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# Physics 245 MC exam1

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Electric field lines
a. circle clockwise around positive charges
b. circle counter-clockwise around positive charges
c. radiate outward from negative charges
d. radiate outward from positive charges
d. radiate outward from positive charges
At twice the distance from a point charge, the strength of the electric field
a. is four times its original value
b. is twice its original value
c. is one half its original value
d. is one fourth its original value
e. cant answer without knowing the charge
d. is one fourth its original value
Two electrically neutral materials are rubbed together. One acquires a net negative charge. The other must
a. have lots of electrons
b. have gained electrons
c. have lost electrons
d. have gained protons
c. have lost electrons
If the magnitude of the charge on two identical charged bodies is doubled, the electrostatic force between the bodies will be
a. doubled
b. halved
d. unchanged
what happens to the resistance of a wire if its radius is doubled?
a. R is doubled
b. R is halved
c. R is quadrupled
d. R is quarted
d. R is quarted
On order to transmit electrical power with a minimum loss of power in the transmission lines, power company's use
a. high current
b. high voltage
c. it doesnt matter since power is current times voltage
d. both high voltage and high currents result in minimum loss
...
A volt is a
a. C/s
b. J/C
c. V/A
d. W/C
b. J/C
A proton and electron are in a constant electric field created by oppositely charged plates. You release the proton form the positive side and the electron from the negative side. When it strikes the opposite side which one has more kinetic energy?
a. proton
b. electron
c. both acquire the same kinetic energy
d. neither- there is no change of kinetic energy
e. they both acquire the same kinetic energy but with opposite signs
c. both acquire the same kinetic energy
A proton and an electron are in a constant electric field created by oppositely charged plates. You release the proton form the positive side and the electron from the negative side. Which particle has the greatest acceleration immediately after the release.
a. proton
b. electron
c. both have the same acceleration
d. there is no acceleration
b. electron
Two point charges are separated by 10 meter. If the distance between them is reduced to 5.0 meters, the magnitude of the electrostatic force exerted on each:
a. decreases to half its original value
b. increases to twice its original value
c. decreases to one quarter of its original value
d. increases to four times its original value
d. increases to four times its original value
Doubling the voltage across a given capacitor causes the energy stored in that capacitor to
b. double
c. reduce to one half
d. reduce to one fourth
What happens to the resistance of a wire if its cross- sectional area is doubled?
a. R is doubled
b. R is halved
c. R is quadrupled
d. R is quarted
b. R is halved
If the magnitude of the charge on two identical charged bodies is doubled, the electrostatic force between the bodies will be:
a. doubled
b. halved
d. uncharged
Two electrically neutral materials are rubbed together. One acquires a net negative charge, the other must..
a. have lost electrons
b. have gained electrons
c. have lost electrons
d. have gained protons
c. have lost electrons
Doubling voltage across a given capacitor causes the energy stored in that capacitor to
b. double
c. reduce to one half
d. reduce to one fourth
The kilowatt-hour (kWh) is a unit of
a. voltage
b. current
c. power
d. energy
d. energy
The plates of a parallel-plate capacitor are maintained with constant voltage by a battery as they are pulled apart. During this process, the amount of charge in the plates must..
a. increase
b. decrease
c. remain constant
d. either decrease or increase. There is no way to tell without additional information
b. decrease
An alpha particle (charge 2p, mass approximately 4mp) and an electron are in a constant electric field created by oppositely charged plates. You release the alpha particle from the positive side and the electron from the negative side. When it strikes the opposite side which one has more kinetic energy?
A. they both acquire the same kinetic energy but with opposite signs
B. both acquire the same kinetic energy
C. electron
D. alpha particle
A. they both acquire the same kinetic energy with opposite signs
A wire carries a steady current of 0.15 A over a period of 30 s. What total charge passes through the wire?

A.450 C
B. 4.5 C
C. 200 C
D. 0.15 C
B. 4.5C
Doubling the voltage across a given capacitor causes the energy stored in that capacitor to

B. double.

C. reduce to one half.

D. reduce to one fourth.
The plates of a parallel-plate capacitor are maintained with constant voltage by a battery as they are pulled apart. During this process, the amount of charge on the plates must

A. increase

B. decrease

C. remain constant

D. either decrease or increase. There is no way to tell without additional information
B. decrease
What is the magnitude of the acceleration of an electron that is in an electric field of 600 N / C?

A. 600 m / s2

B. 5.7 x 10`10 m / s2

C. 3.5 x 10`11 m / s2

D. 1.1 x 10`14 m / s2
D.1.1 x 10`14 m / s2
A 2.5 C charge is 10 m from a second charge, and the force between them is 1.0 N. What is the magnitude of the second charge?

A. 44 C

B. 100.0 C

C. 4.4 mC

D. 4.4 nC
D. 4.4nC
Electric field lines

A. radiate outward from positive charges.

B. circle counter-clockwise around positive charges.

C. circle clockwise around positive charges.

D. radiate outward from negative charges.
A. radiate outward from positive charges.
Which statement about equipotential lines is true.

A. They always run parallel to each other.

B. They cross perpendicularly to the electric field lines.

C. Their density tells you the strength of the potential.

D. They start on negative charges and end on positive charges.
B. They cross perpendicularly to the electric field lines
Which has the higher resistance, a 100-W light bulb or a 75-W light bulb? Assume that both light bulbs are designed to be connected to normal AC power.

A. 100-W light bulb

B. 75-W light bulb

C. resistance is the same

D. can not be determined
B. 75-W light bulb
If the rms AC voltage across a 500 ohm resistor is 120 V, what is the peak current (I0)?

A. .34 Amps

B. .48 Amps

C. 3.4 Amps

D. 2.4 Amps
A. .34Amps
At twice the distance from a point charge, the strength of the electric potential due to the charges is

A. one-half its original value.

B. one-fourth its original value.

C. can't answer without knowing the charge

D. twice its original value.
A. one-half its original value
In order to transmit electrical power with a minimal loss of power in the transmission lines, power companies use

A. it doesn't matter since power is current times voltage

B. both high voltage and high currents result in minimum loss

C. high current

D. high voltage
D.high voltage
Two copper wires have the same length but the second has twice the diameter of the first. If the resistance of the first is 10 ohms, the resistance of the second is

A. 20 ohms.

B. 40 ohms.

C. 2.5 ohms.

D. 5 ohms.
C. 2.5ohms
The electrical energy supplied by a battery comes from

A. Charge stored on two isolated plates.

B. The heat produced by an exothermic reaction.

C. Chemical energy.

D. The magnetic force between two different metals.
C. chemical energy
A resistor is ohmic if its resistance

A. changes proportionally to the voltage.

B. changes proportionally to the current.

C. does not change with voltage or current.

D. decreases with temperature.
C. does not change with voltage or current
The absolute potential at the exact center of a square is 8.0 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 each of the other corners is also filled with a charge of +Q?
A. zero
B. 64 V
C. 32 V
D. 2 V
C. 32V
A wire carries a steady current of 0.3 A over a period of 30 s. What total charge passes through the wire?
A. 9.0 C
B. 90.0 C
C. 300 C
D. 0.3 C
A. 9.0 C
Doubling the voltage across a given capacitor causes the energy stored in that capacitor to
A. reduce to one fourth.
B. double.
C. reduce to one half.
The plates of a parallel-plate capacitor are maintained with constant voltage by a battery as they are pushed closer together (but not touching). During this process, the amount of charge on the plates must
A. increase
B. decrease
C. remain constant
D. either decrease or increase. There is no way to tell without additional information
A. increase
What is the magnitude of the acceleration of a proton that is in an electric field of 300 N / C?
A. 5.3 x 10`13 m / s2
B. 5.7 x 10`10 m / s2
C. 2.9 x 10`10 m / s2
D. 9.6 x 10`17 m / s2
C. 2.9 x 10'10 m / s2
Two point charges are separated by 10 meters. If the distance between them is reduced to 5.0 meters, the magnitude of the electrostatic force exerted on each:
A. decreases to half its original value
B. increases to twice its original value
C. decreases to one quarter of its original value
D. increases to four times its original value
D. increases to four time its original value
Electric field lines
A. radiate outward from negative charges.
B. circle counter-clockwise around positive charges.
C. circle clockwise around positive charges.
D. radiate outward from positive charges
D, radiate outward from positive charges
Which of the following statements is true.
A. Electric field lines cannot cross, but equipotential lines may cross.
B. Both electric field lines and equipotential lines may cross.
C. Both electric field lines equipotential lines can not cross.
D. Electric field lines can cross but equipotential lines cannot cross.
C. both electric field lines are equipotential lines can not cross
Two charges lie along the x axis at x=1 and x=10. The charge at x=1 is -2 C and the charge at x=10 is +5 C. Where will the electric field due to these two particles be zero?
A. To the right of x=10.
B. Between x=1 and x=10.
C. To the left of x=1.
D. Both between x=1 and 10 and below x=1.
C. to the left of x=1
Two copper wires have the same diameter but the second has twice the length of the first. If the resistance of the first is 5 ohms, the resistance of the second is
A. 10 ohms.
B. 20 ohms.
C. 1.25 ohms.
D. 2.25 ohms.
A. 10 ohms
The electric potential V, due to a negative charge, is zero at infinity and
A. positive everywhere else.
B. negative everywhere else.
C. positive if a second negative charge is nearby.
D. negative if a second negative charge is nearby.
B. negative everywhere else
A resistor is ohmic if its resistance
A. is proportional to the voltage.
B. is proportional to the current.
C. does not change with voltage or current.
D. decreases with temperature
C. does not change with voltage or current
A parallel-plate capacitor consists of plates of area 1.5X10-4 m2 and separated by 1.0 mm. The capacitor is connected to a 12-V battery. How much energy is stored in the capacitor?
A. 9.6X10-11 J
B. 4.8X10-11 J
C. 9.6X10-14 J
D. 4.8X10-14 J
E. none of the above
A. 9.6X10-11 J
A parallel-plate capacitor consists of plates of area 1.5 X 10-4 m2 and separated by 1.0 mm. The capacitor is connected to a 12-V battery. What is the electric field between the plates?
A. 12 N/C
B. 1.2X10`2 N/C
C. 1.2X10`3 N/C
D. 1.2X10`4 N/C
E. none of the above
D. 1.2X10'4 N/C
An atomic nucleus has a charge of +40e. An electron is 1.00 x 10-9m from the nucleus. What is the force on the electron?
A. 2.9 x 10-9 N
B.. 3.7 x 10-9 N
C. 6.8 x 10-9 N
D. 9.2 x 10-9 N
E. none of the above
D. 9.2 x 10-9 N
A helium nucleus (Q=+2e) is accelerated from rest through a potential difference of 300 V. Its final kinetic energy is
A. 200 eV
B. 300 eV
C. 600 eV
D. 900 eV
E. none of the above
C. 600eV
Two point charges of +3.00 C and -3.00 C are separated by a distance of 4.00 m. What is the electric field at a point midway between the two charges?
A. zero
B. 3.38x10`3 N/C
C. 6.75x10`4 N/C
D. 1.35x10`4 N/C
E. none of the above
D. 1.35x10`4 N/C
What is the magnitude of the acceleration of an electron that is in an electric field of 200 N/C?
A. 600 m / s2
B. 5.7 x 1010 m / s2
C. 3.5 x 1013 m / s2
D. 9.6 x 10-17 m / s2
E. none of the above
C. 3.5 x 10-7 m / s2
How much work is done when 8.5x1018 electrons move through a potential difference of 9.0 V?
A. 12 J
B. 7.7 J
C. 1.4 J
D. 1.1 J
E. none of the above
A. 12 J
A cardiac defibrillator is used to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1400 J of energy. What is its capacitance?
A. 9.6x10-5 F
B. 1.1x10-4 F
C. 2.3x10-4 F
D. none of the above
B. 1.1x10-4 F
. If the rms AC voltage is 106 V, what is the peak voltage (V0)?
A. 75 V
B. 106 V
C. 120 V
D. 150 V
E. none of the above
D. 150V
What is the magnitude of the acceleration of a proton that is in an electric field of 600 N / C?
A. 600 m / s2
B. 5.7 x 10`10 m / s2
C. 3.5 x 10`11 m / s2
D. 9.6 x 10`17 m / s2
E. none of the above
B. 5.7 x 10`10 m/ s2
A force of 6.0 N acts on a charge of 3.0 C when it is placed in a uniform electric field. What is the magnitude of this electric field?
A. 18 x10`6 N/C
B. 2.0x10`6 N/C
C. 0.50x10`6 N/C
D. 130x10`6 N/C
E. none of the above
B. 2.0x10`6 N/C
A helium nucleus (Q=+2e) is accelerated from rest through a potential difference of 300 volts. Its final kinetic energy is
A. 200 eV
B. 300 eV
C. 600 eV
D. 900 eV
E. none of the above
D. 900 eV
A large flashlight uses a 15.0-W bulb connected to a 12.0 V battery, what current does it draw?
A. 0.800 A
B. 1.25 A
C. 180 A
D. 200 A
E. none of the above
B. 1.25 A
A parallel-plate capacitor consists of plates of area 1.5X10-4 m2 and separated by 1.0 mm. The capacitor is connected to a 12-V battery. What is the electric field between the plates?
A. 12 N/C
B. 1.2X10`2 N/C
C. 1.2X10`3 N/C
D. 1.2X10`4 N/C
D. 1.2X10`4 N/C
A wire carries a steady current of 0.10 A over a period of 20 s. What total charge passes through the wire?
A. 200 C
B. 20 C
C. 2.0 C
D. 0.20 C
E.. none of the above
C. 2.0 C
The absolute potential at the exact center of a square is 3.0 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 each of the other corners is also filled with a charge of +Q?
A. zero
B. 3.0 V
C. 9.0 V
D. 12 V
E none of the above
D. 12 V