energy density

(noun)

The amount of energy that can be stored relative to the volume of the battery.

Related Terms

Examples of energy density in the following topics:

  • Energy in a Magnetic Field

    • The energy density is given as $u = \frac{\mathbf{B}\cdot\mathbf{B}}{2\mu}$.
    • For linear, non-dispersive, materials (such that B = μH where μ, called the permeability, is frequency-independent), the energy density is:
    • Energy density is the amount of energy stored in a given system or region of space per unit volume.
    • For linear non-dispersive materials, though, the general equation leads directly to the simpler energy density equation given above.
    • Express the energy density of a magnetic field in a form of equation

  • Energy Density

    • How much energy is in the box at any time?
    • First it is easiest to think about how much energy in the box is traveling in a particular direction through the box during a small time interval such that $c dt$ is the length of the box,
    • This energy equals the energy that enters the box traveling in the right direction during the time interval $dt$,
    • To get the total energy density you have to integrate over all of the ray directions

  • Problems

    • Let's suppose that the gas has a uniform density $\rho$ and consists of hydrogen with mass-fraction $X$ and helium with mass-fraction $Y$ and other stuff $Z$.You can assume that $Z/A=1/2$ is for the other stuff.What is the number density of electrons in the gas?
    • What is the synchrotron emission from a single electron passing through a magnetic field in terms of the energy density of the magnetic field and the Lorentz factor of the electron?
    • The number density of the electrons is $n_e$ and they fill aspherical region of radius $R$.What is the energy density of photons within the sphere, assuming that it is optically thin?
    • What is the inverse Compton emission from a single electron passing through a gas of photons field in terms of the energy density of the photons and the Lorentz factor of the electron?

  • The Hydrogen Economy

    • As such, hydrogen is not a primary energy source, but an energy carrier.
    • As a potential fuel, hydrogen is appealing because it has a high energy density by weight.
    • Fuel cells are electrochemical devices capable of transforming chemical energy into electrical energy.
    • Although H2 has high energy density based on mass, it has very low energy density based on volume.
    • Increasing the gas pressure will ultimately improve the energy density by volume, but this requires a greater amount of energy be expended to pressurize the gas.

  • Energy Stored in a Magnetic Field

    • Due to energy conservation, the energy needed to drive the original current must have an outlet.
    • The formula for this energy is given as:
    • From Eq. 1, the energy stored in the magnetic field created by the solenoid is:
    • Therefore, the energy density $u_B = energy / volume$ of a magnetic field B is written as $u_B = \frac{B^2}{2\mu}$.
    • Energy is "stored" in the magnetic field.

  • Female Athlete Triad: Disordered Eating, Amenorrhea, and Premature Osteoporosis

    • Female athlete triad is a combination of eating disorders, disrupted menstruation, and low bone density.
    • Female Athlete Triad is a syndrome in which eating disorders (or low energy availability), amenorrhoea/oligomenorrhoea, and decreased bone mineral density (osteoporosis and osteopenia) are present.
    • Energy is taken in through food consumption.
    • As osteoclasts break down bone, patients see a loss of bone mineral density.
    • Low bone mineral density renders bones more brittle and hence susceptible to fracture.

  • Problems

    • Calculate the energy and wavelength of the hyperfine transition of the hydrogen atom.
    • You may use the following formula for the energy of two magnets near to each other
    • Calculate the energy and wavelength of the transition of hydrogen with the spin of the electron and proton aligned to antialigned.
    • Calculate the ionized fraction of pure hydrogen as a function of the density for a fixed temperature.

  • Nuclear Size and Density

    • Nuclear size is defined by nuclear radius; nuclear density can be calculated from nuclear size.
    • It can be measured by the scattering of electrons by the nucleus and also inferred from the effects of finite nuclear size on electron energy levels as measured in atomic spectra.
    • Nuclear density is the density of the nucleus of an atom, averaging about $4 \cdot 10^{17} \text{kg/}\text{m}^3$.
    • The nuclear density for a typical nucleus can be approximately calculated from the size of the nucleus:

  • Supercritical Fluids

    • This can be rationalized by thinking that at high enough temperatures (above the critical temperature) the kinetic energy of the molecules is high enough to overcome any intermolecular forces that would condense the sample into the liquid phase.
    • Since density increases with pressure, solubility tends to increase with pressure.
    • At constant density, solubility will increase with temperature.
    • Other properties, such as density, can also be calculated using equations of state.
    • The system consists of 2 phases in equilibrium, a dense liquid and a low density gas.

  • Crystal Field Theory

    • Therefore, the d electrons closer to the ligands will have a higher energy than those further away, which results in the d orbitals splitting in energy.
    • All of the d orbitals have four lobes of electron density, except for the dz2 orbital, which has two opposing lobes and a doughnut of electron density around the middle.
    • On the other hand, the lobes of the dxy, dxz, and dyz all line up in the quadrants, with no electron density on the axes.
    • For example, in the case of an octahedron, the t2g set becomes lower in energy.
    • Conversely, the eg orbitals are higher in energy.