PHY 2054: Physics II
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HITT scores were mailed over the weekend.
They will be mailed once a week.
Hopefully all webassign problems have been
solved. Please see me immediately after
the class if there is still an issue.
SI meetings have begun. See the course
website for time and place.
PHY 2054: Physics II
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About bicycle riding: If some one shows
you a trick, it means that,
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It is possible to do that trick
The person who showed you, can do the trick.
It does not mean that you can do the trick.
Practice it a lot of times and you can too.
PHY 2054: Physics II
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Potentials
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Capacitors
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equipotentials
Q = C ΔV
Arrangement in a circuit
PHY 2054: Physics II
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U = k q1 q2/r
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Force => work =>
change in K=>
change in Potential
energy
ΔU = Uf – Ui = -W =
- ΔK
Work done is path
independent. K+U =
constant.
PHY 2054: Physics II
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Electric Potential
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V = U/q = -W/q
Units of Joules/coulomb = volt
1 eV = e x 1V = 1.6 x 10-19 J
Also
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V = kq/r
Vf –Vi = -∫E.ds
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for uniform fields Vf – Vi = - E (xf – xi)
Add as a number
PHY 2054: Physics II
PHY 2054: Physics II
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Rank them by the magnitude of electric field
Which has the field pointed to the right
What does an electron do when released midway
HITT 1
A proton (+1.6 × 10−19 C) moves 10 cm on a
path in the direction of a uniform electric field
of strength 3.0 N/C. How much work is done
on the proton by the electrical field?
a. 4.8 × 10−20 J
b. −4.8 × 10−20 J
c. 1.6 × 10−20 J
d. zero
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PHY 2054: Equipotentials
PHY 2054: Physics II
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Vf-Vi = -∫ k q/r2 dr
Choose Vi = V (∞)=0
V(r) = kq/r
q1 = 12nC, q2 = -24nC
q3 = 31nC, q4 = 17nC
d = 1.3 m
PHY 2054: Physics II
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V = kpcosθ/r2 p = qd
E = -∂V/∂s = - …….
Uniformly charged disk
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V = Ez
Parallel Plate Capacitor
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Area A, separation d, charge ±q
ΔV = V+ - V- = +Ed = qd/ εoA
E = σ/εo
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ΔV = qd/ εoA = q/C
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Farad = coulomb/volt
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C = εoA/d