5.3. Electric Cells
You will be familiar with the standard AA battery (although they are becoming redundant in the age of modern rechargables). In Physics we often like to be very specific with our use of language – so Physicists would call this ‘a POWER CELL’ (or just ‘a cell’). When I connect multiple cells together, this is called a ‘battery’ (so 2 AA cells make a battery). Confused? To be honest, most Physicists aren’t that picky, but technically they have different circuit symbols, so it’s worth learning the difference.
So how exactly do batteries work? TedEd have a nice little introductory video which gives a nice little overview into how batteries work (for the IB you don’t need to worry about any of the chemistry of the internal reactions)
In this section we will look in a little more depth at power sources within circuits. The tricky part to get your head around is the idea of Internal Resistance and tackling some of the tricky MCQs that the IB sometimes ask.
The section is split up as follows
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Types of Cells - what is the difference between primary and secondary cells?
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Electromotive Force - the driving 'force' pushing electrical charge around a circuit
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Internal Resistance - the inherent resistance within a power supply
Types of Cells
There are hundreds of different types of power cell, all relying on different chemical processes for their function. In Physics, we don’t really care a huge amount about the different chemistries of these cells. We can largely group these into two categories – primary and secondary cells.
Video Lessons
Chris Doner | Cells, EMF and IR | IB Specific |
Resources
IB Physics | Topic 5 Notes | |||||
IB-Physics.net | Chapter 5 Summary | IB Revision Notes | ||||
Mr. G | 5.3 Teaching Notes | 5.3 Student Notes | ||||
Physics and Maths Tutor | Electricity Definitions | Electricity Key Points | Electricity Detailed Notes | Electricity Flashcards | A Level Resources - content slightly different |
Questions
Cambridge University Press | Topic 5: Add Qs | Topic 5: Add Qs MS | Topic 5: MCQs | CUP Website Link | Freely available online | |
Grade Gorilla | 5.2/3 (Circuits/ Cells) MCQ | Topic 5 (Circuits) End Quiz | Quick IB Specific Mixed MCQs | |||
Mr. G | 5.3 Formative Assessment | Topic 5 Summary Qs | IB Specific Questions |
Electromotive Force
A cell is a power supply for a circuit, providing electrical energy to the charge carriers as they move around the circuit. The energy each Coulomb of charge is given (i.e. the Voltage given) is termed the Electromotive Force (EMF).
Video Lessons
Chris Doner | Cells, EMF and IR | IB Specific | ||||
Gradepod | Electromotive Force | IB Specific | ||||
Physics Online | P.D. vs. EMF | Practical Tips | ||||
Science Shorts | EMF and Internal Resistance | Practical Tips | ||||
Study Nova | Internal Resistance |
Resources
IB Physics | Topic 5 Notes | |||||
IB-Physics.net | Chapter 5 Summary | IB Revision Notes | ||||
Mr. G | 5.3 Teaching Notes | 5.3 Student Notes | ||||
Physics and Maths Tutor | Electricity Definitions | Electricity Key Points | Electricity Detailed Notes | Electricity Flashcards | A Level Resources - content slightly different |
Questions
Cambridge University Press | Topic 5: Add Qs | Topic 5: Add Qs MS | Topic 5: MCQs | CUP Website Link | Freely available online | |
Grade Gorilla | 5.2/3 (Circuits/ Cells) MCQ | Topic 5 (Circuits) End Quiz | Quick IB Specific Mixed MCQs | |||
Mr. G | 5.3 Formative Assessment | Topic 5 Summary Qs | IB Specific Questions | |||
Physics and Maths Tutor | Internal Resistance (Edexcel 1) | Internal Resistance MS (Edexcel 1) | A-Level Qs: overlapping content | |||
Physics and Maths Tutor | Internal Resisistance (AQA 1) | Internal Resisistance MS (AQA 1) | EMF & IR (AQA 2) | EMF & IR MS (AQA 2) | A-Level Qs: overlapping content |
Internal Resistance
There is a common classroom experiment which allows you to calculate the internal resistance and EMF of a power source. It’s worth making sure you are confident with this experiment (the experimental setup and what the results show) as it is pretty commonly referenced. It is described in the following video.
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Video Lessons
Chris Doner | Cells, EMF and IR | IB Specific | ||||
Physics Online | Internal Resistance | Practical Tips | ||||
Science Shorts | EMF and Internal Resistance | Practical Tips | ||||
Study Nova | Internal Resistance |
Resources
IB Physics | Topic 5 Notes | |||||
IB-Physics.net | Chapter 5 Summary | IB Revision Notes | ||||
Mr. G | 5.3 Teaching Notes | 5.3 Student Notes | ||||
Physics and Maths Tutor | Electricity Definitions | Electricity Key Points | Electricity Detailed Notes | Electricity Flashcards | A Level Resources - content slightly different |
Questions
Cambridge University Press | Topic 5: Add Qs | Topic 5: Add Qs MS | Topic 5: MCQs | CUP Website Link | Freely available online | |
Dr French's Eclecticon | Electrical Circuits | Electrical Circuits Solutions | Link to Dr French's Site | Extension: Pre-University Material | ||
Grade Gorilla | 5.2/3 (Circuits/ Cells) MCQ | Topic 5 (Circuits) End Quiz | Quick IB Specific Mixed MCQs | |||
Isaac Physics | Internal Resistance | |||||
Mr. G | 5.3 Formative Assessment | Topic 5 Summary Qs | IB Specific Questions | |||
Physics and Maths Tutor | Internal Resisistance (AQA 1) | Internal Resisistance MS (AQA 1) | EMF & IR (AQA 2) | EMF & IR MS (AQA 2) | A-Level Qs: overlapping content | |
Physics and Maths Tutor | Internal Resistance (Edexcel 1) | Internal Resistance MS (Edexcel 1) | A-Level Qs: overlapping content |
Additional Resources
IB Questions
A question by question breakdown of the IB papers by year is shown below to allow you to filter questions by topic. Hopefully you have access to many of these papers through your school system. If available, there may be some links to online sources of questions, though please be patient if the links are broken! (DrR: If you do find some broken links, please contact me through the site)
Questions on this topic (Section 5) are shown in pale green.
Use this grid to practice past IB questions topic by topic. You can see from the colours how similar the question topic breakdown is year by year. The more you can familiarise yourself with the IB question style the better - eventually you will come to spot those tricks and types of questions that reappear each year.