Investigating factors that affect resistance
Instructions and answers for teachers
These instructions should accompany the OCR resource ‘Investigating factors that affect resistance’
Student Task Sheet which supports GCSE (9–1) Gateway Physics A
The Activity:
This resource comprises of 1 task.
Associated materials:
Physics A Investigating factors that affect resistance Lesson Element learner activity sheet.
This activity offers an
opportunity for English
skills development.
This resource is an exemplar of the types of materials that will be provided to assist in the teaching of the new
qualifications being developed for first teaching in 2016. It can be used to teach existing qualifications but may
be updated in the future to reflect changes in the new qualifications. Please check the OCR website for updates
and additional resources being released. We would welcome your feedback so please get in touch.
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Introduction
These practical tasks help students to plot a graph to see the relationship between wire length and
resistance, wire thickness and resistance and material and resistance.
Misconceptions
Students often visualise charge moving through a piece of wire like cards travelling down a road, or
water moving through a pipe. When we introduce the idea of charge passing through a thin piece of wire
students immediately think that it slows down, like a bottle-neck in a traffic jam.
Similarly, students think that thicker wires have less resistance because the charges have more space.
This usually stems from the false idea that charge travels down an empty wire: like a pipe.
By plotting a graph students can see how the relationship may not be as expected (based on the above
misconceptions).
Notes for teachers
Learning outcomes:
•
Recall that current (I) depends on both resistance (R) and potential difference (V) and the units in
which these are measured
•
Use the calculation resistance = potential difference/current
•
Use graphs and relate the curves produced to the function and properties of circuit elements
•
Scientific inquiry: make predictions based on prior knowledge, and test these predictions via a
practical investigation
•
Scientific inquiry: collect data and plot a graph of results for each investigation
•
Draw conclusions from data collected
•
Describe the effect of wire length, wire thickness and material of wire on resistance.
Running the activity
Full instructions are on the student sheets.
It is advised the investigations are carried out prior to the class practical to ensure materials do not
overheat. A 9V power source has been advised yet this may need to be reduced for safety.
As well as the students investigating all three factors affecting resistance you may wish to split the group,
have a number investigating each one and then share results if time is limited.
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Scientific inquiry may be worked on here via the following extra tasks:
•
•
•
•
•
Asking students to identify the independent, dependent, and control variables
Write a hypothesis
Highlight any errors that may occur
Possible solutions to errors i.e. how may a data logger change results/findings
How can you improve the reliability of these investigations?
Extension questions:
1. Nichrome is used in the heating elements of electric fires. Suggest why nichrome is used instead
of copper.
2. Suggest why fuses are made of thin pieces of wire.
3. Research what a circuit breaker is. Why could this be better than a fuse?
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Supporting information
Laptops are needed if students reach the extension Q3. The following web pages are useful.
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/electricityworld/mainselectricityrev
3.shtml
http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electricity/householdelecrev4.shtml
http://www.gcsescience.com/pme8.htm
http://www.cyberphysics.co.uk/topics/electricity/home/circuit_breaker.htm
Possible answers to extension Q3:
Circuit breakers act quicker, more reliable, it can be re-set, some types are so sensitive they can stop
you being electrocuted (RCCB circuit breakers).
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