Unit Overview
Practical circuits (AS)
CIE A-Level PhysicsΒ· 5 min read π n/a
1. Unit at a glance
This unit builds on your prior understanding of potential dividers and circuit rules to develop applied skills for practical physics work, which are regularly tested in AS written papers and required for your practical assessment. We progress from core practical potential divider designs, through integrating physical sensors into these circuits, to the critical process of calibrating measurement meters.
All topics in this unit connect theory to real experimental practice, so you will learn to recognize and solve common practical circuit problems that appear in CIE 9702 exam questions.
This unit includes 3 core sub-topics:
Practical potential divider circuits
Learn to design and analyze working variable potential divider circuits for adjustable voltage output.
β β β± 10 min
Sensors
Understand how to integrate common physical sensors into potential divider circuits for measurement.
β β β β± 12 min
Meter calibration
Learn the standard process for calibrating measurement meters to reduce systematic error.
β β β β± 10 min
2. Common Pitfalls
Wrong move:
Ignoring the loading effect of connected meters on potential divider output
Why:
Low-resistance meters change the total circuit resistance, leading to incorrect output voltage calculations
Correct move:
Always account for the parallel resistance of the connected measuring device when calculating output
Wrong move:
Mixing up resistance trends for common sensors
Why:
Confusing LDR or thermistor behavior leads to wrong predictions of output voltage change
Correct move:
Remember: NTC thermistors decrease resistance as temperature increases; LDRs decrease resistance as light intensity increases
Wrong move:
Skipping method steps when describing meter calibration in exams
Why:
CIE examiners award marks for complete, ordered method descriptions, not just outcomes
Correct move:
Always include zeroing, comparison to reference values, and correction of readings in your description
3. Quick Reference Cheatsheet
Concept / Rule | Key Information |
|---|---|
Practical potential divider output | (adjust for variable output) |
NTC Thermistor | Resistance as temperature |
LDR | Resistance as light intensity |
Sensor potential divider output | changes proportional to change in sensor resistance |
Loading effect | Low-resistance connected meters alter total circuit resistance and measured output |
Meter calibration | Compare unknown meter readings to accurate reference values to correct for systematic error |
What's Next
Begin this unit by learning core practical potential divider circuit designs. Work through all three sub-topics in order to build up your applied practical circuit knowledge, then move on to the next unit covering alternating current fundamentals.