A60-gallon water heater is initially filled with water at 66°f. determine how much energy, in btu, needs to be transferred to the water to raise its temperature to 104°f. given: the water properties at an average water temperature of 85ºf rho = 62.17 lbm/ft3 and cp = 0.999 btu/lbm-r.

18930 Btu

Explanation:

The amount of heat needed to raise the temperature of a body of water is given by:

Q = m * cp * (tfin - ti)

The mass is the volume multiplied by the density

m = V * ρ

So

Q = V * ρ * cp * (tfin - ti)

The volume of water is 60 gallon, which is equivalent to 8.021 ft^3

Now:

Q = 8.021 ft^3 * 62.17 lbm/(ft^3) * 0.999 Btu/(lbm * R)* (104 R - 66 R) = 18930 Btu

Since we have a temperature difference we can convert Fahrenheit to Rankine

absorption lines are where light has been absorbed by the atom thus you see a dip in the spectrum whereas.

emission spectra have spikes in the spectra due to atoms releasing photons at those wavelengths.

explanation:

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia