Download AP C PHYSICS – UNIT 7 REVIEW (ELECTRIC POTENTIAL

AP C PHYSICS – UNIT 7 REVIEW (ELECTRIC POTENTIAL & CAPACITANCE)
MULTIPLE CHOIC E
MULTIPLE CHOICE ANSWERS: B, B, D, D, B, D, D, D, D, B, C
FREE RESPONSE:
1)
2) Two thin, concentric, conducting spherical shells, insulated from each other, have radii of
0.10m and 0.20m, as shown above. The inner shell is set at an electric potential of -100V , and
the outer shell is set at an electric potential of +100V, with each potential defined relative to the
conventional reference point. Let Qi and Qo represent the net charge on the inner and outer
shells, respectively, and let r be the radial distance from the center of the shells. Express all
algebraic answers in terms of Qi , Qo , r, and fundamental constants, as appropriate.
a) Using Gauss’s Law, derive an algebraic expression for the electric field E(r) for 0.10 m < r < 0.20 m .
b) Determine an algebraic expression for the electric field E(r) for r > 0.20 m .
c) Determine an algebraic expression for the electric potential V(r) for r > 0.20 m .
d) Using the numerical information given, calculate the value of the total charge QT on the two
spherical shells
e) Sketch the potential as a function of r.
3) A spherically symmetric charge distribution has net positive charge Q0 distributed
within a radius of R. Its electric potential V as a function of the distance r from the center
of the sphere is given by the following.
Express all algebraic answers in terms of the given quantities and fundamental constants.
For the following regions, indicate the direction of the electric field E(r) and derive an expression
for its magnitude.
i. r < R
____ Radially inward ____ Radially outward
ii. r > R
____ Radially inward ____ Radially outward
4) Given: In the circuit diagram below, the battery is 40V and that C1 = 2µF, C2 = 6µF, C3 =
0.5µF, and V1 = 10 V.
a) How much charge is on C1?
b) How much charge is on C2?
c) What is the voltage drop across C2?
d) What is the voltage drop across C3?
e) What is the voltage drop across Cx?
f) How much charge is on C3?
g) How much charge is on Cx?
h) What is Cx?
i) How much total energy is stored in the circuit?
j) What is the total capacitance present in this circuit
FREE RESPONSE ANSWERS
1ai)
b) The x-components of the field vectors cancel due
to symmetry of particles B and C
c)
aii)
aiii)
d) Take derivative of answer in ‘c’ and set to zero and
solve for y.
2a)
b)
c)
OR
d)
e)
3)
4) 20uC, 20uC, 10.3V, 26.7V, 26.7V, 13.3uC, 6.7uC, .25uF, 4x10-4J, 0.5uF