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PHYS 1260 FINAL EXAM 2024/ 2025 ACTUAL
QUESTIONS AND CORRECT ANSWERS
GRADED A+
An RLC circuit is connected across an AC power source. How are the max and rms voltages from the power source related?
Vmax=(sqrt2)Vrms
In an RLC series circuit, if the AC frequency is increased to a very large value, what value does the phase angle between the current and voltage approach?
90
3 loops of wire, 1 circular, 1 rectangular, and 1 square are made from identical lengths of wire. If the loops are in the same increasing magnetic field perpendicular to the plane of the coils, which loops has the greatest induced emf?
the circular one
In an LCR series circuit, xL>xC. The phase angle is 30 degrees. If the Ac frequency doubles, what is the magnitude of the resulting phase angle?
more than 30 degrees
An electromagnetic wave is made up of which of the following oscillating quantities?
electric and magnetic fields
Which of the following characteristics are held in common by both gravitational and electrostatic forces when dealing with either point masses or charges?
all of the above
A resistor is made of a material that has a resistivity that is proportional to the current going through it. If the voltage is doubled, what happens to the current going through it?
it increases by a factor of 2^(1/2)
A free electron is in an electric field. With respect to the field, it experiences a force acting:
anti-parallel
Equipotential surfaces around a point charge are:
spherical
A conducting spherical shell of inner radius r1 and outer radius r2 has a charge Q on it. An additional charge, also Q, is then added to the sphere. What is the resulting charge per unit area on the outer surface of the sphere?
Q/2pi(r2)^
When charge Q1 is placed at point P1, the resulting potential at point P is V1. When Q2 is placed at point P2 after Q1 is in position at P1, the resulting potential at P becomes V2. What is the potential at point P if charge Q1 is then removed?
V2-V
AD
The electric field at the surface of a positively charges conductor has a direction characterized by which of the following?
perpendicular outward and away from the charge
Which of the following best characterized electrical insulators?
charges on the surface don't move
The electric field associated with a uniformly charged hollow metallic sphere is the greatest at?
the sphere's outer surface
If the size of the charge value is tripled for both of two point charges maintained at a constant separation, the mutual force between them will be changed by what factor?
9
An uncharged spherical shell has a charge q carefully placed at its center through a small hole. The charge q does not touch the shell. What is the charge on the outer surface?
q
At which location will the electric field between the two parallel plates of a charged capacitor be the strongest in magnitude?
midway between the two plates nearest the senter
If two parallel, conducting plates have equal positive charge, the electric field line will:
leave both plates and go to inifinty
Super conductivity was discovered by:
Onnes
The quantity volt is equivalent to:
J/C
If the distance between two point charges is increased by a factor of three, the resultant potential energy is what factor times the initial potential energy?
1/
If the current in a wire is tripled, what effect does this have on the electron drift velocity in the wire?
it triples
A length L of wire has a voltage V across its ends while current I runs through the wire. If a voltage 3V were applied to another length of this same wire, what is the length of this second wire?
3L
If it takes time T for the average conduction electron to traverse the 1mm wire, how long does it take for such an electron to traverse the 2mm wire?
8T
Two wires are arranged so that wire A points North and wire B points east, the wires crossing at their midpoints. Which is true?
there are no forces, but the net force on each wire is zero
Three resistors are connected in series. Which expressed the total resistance of the three resistors?
RT=R1+R2+R
AD
A current in a solenoid with N turns creates a magnetic field inside the solenoid. The magnetic field strength is directly proportional to the
number of turns in the loop; current strength
Electrical charges and magnetic poles have many similarities but one difference is...
a magnetic pole cannot be isolated
A certain capacitor is charged to 10V and then at t=0, allowed to discharge through a resistor. There will be a certain time before the voltage reaches 5V. The time can be decreased by increasing?
none of the above
A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field. A deuteron has the same charge as the proton but has twice its mass. The ratio of the magnetic force on the proton to that on the deuteron is:
2
If R1 < R2 < R3, and if these resistors are connected in parallel in a circuit, which one has the highest current?
R
Three resistors R1, R2, and R3 are connected in parallel. Which expressed the total resistance of the three resistors connected in parallel?
RT=((1/R1)+(1/R2)+(1/R3))^- 1
237NP
A stationary Q is located in the magnetic field. The direction of the magnetic force on Q is?
there is no magnetic force
Which statement regarding the force of a magnetic field on a current-carrying wire is true?
all of the above are false
The magnetic pole of the Earth nearest the geographic North Pole corresponds to which of the following?
magnetic south pole
Three resistors, each of different value, are used in a circuit with a power source applying 12V. For which of the following resistor combinations is the total power supply greatest?
all three resistors in parallel
A triangular current has twice as many turns as the square coil. Which coil experience the greater torque when a 30 degree angle is made?
square coil
In circuits involving resistors and capacitors, the quantity 63% often arises. Which is equivalent to this quantity?
1-e^-
Which of the following expresses the total resistance across three resistors connected in parallel?
VT=V1=V2=V
When a light bulb is turned on, its resistance increases until it reaches operating temperature. What happens to the current in the bulb as it is warming up?
it decreases
AD
If a proton is released at the equator and falls toward Earth under the influence of gravity, the magnetic force on the proton will be toward the ____ assuming the magnetic field is directed toward the north at this location.
east
As the current is going from 10A in one direction to 10A in the other, in which direction is the induced current in this side of the square coil nearest to the straight line?
it is in the positive y-direction
How is the direction of propagation of an electromagnetic wave oriented relative to the associated E and B fields?
perpendicular to both E and B
The electric field E, in an electromagnetic wave, is oriented in what direction with respect to its associated magnetic field, B?
E perpendicular to B
The magnet moving past an object will produce eddy currents in the object if the object:
is a conductor
The induced current appears almost instantaneously for loops close together. How can this energy exchange happen?
it is done via an electromagnetic wave
The operation of an electric motor depends on which of the following effects?
the force acting on a current-carrying wire in a magnetic field
How is the energy stored in a current-carrying inductor related to the current value, I?
directly proportional to I^
By what factor is the self-inductance of an air solenoid changed if only its cross-sectional are, A, is multiplied by 8?
8
If the loop area increases, what effect does this have on the induced current?
the induced current is counterclockwise
Electricity may be generated by rotating a loop of wire between the poles of a magnet. The induced current is greatest when
the plane of the loop is parallel to the magnetic field
In an RLC circuit, the max current is 1 amp. What is the average current?
none of the above
The rms current is equal to the direct current that
dissipates an equal amount of energy in a resistor at the same rate as in an AC circuit
How is the energy stored in a current-carrying inductor related to its self-inductance, L?
directly proportional to L
position B
By what factor is the self-inductance of an air solenoid changed if its length and number of coil turns are both multiplied by 7?
7
By what factor does the max energy stored in a series RL circuit change if the resistance is doubled and the inductance is tripled?
The ideal transformer is one that:
experience no power loss
In an AC circuit, the current in a pure resistor differs in phase with the applied voltage by what angle?
zero
Transmitting power at high voltage (400,000 V), reduces the power loss for transmission lines. How then can 400,000 V be used in a normal house?
before reaching households, transformers are used to reduce the voltage appropriately
When voltage is generated by rotating a coil in a magnetic field, the period of the voltage equals the time that it takes for the coil to rotate through ______ radians.
2pi
If the induced current in a wire loop were such that the flux it produces were in the same direction as the change in external flux causing the current, which of the following conservation laws would end up being violated?
Energy
The units T*m^2/s are equivalent to:
V
A magnet is dropped so it falls lengthwise toward the center of the ring. Will the magnet be attracted to the ring or repelled by the ring?
it will be repelled
In a Young's double-slit interference apparatus, the distance from the slits to the screen is quadrupled. The distance between adjacent light and dark fringes changes by a factor of:
4
What is the critical angle for total internal refraction for a ray of light going from material 1 to 2?
45 degrees
Who formulated the theory explaining the photoelectric effect?
Einstein
A light ray incident on the interface between air and glass can undergo total internal reflection:
only in the glass
A slab of plastic rests on a slab of glass. A ray of light in the plastic interface crosses between plastic and glass, with the result that the ray bends normally. What must be true about the indices of refraction in these materials?
plastic < glass
What is the cause of refraction of a wave traveling from one medium to another?
there is a speed change due to the change in the medium
When the reflection of an object is seen in a concave mirror, the image will...
be either virtual or real
The magnification for a flat mirror...
is 1
When the midpoint of the face of the sun appears to be on the horizon, where is the actual midpoint from the view of the observer?
below the horizon
An object of length 3.00 cm is inside a plastic block with index of refraction 1.40. If the object is viewed through the top surface of the block at a non-zero angle from the normal, where is the object relative to its image?
below the direction of its image
Atmospheric refraction of light rays is responsible for...
mirages
You stand two feet away from a plane mirror. How far is it from you to your image?
4 ft
The lateral magnification for a flat mirror...
is 1
Which f the following effects is the result of the fact that the index of refraction of glass will vary with wavelength?
