Which of the following statements is true?

(a) magnetic fields are strongest in the middle of the magnet.
(b) a magnetic field can be created by running an electric current through a magnet.
(c) electricity flows from positively charged area to negatively charge areas.
(d) static electricity is a build up of free protons and neutrons.

If 1.63 times 10 negative 4 of helium dissolves in 100.0g of water, what is the concentration in parts per million

What material does not melt at any temperature

Tooth enamel consists mainly of the mineral calcium hydroxyapatite, ca_10(po_4)_6(oh)_2. trace elements in teeth of archaeological specimens provide anthropologist with clues about diet and diseases of ancient people. students at hamline university measured strontium in enamel from extracted wisdom teeth by atomic absorption spectroscopy. solutions with a constant total volume of 10.0 ml contained 0.726 mg of dissolved tooth enamel plus variable concentrations of added sr. added sr find the concentration of sr in the 10 ml sample solution in parts per billion = ng/ml. find the concentration of sr in tooth enamel in parts per million = mu g/g.