David decides to build an electromagnet to pick up the box of tacks he dropped on the floor. He did everything just like his teacher did in class with a D-cell battery, wire and nail But since he did not have any iron nails, he used a plastic nail from his baby brother's toy workbench to wrap the wire around. Which of
the following explains what happened when David hooked up the wire to the battery.
the electromagnet worked better when he hooked up a 9 von battery to replace the battery
the electromagnet did not work because the plastic nail acted as an insulator
the electromagnet did not work because the plastic nail allowed fewer cols in the electromagnet.
the electromagnet worked perfectly picking up all the tacks David dropped.

Distinguish between a transverse wave and a longitudinal wave.

Comedians like to joke that the reason we haven’t been visited by intelligent life from elsewhere in the universe is that aliens have been monitoring earth’s broadcasts of intellectually embarrassing tv programs, like gilligan’s island, fear factor, the jersey shore, and the jerry springer showand so consider us far too primitive to merit a visit. let’s check the assertion that aliens could have been receiving them. tv programs are broadcast at a frequency of about 100mhz with about 100kw of total power in 30frames per second, which emanatesroughly uniformly in all directions. assume that interstellar space transmits these broadcasts without attenuation. no matter how smart they are, aliens would require at least one photon per frame to interpret our signals. findthe number of photons per unit time per unit area reaching a receiver on a possible planet in the nearest star system, which is about 4 light-years away (a light-year is the distance light travels in a year). if aliens aimed a receiver or detector directly at earth, how big (in diameter) would it have to be to receive a photon per frame

What sort of waves exhibit the doppler effect?