A long solenoid (cylinder wrapped with many turns of wire) creates a magnetic field inside of it equal to B=µnI, where µ=4π*10^-7, m/A is the number of turns of wire per unit length, and I is the current in the wire. If the solenoid is very long, then outside (far from the ends) the field is zero.

a. Consider a solenoid with 100 turns of wire per cm (n=100cm^-1). If a current of 2A runs through it, what is the field inside?
b. Let the radius of the solenoid be R1= 2 cm, the radius of a small loop inside it be R2= 1 cm and the radius of a big loop outside it be R3= 5 cm. find the flux through the two loops.
c. Now suppose that the current is decreased at a constant rate from 2A to zero over a time of .2 seconds. What is the EMF induced in (around) each of the two loops (if there were breaks in them)?

Researchers conducted an experiment to identify the effects of three different hand sanitizers on the growth of bacteria. the researchers grew one type of bacteria in twenty-four identical covered petri dishes. then, they opened eighteen petri dishes and applied the three hand sanitizers to six petri dishes each. they left the remaining six petri dishes closed as a control group. when the researchers measured the growth of bacteria two days later, the six dishes that had no hand sanitizer showed the least amount of bacterial growth. the researchers concluded that not using any hand sanitizer would lead to the least bacterial growth. which statement best explains why the researchers’ conclusion was not justified? the experiment tested too many variables. the control group was not treated the same as the experimental group. the sample size of twenty-four petri dishes is not large enough. the single type of bacteria is not adequate to make any conclusions.