Here’s the hypothesis for the duckweed experiemt

The controlled variables in an experiment are the ones that are kept the same for all trial runs, to ensure that no other factor except for the independent variable is being changed. In this case, the controlled variables are:

Timing of experiment: The timing of the experiment can be used as a controlled variable as a particular time constraint can be used to perform an experiment.

Duckweed population: The duckweed population should be kept as a constant to observe the impact of variables on the duckweed populations.

Environmental light: A particular environment light can be used as a standard under the influence of which the duckweed population shows growth.

Environmental temperature: A controlled standard temperature can be chosen for every trial to observe the growth of the duckweed.

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation:

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6