Current and potential difference ladders

What the Activity is for

Getting a feel for relative values of quantities.

Here you can impart an idea of the relative values of different currents and potential differences. Having an idea of these values for different sources and processes allows the units ampere and volt to acquire meaning, and enables the values derived from calculations to be checked against an internal model of what is reasonable. The ladders are one–dimensional graphs, used often to support quantification, putting the value of any physical quantity into a context.

What to Prepare

• appropriate scale prints of the support sheets provided
• cut out values and items from the support sheets (see below), if these are to be used
• some Blu–tack

What Happens During this Activity

The support sheets are provided in several formats so that you can use them in a number of ways.

You could provide a blank ladder at a large scale on the laboratory wall, and add values to it over the duration of the topic as you encounter these values.

You could provide a completed ladder, adding your own values to it as these come up in the conversations in the class. These could be stimulated by distributing a range of research questions to groups within the class to populate the values.

You could provide a blank ladder to a group, together with at least the objects and processes provided, and ask them to agree on how to place these items. Groups might then usefully compare their placements before being given the matching values, and so reordering their values, or you might provide the unmatched values and objects/processes, only placing them on the ladder afterwards.

Placing about five items on such a ladder produces a manageable demand.