Physics II conceptual questions
The electric potential of a point charge is dependent on what?
1/r dependence
Which of the following is the name of the physics law which allows you to find the magnetic field due to any electric current?
Biot-Savart LAw
Consider two capacitors with the same voltage going through them. C1 is filled with a dielectric and C2 is not. Compare the charge on each capacitor.
C1>C2
If a conducting sphere has a total charge of 28.3 C and a radius of 1.5 m, what is the surface charge density?
Q/A = 1
Consider a region of space in which the magnetic field goes vertically down into the ground. Now take an iron bar (a conductor) and move it horizontally through this field by holding one end of the bar in your hand with the bar parallel to the ground and spining around so that the bar moves from left to right. (You can try this at home to make sure you understand the question.) Which end of the bar becomes positively charged?
The end away from you.
A circuit has been used to charge a capacitor. The charged capacitor is removed and placed in series with a different resistor which has a resistance half that of the resistor in the charging circuit. Compare the time constant and maximum current during discharge of the capacitor to those when it was charging.
The time constant is shorter and the maximum current is higher.
Two types of cylindrical resistors are made of the same material and so have the same resistivity. Type 1 has twice the diameter of type 2, but hald the length of type 2. Which has the larger net resistance?
Type 2
Consider two capacitors with the same voltage going through them. C1 is filled with a dielectric and C2 is not. Compare the stored energy on each capacitor.
U1>U2
Consider a circular loop of wire oriented in a vertical plane in front of you so that you can see through the center of the loop. Now shove the south end of a bar magnet into the center of the loop. As the magnet enters the loop,
a clockwise current is induced in the loop
Consider a circular loop of wire oriented in a vertical plane in front of you so that you can see through the center of the loop. Now shove the north end of a bar magnet into the center of the loop. As the magnet enters the loop,
a counterclockwise current is induced in the loop.
Consider a straight wire which is coming out of the wall in front of you and which is parallel to the ground. If the wire carries a current which is directed toward you, then the magnetic field lines due to the current...?
are circular about the wire and point counterclockwise
Consider two wires positioned parallel to each other. If current is passed through these wires in the same direction then the two wires will
attract each other
A charge is placed on a spherical conductor of radius r1. This sphere is then connected to a distant sphere of radius r2 by a conducting wire. After the charges on the spheres are in equilibrium, how does the potential compare btwn the two spheres?
both spheres are at the same potential
A long straight moving wire is in the plane of a single-turn circular loop. If the loop is moving in the plane and toward the wore, what direction is the induced current in the loop?
clockwise
Which of the following statements best describes how the magnitude of the electric potential varies as one moves radially outward from a point charge?
decrease as one over the distance from the charge
For an infinitely long straight wire with current flowing in it, the magnetic field strength will
decrease as one over the distance from the wire
A charged parallel-plate capacitor is removed from a battery. If the plates are pulled apart to a larger separation, what happens to the capacitance?
decreases
A positive charge's electric potential energy increases or decreases when it moves in the direction of the electric field?
decreases
In an RL circuit how does decreasing the applied voltage affect the time constant?
decreases
Electric field lines point in the direction of increasing or decreasing electric potential?
decreasing
Consider a parallel plate capacitor formed by two square plates which have sides of length L and which are separated by a distance d. Which is more effective in creating a higher capacitance, doubling L or decreasing d to half its original value?
doubling L
The net flux through any closed surface is independent of the shape of the surface is the same amount of charge is enclosed. True or false?
false
True or false. Ohm's law is a fundamental law of nature.
false
An ohmic material is one in which
has a linear relationship between current and potential
In a parallel plate capacitor, the electric field between the plates is most uniform where?
in the middle
A charged parallel-plate capacitor is removed from a battery. If the plates are pulled apart to a larger separation, what happens to the energy stored in the capacitor?
increases
A charged parallel-plate capacitor is removed from a battery. If the plates are pulled apart to a larger separation, what happens to the potential difference?
increases
In an RL circuit how does increasing the inductance affect the time constant?
increases
In an RL curcuit how does decreasing the resistance affect the time constant?
increases
The change in electric potential energy in moving between two points is independent or dependent of the path taken?
independent
The relationship between the potential difference across a resistor and the current flowing through the resistor can best be described by Ohms's law as
linear
In determining the changes in potential as one goes around a closed loop, if the direction in which the loop is analyzed requires you to traverse a voltage source (battery) from the positive terminal to the negative terminal, then the change in potential is
negative
A square loop is placed in a uniform magnetic field with the plane of the loop making an angle of 60 degrees with the direction of the field. If a current is made to flow through the loop, the field exerts a net torque or force on the loop?
net torque
Can one use Gauss's law to calculate the electric field on an electric dipole?
no
A wire is strung horizontally between two posts so that the current through the wire points away from the observer. A magnetic field is then produced in the region of the wire so that it points toward the observer and parallel to the wire. The observer will see the wire defect in what direction?
not at all
Consider two pieces of wire. Both have the same length and are made from the same material but one has a diameter twice that of the other. The ratio of the resistance of the larger wire to the smaller wire is
one fourth
Which of the following words best describes the orientation between electric field lines and equipotential surfaces?
perpendicular
A charge q is placed a distance r from the origin, and a charge 2q is placed a distance 2r. There is a charge +Q at the origin. If all charges are positive, which charge, q or 2q, is at the higher potential?
q
inverse of the conductivity is the
resistivity
Electric potential and electric potential energy are vector or scalar quantities?
scalar
Which of the following Gaussian surfaces cannot be used to determine the electric field due to an infinite non-conducting plane of charge?
sphere
A charged parallel-plate capacitor is removed from a battery. If the plates are pulled apart to a larger separation, what happens to the charge?
stays the same
A charged parallel-plate capacitor is removed from a battery. If the plates are pulled apart to a larger separation, what happens to the electric field between the plates?
stays the same
description of electric flux
the number of electric field lines penetrating some surface
The electric field due to an infinite non-conducting plane of charge has...
the same magnitude everywhere
In an RL circuit, a resistor and an inductor are connected in series to a battery of voltage V. When a switch is closed to complete the circuit, it takes a time t for the current in the circuit to reach one half of its maximum value. If the battery is replaced with one which provides twice the voltage, the time needed to reach one half of its maximum current will be:
the same.
A charge q is placed a distance r from the origin, and a charge 2q is placed a distance 2r. There is a charge +Q at the origin. If all charges are positive, which charge, q or 2q, has the higher electrostatic potential energy?
the two charges have the same potential energy
An inductor is a device in which energy is stored in the magnetic field within the inductor. True or false.
true
The north pole end of a bar magnet is held near a positively charged piece of plastic. The plastic is ______________ by the magnet?
unaffected
A wire is strung horizontally between two posts so that the current through the wire points toward the observer. A constant magnetic field is then produced in the region of the wire so that it points from left to right. The observer will see the wire deflect
upward
A spherical shell is placed in a region of space in which there exists a uniform electric field. The electric flux through the surface of the spherical shell is
zero