12.3: Electrical Energy
pg. 511
Key Concepts:
1. Electrical energy is produced by energy transformations.
2. Electrical energy is produced from renewable and non-renewable
resources.
Electrical Energy: the energy provided by the flow of electrons in an
electric circuit.
- What makes it possible for all electrical devices to function?
- The energy sources provide electrons and enables electrons to flow through
the electric circuit.
- Electrical energy is measured in joules (J).
- Electrical energy is used to do work. This occurs when energy is
transformed into other forms of energy. (light energy, mechanical energy,
heat energy)
- Lightning is natural energy, but it can not be harnessed or used as a source
of usable energy.
Sources of Electrical Energy
- Electrical energy is used everyday, charging the battery in your cell phone,
turning on the lights, or toasting bread.
- The two main sources of electrical energy are batteries or electrical
generating stations.
- Batteries can only supply small amounts of energy over short periods of
time.
- Electrical generating stations supply a large continuous supply of electrical
energy.
Electric Cells
Electric Cell: a device that converts chemical energy into electrical energy.
Primary Cell: am electric cell that may only be used once.
Secondary Cell: an electric cell that can be recharged.
- An electrical cell (battery: two or more cells in combination) is a portable
device that converts chemical energy into electrical energy.
- Components of an electrical cell are: two electrodes, and a conducting
solution (electrolyte).
- There are a positive and a negative electrode, electrons flow from the
negative electrode to the positive electrode once conducted in a circuit.
- The electrolytes are repelled by the negative electrode and attracted to the
positive electrode.
- Primary cells are batteries that can not be recharged. The chemical
reactions can not be reversed. (Zinc chloride, alkaline, and lithium cells)
- Secondary Cells are batteries that can be recharged and reused. The
electrical energy from the outlet is used to reverse the chemical reactions.
Lead acid batteries (cars), and Nickel hydribe (NiMH) are examples.
- Most of these chemicals are toxic to the environment. Must be properly
recycled.
Figure 2: a) An electric cell contains an electrolyte that provides a source of
electrons. When the two electrodes of the cell are joined to the conducting
wires of a circuit, electrons flow from the negative electrode through the
circuit to the positive electrode. b) A 9 V battery consists of six 1.5 V
electric cells. The types of electrodes used and the chemicals in the
electrolyte affect how strong the flow of charge in an electric cell will be and
how long that flow will last.
Fuel Cells
- The fuel cells is a special type of electrical cell.
- A continuous supply of chemicals is pumped into the cell and wastes are
removed.
- A hydrogen fuel cell converts hydrogen gas and oxygen gas into water
while producing electrical energy.
- Fuel cell vehicles (FCVs) are vehicles use electric motors, fueled by fuel
cells.
- There are no harmful emissions from these vehicles.
- This type fuel cells is not necessarily harmless. The hydrogen gas comes
from fossil fuels.
- Pollution is created when fossil fuels are used to make hydrogen gas. This
contributes to greenhouse gas emissions and climate change.
Evidence of Learning …. Students can
- define electrical energy.
- explain how electrical energy is used to power common devices.
- describe the difference between different kinds of electric cells.
- identify different forms of electrical energy.
Check Your Learning:
Questions 1 – 8, page 514
Summary:
- Electrical energy is the energy provided by the flow of electrons in a
circuit. Electrical energy is measured in joules.
- Electrical cells produce small quantities of electrical energy and are useful
for portable electrical devices. Electric generating stations provide large
amounts of electrical energy.
- Primary cells cannot be recharged. Disposable batteries are an example of
primary cells.
- Secondary cells can be recharged and reused many times before being
recycled.
- Fuel cells require a continuous supply of fuel, such as hydrogen and
oxygen, to provide electrical energy.