In this animated object, learners examine how the way in which a rheostat is connected in series with other resistors causes current and voltage to change as the resistance is varied. A brief quiz completes the activity.
Charging Time Constants of an RC Circuit (Screencast)
In this animated object, students view an explanation of how current, voltage, and the charge on a capacitor of a series RC circuit change during five time constants. A short quiz completes the activity.
Learners observe how a blood drop in flight continually accelerates and increases in velocity over time. As the drop falls, resistance accumulates. The increase in stain diameter relative to distance of a typical 50 ml drop of blood is represented here. This activity has audio content.
Learners watch a brief video clip. They then follow step-by-step instructions on how to do a urine colony count and examine the criteria for determining if a colony count represents an infection. A brief quiz completes the object.
Stain Measurement & Calculating Angles of Impact (Screencast)
In this learning object the student will learn how to measure a stain and calculate angles of impact. Determining the angle of impact for bloodstains takes advantage of the trigonometric functions (Sine function).
A mathematical relationship exists between the width and length of an elliptical bloodstain which allows for the calculation of the angle of the impact for the original spherical drop of blood.
Given well formed stains we can accurately measure the width and length by simply dividing the stain along it’s major and minor axis. The opposite halves would be generally equal to each other which aids in establishing the impact angle.
This screencast shows how blood droplets are held together by a strong cohesive molecular force that produces surface tension in each drop and on the external force. Surface tension pulls the surface molecules of a liquid toward its interior, decreasing the surface area and causing the liquid to resist penetration.