In this animated object, learners examine how a gateway server operates.

This animated lesson shows how pushing a start or stop button on a ladder circuit causes the cylinder of a hydraulic circuit to extend and retract.

This animated lesson shows how a pressure switch connected in a ladder circuit causes the cylinder of a hydraulic circuit to extend and retract.

This animated lesson shows the operation of timer-on and timer-off delay relays used in ladder circuit operate.

Learners read about the vector diagram for a parallel RL circuit. This animated lesson presents information on current flow through each branch, total current, and phase angle.

In this animated and interactive lesson, learners examine additive and subtractive color theories.

In this lesson on atomic structure, learners examine how the binding energy of electrons affects light production in certain phosphors used in x-rays.

Students match images of insects and other pests with their descriptions in this lesson on keeping a food service operation free from contamination.

This lesson provides a drawing with steps to complete the activity.

Students locate the enamel, cementum, cementoenamel junction, the anatomic crown, and the root of a tooth in this interactive lesson.

In this animated lesson, learners follow the steps required to read the phase shift difference in degrees between two AC waveforms.

In this interactive lesson, learners study examples of the expressions "a few" and "a little" with count and noncount nouns. They practice using these expressions in a drag-and-drop exercise of 20 sentences.

In this animated lesson, students read an analogy comparing water in a "special" water tank to the current "flow" through a capacitor.

Users examine ways for students to give feedback to their instructor about what they have learned and what part of the lesson is not clear.

Students read descriptions of the voltage, current, and turns ratios of the primary and secondary coils for a transformer in this interactive lesson.

At the end of this lesson you will be able to

- Explain what biosecurity means.

- Describe why biosecurity is important.

- Identify what kinds of disease agents we try to prevent or control with biosecurity.

- Demonstrate disease agent-host-environmental interactions that result in disease.

Learners assess the periodontal status and the health risk factors of a fictitious patient. They also make treatment recommendations in this interactive lesson.

This lesson provides a drawing with steps to complete the activity.

Learners read an explanation of variation and how it can make a process unpredictable. They distinguish between common and special causes of variation in a brief exercise at the end of the lesson.

In this animated activity, learners examine how the speed of a motor may change if the voltage from the power source fluctuates due to power line irregularities. This lesson has audio content.