Answer:
a. longitudinal
Explanation:
A longitudinal study examines a given group over a long period of time, so collecting data from the same group of 30 people over their lifetime certainly fits that definition. It's more like an evolution study.
A cross-sectional compares different groups at the same point in time. So, it's more like a survey.
A microgenetic is much focused in time, providing multiple data sets in a short time to examine rapid evolution of a subject.
An experimental study design will make interactions and experiments with the study group, while this is not the case here apparently, and experimental is usually for a much shorter period than a generation.
Answer:
Compared to other AP® exams, AP® Psychology is considered one of the easier exams to pass in the AP® catalog for the reasons described below. In 2021, the AP® Psychology exam had a passing rate of 53.3% with a mean score of 2.71
Explanation:
DC motors are usually seen in applications where the motor speed needs to be externally controlled. AC motors work best in applications where power performance is sought for extended periods of time. All DC motors are single phase, but AC motors can be single phase or three phase.
AC and DC motors use the same principle of using an armature winding and magnetic field except with DC motors, the armature rotates while the magnetic field doesn’t rotate. In AC motors the armature does not rotate and the magnetic field continuously rotates.
In some applications today, DC electric motors are replaced by combining an AC electric motor with an electronic speed controller, known as variable frequency drives. DC electric motors are replaced with an AC electric motor and an electronic speed controller because it is a more economical and less expensive solution.
DC electric motors have many moving parts that are expensive to replace, and DC electric motor repair is usually more expensive than using a new AC electric motor with an electronic controller.
In our experience, combining an AC motor and drive proves to be the most cost effective solution for mostapplications. When servicing our customers in the field, we often recommend looking at the SMVector Series Variable Frequency Drive in combination with a three phase AC motor.
