Ω. E) 8 Ω.

C

A charge of 12 C passes through an electroplating apparatus in 2.0 min. What is the average current? A) 0.24 A B) 0.60 A C) 0.10 A D) 1.0 A E) 6.0 A

E

A charge of 2.0 μC flows onto the plates of a capacitor when it is connected to a 12. V battery. How much work was done in charging this capacitor? A) 21. μJ B) 0.14 mJ C) 48. μJ D) 24. μJ E) 12. μJ

B

A charged particle moving along a direction perpendicular to the plane of a loop of current-carrying wire, and which passes through the loop's center, will experience A) a magnetic force perpendicular to its velocity. B) no magnetic force. C) a magnetic force parallel to the loop axis. D) a magnetic torque.

D

A conductor is placed in an electric field under electrostatic conditions. Which of the following statements is correct for this situation? A) The electric field is zero inside the conductor. B) The electric field on the surface of the conductor is perpendicular to the surface. C) All valence electrons go to the surface of the conductor. D) All of the other answers apply.

C

A copper wire of 1.0 cm2 cross-sectional area would have to be how long to have a resistance of 1.0 ohm? A) 5.9 × 102 m B) 5.9 m C) 5.9 Mm D) 5.9 × 104 m E) 5.9 km

B

A proton has a speed of 3.0 × 106 m/s in a direction perpendicular to a uniform magnetic field, and the proton moves in a circle of radius 0.20 m. What is the magnitude of the magnetic field? A) 0.040 T B) 0.16 T C) 0.080 T D) 0.32 T E) 0.24 T

D

A rectangular loop of wire of width 10 cm and length 20 cm has a current of 2.5 A flowing through it. Two sides of the loop are oriented parallel to a uniform magnetic field of strength 0.037 T, the other two sides being perpendicular to the magnetic field. The magnitude of the torque on the loop is A) 0.050 m∙N. B) 0.038 m∙N. C) 0.0093 m∙N. D) 0.0019 m∙N. E) 0.025 m∙N.

E

A small galvanometer coil of resistance R = 20 Ω and full-scale deflection at 1 mA is connected in series with a 4980 Ω resistance to build an analog voltmeter. What is the maximum voltage that this voltmeter can read? A) 3 V B) 50 V C) 1 V D) 10 V E) 5 V

C

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? A) The interior field points in a direction that is at right angles to the exterior field. B) The interior field points in a direction that is parallel to the exterior field. C) There is no electric field in the block's interior. D) The interior field points in a direction opposite to the exterior field.

E

A surface on which all points are at the same potential is referred to as A) a dielectric surface. B) a constant electric force surface. C) a constant electric field surface. D) an equivoltage surface. E) an equipotential surface.

B

A typical public utility (power company) supplies electricity at an approximate cost of A) 1.¢/kW ∙ h. B) 10.¢/kW ∙ h. C) $100./kW ∙ h. D) $10./kW ∙ h. E) $1./kW ∙ h.

B

At a certain point in space the electric potential is 20 V. A 4.0-μC charge is brought from infinity to that point. What is the electric potential energy of this charge at that point? A) 4.0 μJ B) 80 μJ C) -80 μJ D) -20 μJ E) 20 μJ

B

At a certain point in space there is a potential of 400 V. What is the potential energy of a +2-μC charge at that point in space? A) 400 J B) 8 × 10-4 J C) 80 × 10-6 J D) 800 J E) 200 J

D

At double the distance from a long current-carrying wire, the strength of the magnetic field produced by that wire decreases to A) 1/4 of its original value. B) 2/3 of its original value. C) 1/8 of its original value. D) 1/2 of its original value. E) 1/ √2 of its original value.

A

Breaking a bar magnet in half will produce A) two bar magnets. B) a single South magnetic monopole. C) a single North magnetic monopole. D) one North and one South monopole

C

Capacitance is εo A/d for A) parallel wires. B) concentric cylinders. C) parallel plates. D) all capacitors.

D

Capacitance of capacitors depends upon A) the geometry of the conductors. B) the material between the conductors. C) the space between the conductors. D) all of these answers. E) none of these answers.

C

Consider a uniform electric field of 50. N/C directed toward the East. If the voltage measured relative to ground at a given point in the field is 80. V, what is the voltage at a point 1.0 m directly East of the point? A) 30. kV B) 0.15 kV C) 30. V D) 15. V E) impossible to calculate from the information given

C

Consider point charges of +Q and +4Q, which are separated by 3 m. At what point, on a line between the two charges, would it be possible to place a charge of -Q such that the electrostatic force acting on it would be zero? A) 3 m from the +4 charge B) There is no such point possible. C) 1 m from the +Q charge D) 3/5 m from the +Q charge E) 1 m from the +4 charge

D

Consider two copper wires. One has twice the length of the other. How do the resistivities of these two wires compare? A) The shorter wire has twice the resistivity of the longer wire. B) The longer wire has four times the resistivity of the shorter wire. C) The longer wire has twice the resistivity of the shorter wire. D) Both wires have the same resistivity.

B

Electric field lines A) start on negative charges and end on positive charges. B) are closer together the stronger the field. C) are perpendicular to the lines of force. D) were discovered by Franklin. E) were invented by Isaac Newton.

A

Electromagnetic radiation of wavelength 0.3 pico-meters is which type? A) gamma rays B) visible C) ultraviolet D) FM-radio E) X-rays

D

Electrons carry a A) neutral charge. B) variable charge. C) positive charge. D) negative charge.

A

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? A) 4 B) 0.4 C) 2 D) 1/4 E) None of the other choices is correct.

A

When resistors are connected in parallel, we can be certain that A) the potential difference across each is the same. B) the power dissipated in each is the same. C) their equivalent resistance is greater than the resistance of any one of the individual resistances. D) the same current flows in each one.

C

When two or more capacitors are connected in parallel to a battery, A) the equivalent capacitance of the combination is less than the capacitance of any one of the capacitors. B) each capacitor carries the same amount of charge. C) the voltage across each capacitor is the same. D) all of the given answers E) none of the given answers

E

Which of the equations here is valid for the circuit shown in Fig. 18-4? A) -2 - I1 - 2I2 = 0 B) 6 - I1 - 2I2 = 0 C) 2 - 2 I1 - 2I2 - 4I3 = 0 D) 2 - I1 - 2 I2 = 0 E) 4 - I1 + 4I3 = 0

C

Which of the following is an accurate statement? A) The electric field at the surface of a conductor is not necessarily perpendicular to the surface in all cases. B) A conductor cannot carry a net charge. C) If a solid metal sphere carries a net charge, the charge will move to the sphere surface. D) If a solid metal sphere carries a net charge, the charge will be uniformly distributed throughout the volume of the sphere.

A

Which of the following makes an approximate uniform electric field? A) very large, closely separated, parallel oppositely charged plates B) two long parallel, closely separated, oppositely charged lines of charge C) a metal charged cylinder D) a very long line of positive charge E) a metal charged sphere

A

Which of the graphs in Fig. 17-5 indicates that a positive temperature coefficient is obeyed for the entire range shown? A) graph a B) graph b C) graph c D) graph d

B

Which of the graphs in Fig. 17-5 indicates that the material is likely a semiconductor A) graph a B) graph b C) graph c D) graph d

B

When a 60-W lightbulb is operating on a 120-V household line, what current does it draw? A) 120 J/C B) 0.5 A C) 40 J/C D) 1.414 A E) 2.0 A

B

A proton (being 1836 times heavier than an electron) gains how much energy when moving through a potential increase of one volt? A) 1. Joule B) 1. eV C) 1836. J D) 0 eV E) 1836. eV

E

A 12 mF capacitor is connected in series with a 4 mF capacitor, the combination being connected across a 6 V power supply. The charge on the 12 mF capacitor is A) 24 mC. B) 72 mC. C) 36 mC. D) 12 mC. E) 18 mC.

A

A 2.0 μF capacitor is charged through a 50,000. Ω resistor. How long does it take for the capacitor to reach 90% of full charge? A) 0.23 s B) 0.9 s C) 2.3 s D) 2.19 s E) 9.1 s

E

A 24-kW electric furnace is connected to a 240-V line. What is the resistance of the furnace A) 0.42 Ω B) 10 Ω C) 1000 Ω D) 100 Ω E) 2.4 Ω

D

1.0-C charge is 15 m from a second charge, and the force between them is 1.0 N. What is the magnitude of the second charge? A) 25 C B) 1.0 C C) 0.025 C D) 25 nC E) 10 nC

C

A 3. Ω resistor is connected in parallel with a 6. Ω resistor. This pair is then connected in series with a 4. Ω resistor. These resistors are connected to a battery. What will happen if the 3. Ω resistor burns out, i.e., becomes an infinite resistance? A) The current provided by the battery will not change. B) The power dissipated in the circuit will increase. C) The current in the 6. Ω resistor will increase. D) The current in the 4. Ω resistor will drop to zero.

A

A 4.0 μF and a 6.0 μF capacitor are connected in series across an 8.0-V DC source. What is the charge on the 6.0 μF capacitor? A) 19 μC B) 2.0 μC C) 25 μC D) 4.0 μC E) 12 μC

A

A 400-W computer (computer plus monitor) is turned on 8.0 hours per day. If electricity costs 10 cents per kWh, how much does it cost to run the computer annually? A) $116.80 B) $16.80 C) $1168.00 D) $146.00 E) $14.60

E

A 1 pF capacitor is connected in parallel with a 2 pF capacitor, the parallel combination then being connected in series with a 3 pF capacitor. The resulting equivalent capacitance is A) 5 pF. B) 4.5 pF. C) 6 pF. D) 3 pF. E) 1.5 pF.

E

A 10 microcoulomb charge is placed at the origin and a 20 microcoulomb charge is placed on the x-axis at x = 40 cm. If an electron is placed on the y-axis at y = 30 cm, what is the magnitude of the force it will experience? A) 2.46 × 10-14 N B) 4.92 × 10-13 N C) 1.23 × 10-13 N D) 0.615 × 10-13 N E) 2.46 × 10-13 N

C

A cyclotron operates at 10. MHz. What magnetic field is needed to accelerate protons? A) 0.12 T B) 0.25 T C) 0.66 T D) 0.25 Gauss E) 1.1 T

A

A flux of 4 × 10-5 Wb is maintained through a coil for 0.5 s. What emf is induced in this coil by this flux? A) No emf is induced in this coil. B) 4 × 10-5 V C) 6 × 10-5 V D) 2 × 10-5 V E) 8 × 10-5 V

E

A force of 10 N acts on a charge of 5.0 μC when it is placed in a uniform electric field. What is the magnitude of this electric field? A) 1000 MN/C B) 1.0 MN/C C) 50 MN/C D) 0.50 MN/C E) 2.0 MN/C

E

A galvanometer has an internal resistance of 100 Ω and deflects full-scale at 2.00 mA. What size resistor should be added to it to convert it to a milliammeter capable of reading up to 4.00 mA? A) 50.0 Ω in parallel B) 75.0 Ω in parallel C) 50.0 Ω in series D) 100 Ω in series E) 100 Ω in parallel

A

A galvanometer with a coil resistance of 40.0 Ω deflects full scale for a current of 2.0 mA. What series resistance should be used with this galvanometer in order to construct a voltmeter that deflects full scale for 50 V? A) 25 kΩ B) 35 kΩ C) 27 kΩ D) 29 kΩ E) 31 kΩ

B

A glass rod is rubbed with a piece of silk. During the process the glass rod acquires a positive charge and the silk A) acquires a positive charge also. B) acquires a negative charge. C) remains neutral. D) could either be positively charged or negatively charged. It depends on how hard the rod was rubbed.

A

A light bulb operating at a voltage of 120 V has a resistance of 200 Ω. What is the power? A) 72 W B) 100 W C) 7.2 W D) 60 W E) 14 x 10-3 W

D

A mass spectrometer needs A) only an electric field. B) only a magnetic field. C) a perpendicular gravitational field. D) perpendicular magnetic and electric fields. E) co-linear magnetic and electric fields.

C

A metal sphere of radius 2.0 cm carries a charge of 3.0 μC. What is the electric field 6.0 cm from the center of the sphere? A) 4.2 × 106 N/C B) 5.7 × 106 N/C C) 7.5 × 106 N/C D) 9.3 × 106 N/C E) 6.4 × 106 N/C

D

A parallel-plate capacitor has plates of area 0.20 m2 separated by a distance of 1.0 mm. What is the strength of the electric field between these plates when this capacitor is connected to a 6.0 V battery? A) 6.0 N/C B) 1.2 kN/C C) 3.0 kN/C D) 6.0 N/mC E) 12. N/C

C

A parallel-plate capacitor has plates of area 0.20 m2 separated by a distance of 1.0 mm. What is this capacitor's capacitance? A) 40. F B) 2.0 × 102 F C) 1.8 nF D) 0.35 nF E) 22. μF

E

A parallel-plate capacitor has plates of area 0.80 m2 separated by a distance of 3.0 mm. What is this capacitor's capacitance? A) 70 F B) 4.8 × 10-10 F C) 3.6 × 10-10 F D) 270 F E) 2.4 × 10-9 F

B

An analog ammeter able to have a 0.5 A maximum reading is to be built using a small coil of resistance R = 20 Ω, and full scale deflection at 1 mA. What resistance should be added to this coil and how should it be connected to the coil? A) 20.4 Ω in parallel B) 0.04 Ω in parallel C) 0.08 Ω in parallel D) 0.02 Ω in series E) 0.5 Ω in parallel

A

An atomic nucleus has a charge of +40e. What is the magnitude of the electric field at a distance of 1.0 m from the nucleus? A) 5.4 × 10-8 N/C B) 5.6 × 10-8 N/C C) 6.0 × 10-8 N/C D) 5.8 × 10-8 N/C E) 6.2 × 10-8 N/C

B

An electron moves with a speed of 8.0 × 106 m/s along the +x axis. It enters a region where there is a magnetic field of 2.5 T, directed at an angle of 60° to the +x axis and lying in the xy plane. Calculate the magnitude of the magnetic force on the electron. A) 2.8 × 10-10 N B) 2.8 × 10-12 N C) 3.2 × 10-12 N D) 3.2 × 10-10 N E) 0 N

B

An equipotential surface must be A) randomly oriented with respect to the electric field. B) perpendicular to the electric field at any point. C) equal to the electric field at any point. D) parallel to the electric field at any point.

A

An ideal ammeter should A) introduce a very large series resistance into the circuit whose current is to be measured. B) introduce a very small series resistance into the circuit whose current is to be measured. C) have a high coil resistance. D) consist of a galvanometer in series with a large resistor.

B

An unknown resistor is wired in series and an ammeter and a voltmeter are placed in parallel across both the resistor and the ammeter. This network is then placed across a battery. If one computes the value of the resistance by dividing the voltmeter reading by the ammeter reading, the value obtained A) could be anything. It depends on other factors. B) is greater than the true resistance. C) is less than the true resistance. D) is the true resistance.

B

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? A) It would probably work as well as it does in Europe, since it is the current rating, not the voltage rating, that matters. B) It would barely work (or maybe not work at all), since the voltage here is too low to push enough current through the device. C) This question cannot be answered without knowing the frequency used in Europe and in the USA, since this is the parameter that matters most in any electrical device that operates on alternating current. D) It would probably work as well as it does in Europe, since it is the power rating, not the voltage rating, that matters. E) It would probably overheat and burn up before very long.

C

As more resistors are added in parallel to a constant voltage source, the power supplied by the source A) does not change. B) increases for a time and then starts to decrease. C) increases. D) decreases.

E

Fig. 15-8 shows electric field lines near two electric point charges. If Q1 = -1 μC, what is the value of Q2? A) -1 μC B) +1 μC C) -2 μC D) 0 E) +2 μC

C

Fig. 15.5 shows four Gaussian surfaces surrounding a distribution of charges. Which Gaussian surfaces have no electric flux through them? A) a. B) b. C) c. D) b and c. E) b and d.

E

Fig. 17-1 is a symbol for which of the following? A) capacitor B) galvanometer C) battery D) fuse E) resistor

E

Fig. 17-2 is a symbol for which of the following A) voltmeter B) capacitor C) switch D) resistor E) battery

C

Fig. 19-4 shows two wires, in cross section, carrying 7.0 Amperes out of the page. Determine the total magnetic field, due to both wires, at point X midway between the wires. A) 0.29 Gauss B) 0.15 Gauss C) 0.0 Gauss D) 0.59 Gauss E) 0.79 Gauss

C

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 A) three times smaller than the flux of electric field through Gaussian surface B. B) nine times larger than the flux of electric field through Gaussian surface B. C) equal to the flux of electric field through Gaussian surface B. D) unrelated to the flux of electric field through Gaussian surface B. E) three times larger than the flux of electric field through Gaussian surface B.

B

If a solid metal sphere and a hollow metal sphere of equal diameters are each given the same charge, the electric field (E ) midway between the sphere center and the surface is A) greater for the solid sphere than for the hollow sphere. B) zero for both. C) greater for the hollow sphere than for the solid sphere. D) equal in magnitude for both, but one is opposite in direction from the other.

B

If you connect two identical storage batteries together in series ("+" to "-"), and place them in a circuit, the combination will provide A) zero volts. B) twice the voltage, and the same current will flow through each. C) the same voltage, and different currents will flow through each. D) the same voltage and the same current will flow through each. E) twice the voltage, and different currents will flow through each.

B

In Fig. 18-3, which of the following equations is true? A) V1 + I1 R1 + I2 R2 + V2 + I2 R3 = 0 B) V1 - I1 R1 + I2 R2 - V2 + I2 R3 = 0 C) V1 - I1 R1 - I2 R2 + V2 - I2 R3 = 0 D) V1 + I1 R1 - I2 R2 - V2 - I3 R4 = 0

A

In Fig. 18-3, which of the following relations is true? A) I1 + I2 + I3 = 0 B) -I1 + I2 + I3 = 0 C) I1 - I2 - I3 = 0 D) I1 + I2 - I3 = 0 E) I1 - I2 + I3 = 0

C

In a vacuum, the relative permeability is A) 8.99 × 109. B) 4π × 10-7 T/A-m. C) 1.0. D) zero. E) infinite.

A

In electricity, what quantity is analogous to the "acceleration of gravity" g (which is a force per unit mass)? A) electric field B) electric force C) an electric dipole D) electric potential E) electric charge

B

Increasing the resistance of a voltmeter series resistance A) allows it to measure a smaller voltage at full-scale deflection. B) allows it to measure a larger voltage at full-scale deflection. C) converts it to an ammeter. D) enables more current to pass through the meter movement at full-scale deflection.

C

James Clerk Maxwell presented the "complete" theory of electromagnetism as how many equations? ' A) 3 B) 1 C) 4 D) 5 E) 2

A

Three capacitors C1, C2, and C3 are connected to a battery as shown in Fig. 16-2. The three capacitors have equal capacitances. Which capacitor stores the most potential energy? A) C1 B) C3 C) C2 D) C2 or C3. They store the same amount of energy E) All three capacitors store the same amount of energy.

A

To be more effective, how should one shape the tip of a lightning rod? A) sharpened to a point B) flat (cut off perpendicular to the rod axis) C) with a rounded tip (hemispherical)

E

My electric razor operates on 120. v and requires 3.0 Amperes. How much current comes out after delivering 360. watts of power? A) 2.4 A B) 40. A C) 1.2 A D) 0. A E) 3.0 A

B

Two charged objects attract each other with a certain force. If the charges on both objects are doubled with no change in separation, the force between them A) quadruples. B) doubles. C) halves. D) becomes zero. E) increases, but we can't say how much without knowing the distance between them.

D

Several electrons are placed on a hollow metal sphere. They A) clump together on the sphere's outer surface. B) clump together on the sphere's inner surface. C) become uniformly distributed on the sphere's inner surface. D) become uniformly distributed on the sphere's outer surface.

D

The absolute potential at the center of a square is 3. V when a charge of +Q is located at one of the square's corners. What is the absolute potential at the square's center when a second charge of -Q is placed at one of the remaining corners? A) -12 V B) 6 V C) 12 V D) 0 E) -6 V

B

The charge carried by one electron is e = -1.6 × 10-19 C. The number of electrons necessary to produce a charge of -1.0 C is A) 1.6 × 1019. B) 6.3 × 1018. C) 6.3 × 109. D) 1.6 × 109. E) none of the above

A

The charge carried by one electron is e = -1.6 × 10-19 C. The number of excess electrons necessary to produce a charge of 1.0 C is A) 6.3 × 1018. B) 1.6 × 1019. C) 1.6 × 10 18. D) 6.3 × 106. E) 6.3 × 109.

B

The dielectric constant of a vacuum is A) εo. B) 1.00 C) 8.99 × 109. D) zero. E) 1000.

E

The earth's magnetic field at the magnetic equator is approximately A) 104 Gauss. B) 104 T. C) 10-3 T. D) 1/2 T. E) 10-5 T.

C

The electric field at the surface of a conductor is A) never zero. B) always zero. C) perpendicular to the surface. D) parallel to the surface.

C

The flux through a coil changes from 4 × 10-5 Wb to 5 × 10-5 Wb in 0.1 s. What emf is induced in this coil? A) 3 × 10-4 V B) 4 × 10-4 V C) 1 × 10-4 V D) 5 × 10-4 V E) 7 × 10-4 V

D

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? A) -0.180 m B) 0.180 m C) 1.78 m D) -1.78 m E) 0.200 m

E

Two point charges of magnitude 4.0 μC and -4.0 μC are situated along the x-axis at x 1 = 2.0 m and x 2 = -2.0 m, respectively. What is the electric potential at the origin of the xy-coordinate system? A) -48 × 103 V B) 36 × 103 V C) -36 × 103 V D) 48 × 103 V E) 0 V

B

The net direction in which electrons flow through a circuit is A) the direction of the conventional current. B) opposite of the direction of the conventional current.

A

Two point charges, initially 2.0 cm apart, experience a 1.0-N force. If they are moved to a new separation of 8.0 cm, what is the electric force between them? A) 1/16 N B) 16 N C) 2.0 N D) 1/4 N E) 4.0 N

C

The resistance of an object is defined as A) (current)/(voltage). B) (length)/(resistivity)(cross-sectional area). C) (voltage)/(current). D) (voltage)(current). E) (length)(resistivity)(cross-sectional area).

E

The source of the earth's magnetic field is thought to be due to the motion of charged particles in the earth's A) crust. B) mantle & crust. C) inner core. D) mantle. E) outer core.

A

The wavelength of a certain portion of microwaves is 40 mm. What is its frequency? A) 7.5 GHz B) 40 GHz C) 0.75 GHz D) 75 GHz E) 4.0 GHz

E

What are the magnitude and direction of the electric field at a distance of 1.50 m from a 50.0-nC charge? A) 200 N/C toward the charge B) 20 N/C away from the charge C) 20 N/C toward the charge D) 10 N/C away from the charge E) 200 N/C away from the charge

A

What is the force per meter on a straight wire carrying 5.0 A when it is placed in a magnetic field of 0.020 T? (The wire makes an angle of 27° with respect to the magnetic field lines.) A) 0.045 N/m B) 0.26 N/m C) 0.022 N/m D) 0.071 N/m E) 0.17 N/m