Name______Student Number______
Last First MI
- Multiple Choice (4pts each) Fill in the most correct answer on the bubble sheet, and circle the correct answer on this page for future reference.
1)(5pts) An electron moves from right to left and is slowing down, away from any gravitational forces. What is the most correct statement?
a)The potential increases from left to right
b)The electric field is constant
c)The potential decreases from left to right
d)The electric potential is small
e)no explanation is known
2)From 1), what is the direction of the electric field?
a)From left to right
b)From right to left
c)Not enough information
d)No electric field
3)The plates on a parallel plate capacitor have a constant charge q. What happens to the potential energy as the plate separation is increased?
a)No change
b)increases
c)decreases
d)no potential energy in system
e)not enough information
4)Given a rod of length l and total charge q, what is the electric potential a large distance from the charge, assuming V at infinity is zero?
a)kq/l2
b)kq/(l-r)
c)kq/r
d)kq/r2
5)Anelectron accelerates to the left at a constant rate starting from rest through a distance of 0.65m in a time of 0.015s. What is the magnitude of the electric potential through which the electron moves, in 10-8V?
a) 0.92
b)1.07
c) 2.14
d)4.28
e) 19.2
6)From 5), what is the direction of the increase in the potential?
a)to the right
b)to the left
c)up
d)down
e)not enough information
7)A large square conductor is at a potential of 12V. The conductor has sides of length 3cm. What is the work done moving an electron from one corner of the cube, to the opposite corner, in Joules?
a)363
b)36
c)144
d)-363
e)none of the above
8) A circular disk has a surface charge density of =6r C/m3 and a radius of 1.4m. What is the total charge on the disk, in C?
a) 34.5
b) 16.4
c) 5.5
d) 3.2
e) no charge present
9)In the typical living cell the potential inside the cell is 0.070V lower than outside the cell. The thickness of the cell is 0.1micrometers. What is the direction and magnitude of the average electric field within the cell membrane, in units of 106?
a) 7.0
b)70.0
c) 0.70
d) 14.0
e) 0.14
10)(5pts)Given two charges Q=-15C at x=3cm, and q=10C at x=10cm, in which region is there a point at which the electric potential is zero? (ignore the value at infinity)
a)x<3
b)3<x<10cm
c)x>10cm
d)It will never be zero
11) From 10), if you were to move a distance away, x>5cm, what would the electric potential look like?
a)V=infinity
b)V=-k 5C/x2
c)V=-k 5C/x
d)V=-k 10C/x2
e)V=-k 10C/x
- Written Solution: 30 Points. Be sure to show all of your work for full credit.
A neutral conducting spherical shell of inner radius a and outer radius b, has a point charge Q in the center.
A)Find the potential as a function of r, the radius from the center, in region I outside of the shell.
Solution______
B)Find the potential as a function of r in region II, within the shell.
Solution______
C)Find the potential as a function of r in region III, inside of the shell.
Solution______
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Phys 122 exam 1 sum06