PLEASE HELP 5TH GRADE SCIENCE! Charlotte completed an experiment in which she investigated and discovered that an electrically charged object can attract an uncharged object without any contact. She used a PVC pipe and small pieces of paper for her experiment. Each time, she rubbed the PVC pipe with a cloth to give it a charge and then held it over paper. What would be Charlotte's control group in this experiment?

A. Using the cloth and rubbing it against the PVC pipe
B. Taking the pieces of paper and rubbing it against the cloth
C. Not rubbing the cloth against the PVC pipe or the paper
D. Rubbing the cloth against both the paper and the PVC pipe

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. show that copm can be expressed in terms of the reservoir temperatures tc and th, the cold and hot thermal resistances rt, c and rt, h, and qin, as where rtot rt, c rt, h. also, show that the power input may be expressed as 1.39 a household refrigerator operates with cold- and hot-temperature reservoirs of tc 5 c and th 25 c, respectively. when new, the cold and hot side resistances are rc, n 0.05 k/w and rh, n 0.04 k/w, respectively. over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to rh, d 0.1 k/w. it is desired to have a refrigerator cooling rate of qin 750 w. using the results of problem 1.38, determine the modified coefficient of performance and the required power input w under (a) clean and (b) dusty coil conditions. internally reversible refrigerator qout qin w high-temperature reservoir low-temperature reservoir th th, i tc, i tc high-temperature side resistance low-temperature side resistance w qin th tc qinrtot tc qinrtot copm tc qinrtot th tc

Which of the choices below is one of the primary gases found in the atmosphere? a. helium b. carbon dioxide c. nitrogen d. argon

What is a carrier wave and how does it affect what you hear on the radio