Phys 241 Lecture quizzes
True or False? The net outward electric flux passing through any closed surface is equal to the net charge enclosed by the surface divided by a constant.
-x
I wish to use a step up transformer to turn an initial RMS AC voltage of 100 V into a final RMS AC voltage of 200 V. What is the ratio of the number of turns in the primary to the secondary?
1/2
Suppose I perform the double slit experiment with radio waves of wavelength lambda = 1 m and a pair of slits with separation D = 1 m. What is the theoretical maximum number of bright spots that I could possibly see?
1?
Suppose I produce radio waves with an antenna that have a peak electric field amplitude E and peak magnetic field amplitude B. If I were to double the amplitude of the electric field (i.e. double E) what is the new value for B?
2B
Suppose I build a parallel plate capacitor with plate area A and plate separation D. I hook it up across a battery of voltage V and charge it up to some final charge Q. If I were to double the plate area (keeping everything else constant), what is the new charge on the capacitor?
2Q
Suppose I have a circular loop of wire with radius R. I run a current I through the loop and measure a magnetic field B at the center of the wire. If I double the radius of the wire and triple the current in the wire, what is the new magnetic field at the center of the wire?
3B/2
Suppose a capacitor of capacitance C is connected to a battery with voltage V. We measure the energy stored in the capacitor to be E. If we were to now double the voltage of the battery (keeping C the same), what is the new energy stored in the capacitor?
4E
Suppose we measure the energy stored in some inductor to be E when there is a current I running through it. If I double the current in the inductor, the new total energy will become _____.
4E
Suppose I have a conducting sphere of radius R. I place a net charge of +Q on the sphere. What is the charge density inside the sphere?
?
Suppose I have a spherical insulating shell with inner radius r and outer radius R. The shell has a uniformly distributed charge of +Q. What is the charge density on my shell
?
Two parallel wires carry equal current in the same direction. Will the wires attract or repel each other?
Attract
Suppose I hook ten capacitors (each of capacitance C) in series. What is the net capacitance of the circuit?
C/10
Suppose I have a current-carrying loop of wire with some magnetic dipole moment mu or micro. I place it in a uniform magnetic field of strength B. Which of the following adjustments to the system would DECREASE mu or micro?
Decrease the current in the wire (I)
Suppose I am viewing light through a camera lens (i.e. a circular aperture). If I want a wider field of view I should _____ the diameter of the lens.
Decrease?
Suppose I center a conducting sphere of charge (radius R, total charge +Q) at the origin. How much energy would it take to move a point charge (total charge +q) from the surface of the sphere (r = R) to the center of the sphere (r = 0)?
E=0
When I move a conductor through a magnetic field, the change in magnetic field creates a net change in magnetic flux. The EMF that is induced by this changing flux creates tiny motional currents that are called _______.
Eddy Currents
Suppose I have a uniform magnetic field pointing along the +z direction. I launch an electron in the -z direction with a velocity V. What is the magnitude of the net force on the electron?
F=0
True or False? A perfect electric dipole feels a net force in a uniform electric field.
False
True or False? Electric field lines that are spaced close together imply a weak electric field
False
True or False? I build a velocity selector and use it to filter protons with a certain speed. Since it works for protons (positive charges), it will NOT work for electrons (negative charges).
False
True or False? If I draw some imaginary surface in space (either open or closed), the net magnetic flux passing through the surface is zero.
False
True or False? If I have a constant electric field in some region of space, that implies the electric potential is zero.
False
True or False? If light traveling in one medium strikes the surface of another medium in which it travels more slowly (i.e. a larger n), there is no phase change in the reflected light.
False
True or False? In an RL circuit, the larger the value of R (i.e. the resistance of the circuit), the longer it takes the circuit to reach its final steady-state value (with all else being held constant).
False
True or False? Magnetic flux does depend on the strength of the magnetic field passing through some surface, but it does not depend on the angle that the field makes with that surface.
False
True or False? The time constant of an RC circuit tells us how much time it takes for the circuit to charge or discharge by 50%.
False
Which type of magnetism is associated with the formation of domains?
Ferromagnetism
We pass initially unpolarized light through a polarizing filter that is oriented at 60 degrees with respect to the horizontal. If the light had some initial intensity I, what is the intensity after it goes through the filter?
I/4?
I bring a positively charged rod near an uncharged metal sphere, but not touching. I then group the metal sphere, leaving the sphere with a net charge. This is called charging by
Induction
Suppose I have a resistor of some resistance R. If I were to double the length and double the cross-sectional area of the resistor, what is the new resistance?
R
Suppose I hook ten resistors (each of resistance R) in parallel. What is the net resistance of the circuit?
R/10
In optics, when a lens is not perfectly parabolic, rays that strike the lens far from the axis are bent much more than rays that strike the lens close to the axis. This means that not all of the rays will pass through the focus as we would like. This is called _______.
Spherical Aberration
Suppose I shine light on a thin film of soap (i.e. a bubble). Which of the following does NOT affect the size or the orientation of the colored bands seen in a soap bubble?
The intensity of light shining on the bubble
Suppose I create a two-slit interference pattern using light with some wavelength lambda and slits with some separation D. If I were to increase the slit separation D, what would happen to the interference pattern on the wall?
The pattern would compress
Suppose I create a two-slit interference pattern using light with some wavelength lambda and slits with some separation D. If I were to increase lambda, what would happen to the interference pattern on the wall?
The pattern would spread out
True or False? A diverging lens is sometimes called a negative lens because we use a negative value for the focal length in the thin-lens equation.
True
True or False? A plane mirror has it's focus infinitely far away from the surface of the mirror.
True
True or False? If I have a constant electric potential in some region of space, that implies the electric field is zero.
True
True or False? If I were to hook up an AC voltage source to a resistor, the voltage drop across the resistor would be in phase with the current in the circuit.
True
True or False? In a driven RLC circuit, the peak value for voltage does not occur at the same time as the peak value for current. They are separated by some phase angle delta.
True
True or False? Kirchhoff's loop rule states that the algebraic sum of the changes in electrical potential around a closed loop in a circuit must equal zero.
True
True or False? Maxwell added a term called displacement current to Faraday's Law of Induction.
True
True or False? The average magnitude of the Poynting Vector is also known as intensity.
True
True or False? The current passing through some surface is equal to the flux of the current density through the surface.
True
True or False? The electric field is zero inside a conductor in electrostatic equilibrium.
True
True or False? The electric field produced by a uniform, infinite plane of charge does not depend on the distance from the plane. True
True
True or False? The induced EMF due to a changing magnetic flux creates a new magnetic field that resists the changing magnetic flux.
True
True or False? The magnitude of the EMF produced in a generator depends on the speed at which the generator turns.
True
True or False? The net outward electric flux passing through any closed surface is equal to the net charge enclosed by the surface divided by a constant.
True
True or False? The surfaces of equal potential around an infinite charged plane are parallel to the plane (i.e. the surfaces never intersect the charged plane).
True
True or False? The wavelength of light changes when we pass between two materials with different indices of refraction.
True
True or False? The wavenumber is directly proportional to the wavelength of an electromagnetic wave.
True
True or False? Waves have the property of reversibility. This means that if we reverse the direction of a reflected ray on a mirror, it will go back along the original path of the incoming ray, but in the opposite direction.
True
True or False? When a dielectric material is inserted in between the plates of a parallel-plate capacitor, the electric field between the plates is weakened by the dielectric.
True
true or false? the electric force between two charges is inversely proportional to the square of the distance separating them.
True
I have a simple LC circuit with some angular frequency omega. If I were to double the value of the capacitance (C) and double the value of the inductance (L) in the circuit, the new angular frequency would be __________.
w/2
