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SPH 4U
1.
Fields Review
Compare gravitational potential with electric potential (energy). Compare electric to magnetic
fields. Use graphs in your explanations, as well as formulae.
2. In one stage of being put into a stable high circular orbit at an altitude of 6.63 x 107 m above
Earth, a 1500 kg satellite is first put into a lower circular orbit 200 km above the surface.
a) How much work is required to put the satellite into the lower orbit?
4.83 x 1010 J
3
b) What is the escape velocity of the satellite in its lower orbit?
7.79 x 10 m/s
3. A charge Q1 (+9.0 x 10-9 C) is located 2.0 m to the left of a charge Q2 (+7.0 x 10-9 C). What is
the electric field at a point A, located 1.0 m to the right of Q 1 and 70 cm above the line joining
Q1 and Q2?
56 N/C 10 from V
4. An alpha particle has a positive charge of 2 e and a mass of 6.6 x 10-27 kg. With what velocity
would an alpha particle reach the negative plate of a parallel plate apparatus with a potential
difference of 2.0 x 103 V, if it started from rest,
a) next to the positive plate?
4.4 x 105 m/s
b) at the midpoint between the plates?
3.1 x 105 m/s
5.
a)
b)
c)
d)
e)
f)
An electron is in a near circular orbit of radius 2.12 x 10 -10 m about a proton.
What is the electric field at the position of the electron?
3.2x1010 N/C
What is the force on the electron?
-5.13x10-9 N
What is the electric potential at the position of the electron?
6.79 V
What is the potential energy of the electron?
-6.79 eV or -1.09x10-18 J
How much kinetic energy does the electron have?
3.4 eV or 5.4x10-19 J
How much energy does it take to ionize the hydrogen atom from this energy level (binding
energy)?
3.4 eV or 5.4x10-19 J
-ve
+ve
6. An electron is released from rest at the left-hand (negative) plate
in the diagram below. It accelerates through the electric field
e
between the parallel plates and passes through the hole in the
positive plate into the magnetic field going into the page.
a) If the potential difference between the plates is 12 V, how fast is
the electron moving when it exits the plates?
2.05 x 106 m/s
b) If the strength of the magnetic field is 0.30 T, what is the radius of the electrons circular
path in the magnetic field?
3.9 x 10-5 m
-
7. A proton is momentarily at rest between two parallel plates that are 1.6 cm apart and have an
electric potential difference of 240 V between them. The proton is located 0.40 cm from the
positive plate.
a) Draw a diagram of the setup showing the plates, the proton, electric field and electric force.
b) What is the electric field at the position of the proton?
1.5x104 N/C
-15
c) What is the electric force on the proton?
2.4x10 N
d) What is the electric potential at the position of the proton relative to the -ve plate?
180 V
e) What is the electric potential energy at the position of the proton?
180 eV or 2.88 x 10-17 J
f) With what velocity would the proton hit the negative plate?
1.86x105 m/s
g) Why do we ignore the effects of gravity in this problem?
Fg << FE
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