Current - Questions 14 Help

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The current in an electric circuit flows from the positive (+) terminal of the battery pack through the light bulbs to the negative (-) terminal of the battery pack. The actual value is the same in every wire; it does NOT decrease after passing through a bulb. If there are more than one bulb and if the bulbs are identical, then they will be of equal brightness.

There are three similar versions of this question. Here is one of the versions:

Version 1:

The diagrams represent bulb brightness using starbursts and current using arrowtails. Give attention to the relative brightness of bulbs, to the relative current, and to the current direction. Select any diagrams that incorrectly convey a current concept.

Be an Inspector
You have a job to do! You have to inspect each circuit diagram, details included, to determine which diagram(s) violate a current concept. This means that you will need to know your concepts and that you will need to inspect the details of each arrowtail and each starburst to determine if they satisfy the laws of physics. If they don't, then tap on the diagram and put it behind bars as a law breaker.

Know Your Concepts
So what are the concepts? What do the laws of physics dictate about charge flow in circuits? There's at least three things to know:

1) Current is everywhere the same in an electric circuit. The current in the first bulb is the same as the current in the second bulb. The current in the first wire is the same as the current in the last wire.

2) Conventional current has a clearly-defined direction. It is directed from the positive (+) terminal of the battery pack through the external circuit and back to the negative (-) terminal of the battery pack.

3) When there are two or more identical bulbs in a circuit, the brightness of each bulb will be identical. The first bulb can be expected to be equally bright as the last bulb.

Here's Some Details
Arrowtails: The arrowtails are a representation used to indicate the relative amount of current in a circuit. The number of tails that trail behind the arrowhead is an indicator of the amount of current. If you view nine tails behind the arrowhead, then that is a representation of there being more current than if you viewed one tail behind the arrowhead. We would expect that the number of arrowtails would be the same for each wire within the same circuit.

Arrow Direction: The direction of the arrows represent the direction of the conventional current. We expect that this direction would be from the positive terminal of the battery pack around the loop and back to the negative terminal.

Starbursts: The rays that surround a bulb are called starbursts and communicate information about how bright the bulb is. A bright bulb will have a lot of rays around it. A dimmer bulb will have fewer rays around it. A correctly drawn diagram for a 2-bulb or a 3-bulb circuit would display the same number of rays around each bulb. That is, the bulbs would shine equally bright.

Try this link to The Physics Classroom Tutorial for more help with the concept of electric current:

Electric Current