Physics II Exam 1
At a distance of one centimeter from an electron, the electric field strength has a value E. At what distance is the electric field strength equal to E/2?
1.4 cm
Using Gauss' law, find the approximate magnitude of the electric field at the center of a circular face of a solid cylinder that has a length of 0.050-m, a radius of 0.020m, and a uniform volume charge density p=2.0e-9C/m3.
11 N/C
A brass key has a net positive charge of +1.92e-16C. Approximately, how many electrons must be added to the key to make it electrically neutral?
1200
What is the magnitude of the electrostatic force that two electrons separated by 1.0 nm exert on each other?
2.3e-10 N
A total charge of -6.50mC is uniformly distributed within a sphere that has a radius of 0.150 m. What is the magnitude and direction of the electric field at 0.300m from the surface of the sphere?
2.89e5 N/C, radially inward
Using Gauss' law, find the approximate magnitude of the electric field at the surface of a cube that has 0.10-m sides and a uniform volume charge density p=2.0e-9 C/m^3.
23 N/C
A straight, copper wire has a length of 0.50m and an excess charge of -1.0e-5C distributed uniformly along its length. Find the magnitude of the electric field at a point located 7.5e-3m from the midpoint of the wire.
4.8e7 N/C
A single, positive test charge is brought near a dipole. Under what circumstances will the force exerted on the test charge by the dipole be given by F=de2/2piEz^3?
the test charge is very far from the dipole compared to the distance between the dipole charges
The drawing shows a hollow conducting sphere with a net positive charge uniformly distributed over its surface. A small negatively-charged object has been brought near the sphere as shown. What is the direction of the electric field at the center of the sphere?
to the right
Four charges are located on the corners of a square as shown in the drawing. What is the direction of the net electric field at the point labeled P?
toward the middle of the botom side of the square
A spherical Gaussian surface of radius R is surrounding a particle with a net charge q. If the spherical Gaussian surface is replaced by a cube, under what conditions would the electric flux through the sides of the cube be the same as through the spherical surface?
under all conditions
An electron traveling horizontally to the right enters a region where a uniform electric field is directed downward. What is the direction of the force exerted on the electron once it has entered the field?
upward
The a solid brass sphere of radius 3cm is placed 0.5m directly below a water faucet. The flow of water from the faucet is two liters per minute. How much water flows through the sphere each minute?
zero liters
Two point charges are stationary and separated by a distance R. Which of the following pairs of charges would result in the largest repulsive force?
+2q and +4q
Consider the conducting spheres labeled A, B, and C shown in the drawing. The spheres are initially charged as shown on the left then wires are connected and disconnected in a sequence shown moving toward the right. What is the final charge on sphere C at the end of the sequence?
+Q
Consider the conducting spheres labeled A, B, and C shown in the drawing. The spheres are initially charged as shown on the left, then wires are connected and disconnected in a sequence shown moving toward the right. What is the final charge on the sphere A at the end of the sequence?
+Q/3
Three identical conducting spheres on individual insulating stands are initially electrically neutral. The three spheres are arranges so that they are in a line and touching as shown. A negatively-charged conducting rod is brought into contact with sphere A. Subsequently, someone takes sphere C away. Then, someone takes sphere B away. Finally, the rod is taken away. What is the charge of the final charge, if any, of the three spheres?
- - -, all 3 are negative
A spherical shell has an outer radius of 0.10m and an inner radius of 0.040cm. Within the shell is a charge q=-2.0e-9C. What is the surface charge density on the outer surface of the shell?
-1.6e-8C/m^2
Two objects separated by a distance r are carrying a charge -q. The magnitude of the force exerted on the second object by the first is F. If the first object is removed and replaced with an identical object that carries a +4q, what is the magnitude of the electric force on the second object.
4F
The end of the garden hose is enclosed in a mesh sphere radius 4cm. If the hose delivers five liters per minute, how much water flows through the sphere each minute?
5.0 liters
Imagine two conducting spheres separated by one meter. Each sphere carries an excess charge of one coulomb. What is the magnitude of the electrostatic force that each sphere exerts on the other?
9.0e9 N
Consider the electric field lines shown in the drawing. Which of the following statements correctly describes this situation?
A and B are both negatively charged particles.
Consider what would happen if electric field lines could cross each other. What would it mean if two electric field lines were to cross?
A test charge placed at the intersection of two electric field lines would experience a force in two different directions/
A positively charged object is located to the left of a negatively charged object as shown. Electric field lines are shown connecting the two objects. The five points on the electric field lines are labeled A, B, C, D, and E. At which one of these points would a test charge experience the smallest force?
B
Glass is a very good electrical insulator. How is then possible that a glass rod can be charged by rubbing it with cloth?
Because the rod is an insulator the charge that is transferred to the surface of the rod has difficulty moving.
The smallest charge on a single particle has been measured to be 1.60e-19C. What can we conclude from the fact that no smaller charges have been measured?
Charge is conserved.
A positively charged object is located to the left of a negatively charged object as shown. Electric field lines are shown connecting the two objects. The five points on the electric field lines are labeled A, B, C, D, and E. At which one of these points would a test charge experience the largest force?
D
Consider the drawing, where the solid lines with arrows represent the electric field due to the charged object. An electron is placed at the point P and released from the rest. Which of the following vectors represents the direction of the force, if any, on the electron?
Down and left diagonal
Two parallel infinite sheets of charge carry equal charge distributions sigma of opposite sign. Which of the following expressions gives the electric field in the region between the infinite sheets?
E= sigma/Esubsigma
A metal sphere with a net charge Q is at the center of an insulating sphere of radius R. What magnitude of the electric field at a point located at r>R?
E=1/4piE0 * Q/r^2
An inifinte slab of electrically insulating material has a thickness t. The slab has a uniform volume charge density p. Which of the following expression gives the electric field at a point P at a depth t-d relative to the surface?
E=p(t-d)/E0
Two objects, A with charge +Q and B with charge +4Q, are separated by a distance r. The magnitude of the force exerted on the second object by the first is F. If the first object is moved to a distance 2r from the second object, what is the magnitude of the electric force on the second object?
F/4
Four charges are located on the corners of a square as shown in the drawing. What is the direction of the net electric field at the point labeled P?
There is no direction. The electric field at P is zero N/C/
Can an object carry a charge of 2.0e-19C?
No, because the charge is quantized.
A conducting shell with an outer radius of 2.5cm and an inner radius of 1.5cm has an excess charge of 1.5e-7C. What is the surface charge density on the inner wall of the shell?
None of the above: 1.5e-9 C/m^2 2.9e-10 C/m^2 4.8e-10 C/m^2 8.5e-9 C/m^2
When you calculate the electric flux through a Gaussian surface, of what are you determining the flow through the surface?
None of the above: charge, electric current, electric energy, electric field
When a particle with a charge Q is surrounded by a spherical Gaussian surface, the electric flux through the surface is Phi(s). Consider what would happen if the particle was surrounded by a cylindrical Gaussian surface or Gaussian cube. How would the fluxes through the cylindrical Phi(Cyl) and cubic Phi(cubic) surfaces compare to Phi(s)?
Phi(s)=Phi(Cyl)=Phi(Cubic)
As shown in the drawing, a positively charged particle remains stationary between particles A and B. The positively charged particle is one-quarter the distance between two other particles, as shown. What can be concluded from the situation?
The charge on A must be one-sixteenth as large as the charge on B
Gauss' law may be written phi= ..... .Which of the following statements concerning the charge q is true?
The charge q is the sum of all charges inside the Gaussian surface.
Consider the electric field lines shown in the drawing. Which of the following statements correctly describes this situation?
The electric field is due to particles that are both charged either positively or negatively
A large sheet of electrically insulating material has a uniform charge density sigma. Let's compare the electric field produced by the insulating sheet with that produced by a thin metal (electrically conducting) slab with sigma/2 charge density distributed on one large surface of the slab and sigma/2 distributed over the surface on the opposite side. How does the electric field at a distance d from each surface compare?
The electric field near the insulating sheet is the same as that near the conducting slab.
Consider the two charges shown in the drawing. Which of the following statements correctly describes the magnitude of the electric force acting on the two charges?
The force on q1 has the same magnitude as that of the force on q2.
Consider the two charges shown in the drawing. Which of the following statements correctly describes the direction of the electric force acting on the two charges?
The force on q1, points to the right and the force on q2 points to the left.
Two negatively-charged objects are located on the x-axis, equally distant from the origin as shown. Consider the electric field at point P1. How will that electric field change if a third object with a charge +q is placed at point P2? Note: The point P2 is the same distance from the origin as the point P1 and the magnitude of each of the charges is the same.
The magnitude of the electric field will decrease by 25%.
A charged particle is located at the center of a uniformly charged hollow sphere. What is the net electrostatic force on the charged particle?
The net electrostatic force on the particle will be zero newtons because the vector sum of all of the forces on it due to the charges on the sphere is zero, so they exert no force on it.
A charged particle is located at a distance R/2 from the center of a uniformly charged hollow sphere of radius R. What is the net electrostatic force on the charged particle?
The net electrostatic force on the particle will be zero newtons because the vector sum of all the forces on it due to the charges on the sphere is zero, so they exert no force on it
A positively-charged object is released from rest in a region containing a uniform electric field. Which one of the following statements concerning the subesequent motion of the object is correct?
The object will experience a constant acceleration and move in the direction of the electric field
In July, Joe set up his fixed array of solar panels to maximize the amount of electricity output from the array when the Sun was high in the sky. Unfortunately, Joe finds that the array doesn't operate as well during the winter months, even though there is nothing physically wrong with the array. What is the most likely cause of Joes' winter problem?
The sun is lower in the sky during the winter, so sunlight strikes the solar panels at an angle/
A uniformly charged rod with a linear charge density lambda is located along the y axis as shown. The rod extends to infinity in both directions. Which of the following expressions gives the magnitude of the electric field at a point P located a distance d from the rod on the x axis?
a)
Consider a line of charge of length L that has a linear charge density lambda that is located on the x axis beginning at x=d. Which one of the following expressions allows one to calculate the electric field at the origin?
c)
Two particles are separated by a distance d. Particle A has a charge +Q and particle B has a charge +3Q. At what distance from particle A along the line connecting particles A and B would you place a third charged particle such that no electrostatic force acts on it?
d/9
When a glass rod is rubbed with silk cloth, the rod becomes positively charged as
negative charges are trasnferred from the rod to the silk
Consider the five situations shown. Each one contains either a charge q or a charge 2q. A Gaussian surface surrounds the charged particle in each case. Considering the electric flux through each of the Gaussian surfaces, which of the following comparative statements is correct?
phi2=phi4>phi1=phi3
An initially electrically neutral conducting sphere is placed on an insulating stand. A negatively-charged glass rod is brought near, but does not charge the sphere. Without moving the rod, a wire is then attached to the sphere that connects it to earth ground. The road and wire are then removed simultaneously. What is the final charge on the sphere?
positive