Unit 1 Energy

Standard SI unit for measuring energy

Joule ($\text{J}$)

Formula for gravitational potential energy ($GPE$)

$$GPE = mgh$$

• $m$ = mass ($\text{kg}$)
• $g$ = acceleration due to gravity ($9.8\,\text{m/s}^2$)
• $h$ = height ($\text{m}$)

Formula for kinetic energy ($KE$)

$$KE = \frac{1}{2}mv^2$$

• $m$ = mass ($\text{kg}$)
• $v$ = velocity ($\text{m/s}$)

Difference between energy transfer and energy conversion

• Energy Transfer: Energy moves from one location or object to another while maintaining the same form.
• Energy Conversion: Energy changes from one type into another type.

Gravitational potential energy ($GPE$)

The energy stored in an object due to its position or height relative to the ground, which increases with greater mass and higher elevation.

Elastic potential energy

Energy stored in an object when it is temporarily deformed (such as being stretched or compressed) and has the ability to return to its original shape.

Chemical potential energy

Energy stored within the chemical bonds of molecules, which can be released during chemical reactions like combustion or digestion.

Nuclear fission vs. nuclear fusion

• Nuclear Fission: The splitting of a heavy atomic nucleus into smaller nuclei, releasing heat and radiation.
• Nuclear Fusion: The combining of light atomic nuclei to form a heavier nucleus (such as the reactions powering the Sun).

Thermal energy

The sum of the kinetic energies of all individual particles vibrating and moving within a substance.

Energy conversion path in a nuclear power plant

Nuclear energy $\rightarrow$ thermal energy (boiling water into steam) $\rightarrow$ kinetic energy of a spinning turbine $\rightarrow$ electrical energy via a generator.

How an electric generator converts kinetic energy into electricity

Magnets spin relative to copper wire coils; the fluctuating magnetic field exerts a force on electrons in the wire, inducing electrical current.

Primary form into which dissipated or "lost" energy converts

Thermal energy, which spreads out into the surrounding environment.

Pumped hydro energy storage

Excess electrical energy is used to pump water up to a high-elevation reservoir ($GPE$); when electricity is needed, water is released to spin a turbine and generator ($KE \rightarrow EE$).

Flywheel battery mechanism

Electrical energy powers a motor that accelerates a rotor on low-friction magnetic bearings to store energy as rotational kinetic energy; when power is needed, the slowing rotor acts as a generator to produce electricity.

Sand battery mechanism

Excess electricity heats air that circulates through insulated sand, storing energy as thermal energy until heat extraction pipes draw it back out for use.