In this circuit what happens to the relative brightness of the light bulbs before and after bulb-A burns out?

Two groups were taught the same material in the same time but using a conventional algebra-based approach or LEDs for electricity (AVOW diagrams).

Conventional solution

The best solution by a student taught with an algebra-based approach. The student got the right answer but some details of his explanation were wrong.

After 100 minutes of instruction on electricity, most students still got the wrong answer to this question.

AVOW solution

A typical correct solution &emdash; redrawn for clarity. Such answers are common for students taught with LEDs for electricity.

What is the resistance of this circuit of identical light bulbs?

This is a challenging "transfer" problem used as part of the post-test in one of our studies. It requires a sophisticated approach and conceptual understanding to solve.

Conventional solution

An incomplete solution typical of students taught with an algebra-based approach. Even the best students usually gained a fragmented understanding and fragile problem solving skills.

AVOW solution

A typical correct solution &emdash; common for students taught with LEDs for electricity. Students using LEDs usually acquire a good conceptual understanding and effective problem solving procedures.