SPH3U: Conservation of Mechanical Energy - stpats-sph3u

```SPH3U: Electricity Generation, Mass-Energy Conversion
Read pp. 635-640, pp. 293-295; Do p. 302 – 39, 40
Faraday’s Law of Electromagnetic Induction (p. 608)
A moving magnetic field with respect to a conductor will produce an electric current in the
conductor
Most of the electricity generated in our society is done
so through the application of electromagnetic
induction:

Moving a magnet and a coil of wire with respect
to each other = electrical generator!

How to move the magnet/or coil? By turning a
turbine! (kinetic energy)
What energy sources are used to turn a turbine?
◊ falling water (potential energy)
◊ steam (from fossil fuels or nuclear energy)
Electricity Generation in Canada and Ontario
Energy-Mass Equivalence (more in Grade 12 Physics!)
In 1905, Albert Einstein proposed that mass and energy were in some way equivalent, as expressed by his
famous equation: E  mc 2 .
This equation predicted that enormous amounts of energy were possible by a conversion of a small
amount of mass. Nuclear energy is the energy stored in the nuclei of atoms that is released when nuclear
fission (heavy nucleus splits into smaller nuclei) or nuclear fusion (the joining of smaller nuclei into a
more massive nucleus) occurs.
Example:
If 1.0 kg of matter were completely converted into energy, how much would be produced? (For the
Read pp. 635-640; Do p. 663 - #14, #15
Atomic Notation Review:
A
Z
X - Element
Z – atomic # = # protons
A - mass # = # protons +
neutrons
X
Example:
222
86
# protons: 86
# neutrons:136
# electrons: 86
Rn
We can use the same notation to protons, neutrons, electrons and positrons (positively charged electrons):
Neutrons: 01 n
Protons: 11 p
Electrons:
0
1
e
Positrons:
0
1
e
Positively charged protons in atomic nuclei tend to repel each other. Nuclei require short range strong
nuclear forces between protons and neutrons to dilute the repulsion and act as a nuclear “glue”. Nuclei
having too few (or too many) neutrons are unstable and may release particles (radiation) in order to reach
(a) Alpha Decay:
A heavy nucleus decays, producing a smaller nucleus and an alpha particle (a helium nucleus, having 2
protons and 2 neutrons)
General Form:
A
Z
X 
A 4
Z 2
Y  24He (α)
Example (complete what’s missing):
226
88
Rn  24He
Ra 
(b) Beta Decay:
In the first case of beta decay, one neutron converts to a proton plus an electron, and the electron is
ejected:
1
0
n11 p  10 e , which leads to
General Form:
A
Z
X 
Y  10 e (β-)
A
Z 1
Example (complete what’s missing):
6
C
14
N  10 e
In the second case, a proton converts to a neutron and a positron:
1
1
p 01 n 0 e , which leads to
General Form:
A
Z
X 
Y  10 e (β+)
A
Z 1
(c) Electron Capture and Gamma Ray Emission:
A nucleus may capture an electron, converting a proton to a neutron, but also exciting the nucleus to emit
high energy gamma rays:
General Form: (complete what’s missing): ZA X  10 e 
Y  00  (gamma rays)
```