05.3 - Electric Cells

Understandings:

• Cells

• Internal resistance

• Secondary cells

• Terminal potential difference

• Electromotive force (emf)

Applications and skills:

• Investigating practical electric cells (both primary and secondary)

• Describing the discharge characteristic of a simple cell (variation of terminal potential difference with time)

• Identifying the direction of current flow required to recharge a cell

• Determining internal resistance experimentally

• Solving problems involving emf, internal resistance and other electrical quantities

Guidance:

• Students should recognize that the terminal potential difference of a typical practical electric cell loses its initial value quickly, has a stable and constant value for most of its lifetime, followed by a rapid decrease to zero as the cell discharges completely

Data booklet reference:

• ε=I(R+r)

International-mindedness:

• Battery storage is important to society for use in areas such as portable devices, transportation options and back-up power supplies for medical facilities

Theory of knowledge:

• Battery storage is seen as useful to society despite the potential environmental issues surrounding their disposal. Should scientists be held morally responsible for the long-term consequences of their inventions and discoveries?

Utilization:

• The chemistry of electric cells (see Chemistry sub-topics 9.2 and C.6)

Aims:

• Aim 6: experiments could include (but are not limited to): investigation of simple electrolytic cells using various materials for the cathode, anode and electrolyte; software-based investigations of electrical cell design; comparison of the life expectancy of various batteries

• Aim 8: although cell technology can supply electricity without direct contribution from national grid systems (and the inherent carbon output issues), safe disposal of batteries and the chemicals they use can introduce land and water pollution problems

• Aim 10: improvements in cell technology have been through collaboration with chemists