Maths in physics and engineering · Accessible · Dissertation or artefact

Exponential charging in circuits: a maths EPQ idea

Why it works as an EPQ

A school-lab experiment tests an exponential model you can derive.

Scope and difficulty

Accessible. Accessible. One circuit, several resistor values, careful data.

The maths

Builds on these A Level topics: Exponentials and logarithms · Differentiation.

You would learn:

• First-order differential equations
• Time constants
• Fitting with logarithms

Learning maths beyond the course is expected in a maths EPQ, but you must understand and explain everything you use.

One possible plan

1. Derive the charging equation.
2. Measure voltage against time for several resistors.
3. Estimate time constants from linearised graphs.
4. Judge the fit and explain the differences.

Pitfalls

• Electrical safety: low-voltage kits only, with supervision.
• Not recording uncertainty.

Where to start reading

• Search for: RC circuit charging derivation
• Your physics department's capacitor practical

Prefer books, lecture notes, journal articles and official data to a single website, and record every source as you read (how to reference).

Making something? Read the artefact guide first: an artefact still needs a research-based written report.

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All maths in physics and engineering ideas · all 93 ideas

Your EPQ must be your own work. These pages coach: ideas, structure, checklists and planning. Submitting text, proofs, code or analysis written by someone else or by an AI tool as your own is malpractice. How to use help and AI honestly.