PHY 112 ?s

Three capacitors are connected as shown in the figure. What is the equivalent capacitance between points A and B? A) 12 uF B) 4.0 uC C) 7.1 uF D) 1.7 uF E) 8.0 uF

D) 1.7 uF

If the length and diameter of a wire of circular cross section are both tripled, the resistance will be: A) unchanged B) tripled C) increased by a factor of 9 D) 1/3 of what it originally was E) 1/9 of what it originally was

D) 1/3 of what it originally was

When a dielectric material is introduced between the plates of a parallel-plate capacitor and completely fills the space, the capacitance increases by a factor of 4. What is the dielectric constant of the material that was introduced? A) 0.4 B) 1/4 C) 2 D) 4 E) None of the above

D) 4

An ideal parallel-plate capacitor has a capacitance of C. If the area of the plates is doubled and the distance between the plates is halved, what is the new capacitance? A) C/4 B) C/2 C) 2C D) 4C

D) 4C

X and Y are two initially uncharged metal spheres on insulting stands, and they are in contact with each other. A positively charged rod R is brought close to X as shown in part (a) of the figure. Sphere Y is now moved away from X, as shown in part (b). What are the final charge states of X and Y? A) Both X and Y are neutral. B) X is positive and Y is neutral. C) X is neutral and Y is positive. D) X is negative and Y is positive. E) Both X and Y are negative.

D) X is negative and Y is positive.

Two stationary point charges q1 and q2 are shown in the figure along with a sketch of some field lines representing the electric field produced by them. What can you deduce from the sketch? A) q1 is negative and q2 is positive; the magnitudes are equal B) q1 and q2 have the same sign; the magnitudes are equal C) q1 is positive and q2 is negative; the magnitude of q1 is greater than q2 D) q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2 E) q1 and q2 have the same sign; the magnitude of q1 is greater than q2

D) q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2

Which one of the following is not an electromagnetic wave? A) ultraviolet B) infrared C) radio waves D) sound waves E) gamma rays

D) sound waves

Three particles travel through a region of space where the magnetic field is out of the page, as shown in the figure. What are the signs of the charges of these three particles? A) 1 is neutral, 2 is negative, 3 is positive B) 1 is neutral, 2 is positive, 3 is negative C) 1 is positive, 2 is neutral, 3 is negative D) 1 is positive, 2 is negative, 3 is neutral E) 1 is negative, 2 is neutral, 3 is positive

E) 1 is negative, 2 is neutral, 3 is positive

Four resistors having resistances of 20 omega, 40 omega, 60 omega, and 80 omega, are connected in series across an ideal dc voltage source. If the current through this circuit is 0.5 A, what is the voltage of the voltage source? A) 20 V B) 40 V C) 60 V D) 80 V E) 100 V

E) 100 V

T/F: A compass points north because that is the Earth's North Magnetic Pole.

False

T/F: According to Lenz's law, the induced current in a circuit always flows to oppose the external magnetic flux through the circuit.

False

T/F: Doubling the capacitance of a capacitor that is holding a constant charge causes the energy stored in that capacitor to double.

False

T/F: For capacitors in series, the voltage across each capacitor is the same.

False

T/F: If the resistance in a constant voltage circuit is doubled, the power dissipated by that circuit will increase by a factor of two.

False

T/F: In an electromagnetic wave in free space, the electric and magnetic fields are parallel to one another and perpendicular to the direction of wave propagation.

False

T/F: Light or any EM wave can only be modeled as a particle.

False

T/F: The electric field inside of charged parallel plate capacitor is not uniform.

False

T/F: The electron volt (eV) is a unit of power.

False

T/F: The length of a certain wire is kept the same while its radius is doubled. The resistance of this wire does not change.

False

T/F: The resistivity of a material increases as the temperature goes up.

False

T/F: This dipole in a uniform electric field will not move. (picture)

False

T/F: Two identical bulbs in series will not have the same brightness.

False

T/F: Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in the opposite direction, the wires will be attracted toward each other.

False

T/F: Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at a point exactly between the two wires points upward.

False

T/F: Two protons are released from rest, with only the electrostatic force acting, their acceleration will keep increasing.

False

T/F: We observe that a moving charged particle experiences no magnetic force. From this, we can definitely conclude that no magnetic field exists in that region of space.

False

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

A) 0.10 A

A cordless phone operates at 900 MHz. What is the wavelength of the electromagnetic wave used by this phone? A) 0.33 m B) 3.3 m C) 3.3 mm

A) 0.33 m

An electronic component with a 17-omega resistor is rated for use at power levels not exceeding 14 W. How much current can safely flow through the component? A) 0.91 A B) 1.21 A C) 238 A D) 0.22 A

A) 0.91 A

The heating element of a toaster is a 5.4-m length of nichrome wire of diameter 0.48 mm. The resistivity of nichrome at the operating temperature of the toaster is 1.3x10^-6 omega*m. The toaster is designed to operate at a voltage of 120 V. How much power does it draw in normal operation? A) 370 W B) 360 W C) 380 W D) 400 W E) 410 W

A) 370 W

A radio transmitter is operating at an average power of 4.00 kW and is radiating uniformly in all directions. What is the average intensity of the signal 8.0 km from the transmitter? A) 4.97 B) 2.49 C) 0.00497 D) 0.00249

A) 4.97

Two electrons are 20.0 mm apart at closest approach. What is the magnitude of the maximum electric force that they exert on each other? A) 5.8x10^-25 N B) 2.3x10^10 N C) 2.3 N D) 5.8x10^-27 N

A) 5.8x10^-25 N

Four point charges of equal magnitude but with varying signs are arranged on three of the corners and at the center of the square of side d as shown in the figure. Which one of the arrows shown represents the net force acting on the center charge? A) A B) B C) C D) D

A) A

A conductor is placed in a steady external electric field. Which of the following statements are correct for this situation? (There could be more than one correct choice) A) The electric field is zero inside the conductor. B) All the free electrons go to the surface of the conductor C) The surface of the conductor is neutral D) The electric field just outside the surface of the conductor is parallel to the surface E) None of the above are correct

A) The electric field is zero inside the conductor. B) All the free electrons go to the surface of the conductor

A hydrogen atom consists of a proton and an electron. If the orbital radius of the electron increases, the electrical potential energy of the electron due to the proton: A) increases B) decreases C) remains the same D) depends on the zero point of the potential

A) increases

Four, unequal resistors are connected in a parallel with each other. Which one of the following statements is correct about this combination? A) the equivalent resistance is less than that of the smallest resistor B) the equivalent resistance is equal to the average of the four resistances C) the equivalent resistance is midway between the largest and smallest resistance D) the equivalent resistance is more than the largest resistance E) none of the above

A) the equivalent resistance is less than that of the smallest resistor

A proton having a speed of 3.0x10^6 m/s in a direction perpendicular to a uniform magnetic field moves in a circle of radius 0.20 m within the field. What is the magnitude of the magnetic field? A) 0.080 T B) 0.16 T C) 0.24 T D) 0.32 T E) 0.36 T

B) 0.16 T

The plates of a parallel-plate capacitor are maintained with constant voltage by a battery as they are pulled apart. What happens to the strength of the electric field between the plates during this process? A) It increases B) It decreases C) It remains constant D) It cannot be determined based on this information

B) It decreases

T/F: A capacitor stores separated charges and has a potential difference, but it has no emf.

True

The figure shows electrons passing through a resistor. The arrow shows the direction in which the electrons are moving. Which of the following statements are correct? A) The electrons are moving slower at point b than at point a. B) The electric potential is higher at point b than at point a. C) The electric potential is lower at point b than at point a. D) The speed of the electrons at point b is the same as it is at point a.

B) The electric potential is higher at point b than at point a. D) The speed of the electrons at point b is the same as it is at point a.

A coil lies flat on a level tabletop in a region where the magnetic field vector points straight up. The magnetic field suddenly grows stronger. When viewed from above, what is the direction of the induced current in this coil as the field increases? A) counterclockwise B) clockwise C) clockwise initially, then counterclockwise before stopping D) There is no induced current in this coil

B) clockwise

Suppose you have two capacitors and want to use them to store the maximum amount of energy by connecting them across a voltage source. You should connect them A) in series across the source B) in parallel across the source C) It doesn't matter because the stored energy is the same either way

B) in parallel across the source

T/F: A dielectric material such as paper is inserted between the plates of a capacitor as the capacitor holds a fixed charge on its plates. The electric field between the plates as the dielectric is inserted will become weaker.

True

T/F: A hydrogen nucleus, which has a charge +e, is situated to the left of a carbon nucleus, which has a charge +6e. Is it true that the electrical force experienced by the hydrogen nucleus is to the left, and the magnitude is equal to the force exerted on the carbon nucleus?

True

T/F: As more resistors are added in parallel across a constant voltage source, the power supplied by the source increases.

True

T/F: Electrically neutral objects cannot exert an electrical force on each other.

True

T/F: For a beam of light, the direction of polarization is defined as the direction of the electric field's vibration.

True

T/F: For different resistors in parallel the current through each resistors is not the same.

True

T/F: The amount of current in a circuit depends jointly on the battery's emf and the resistance of the circuit attached to the battery.

True

Kirchhoff's junction rule is a statement of A) the law of conservation of momentum B) the law of conservation of charge C) the law of conservation of energy D) the law of conservation of angular momentum E) Newton's second law

B) the law of conservation of charge

T/F: The direction of the force on a current-carrying wire in a magnetic field is perpendicular to both the current and the magnetic field.

True

T/F: The fundamental charge (e) is the magnitude of the charge of an electron or proton: e=1.6x10^-19 C.

True

T/F: The induced current generates its own magnetic field. This induced magnetic field opposes the change in flux.

True

T/F: When a current flows through a metal wire, the moving charges are electrons.

True

An ideal solenoid with 400 turns has a radius of 0.040 m and is 40 cm long. If this solenoid carries a current of 12 A, what is the magnitude of the magnetic field at the center of the solenoid? A) 16 mT B) 4.9 mT C) 15 mT D) 6.0 mT E) 9.0 mT

C) 15 mT

A very long straight current-carrying wire produces a magnetic field of 20 mT at a distance d from the wire. To measure a field of 5 mT due to this wire, you would have to go to a distance from the wire of A) 16d B) 8d C) 4d D) 2d E) d SQRT 2

C) 4d

At a distance d from a point charge Q, the energy density in its electric field is u. If we now go to a distance d/2 from the charge, what is the energy density at the new location? A) 16u B) 8u C) 4u D) 2u E) u SQR of 2

C) 4u

How much energy is carried by a photon of light having frequency 110 GHz? A) 1.1x10^-20 J B) 1.4x10^-22 J C) 7.3x10^-23 J D) 1.3x10^-25 J

C) 7.3x10^-23 J

The maximum torque on a flat current-carrying loop occurs when the angle between the plane of the loop's area and the magnetic field vector is A) 0 B) 45 C) 90 D) 135

C) 90