Summary of "Resistors in Series and Parallel Circuits Experiment - GCSE Physics Required Practical"

Overview

This GCSE physics practical measures the resistance of two identical resistors:
- individually, connected in series, and connected in parallel.
Instruments used: low-voltage cells (max recommended 4 V), an ammeter, a voltmeter, connecting wires, and two covered-value resistors.
Main purpose: collect current (I) and potential difference (V) readings so resistance can be calculated and compared using R = V / I.

Two cells used (to keep supply ≤ 4 V).
Ammeter placed in series with the resistor(s) to measure current.
Voltmeter placed in parallel across the resistor or resistor combination to measure voltage.
Care taken to avoid wiring confusion when rearranging circuits.

Test circuit and first resistor
- Connect one resistor in series with the ammeter and the cells.
- Confirm circuit works by reading current on the ammeter (reported ≈ 0.26–0.27 A).
Measure voltage across single resistor
- Connect the voltmeter in parallel with that resistor.
- Record the potential difference (reported ≈ 2.68 V).
- Calculate the resistor’s value: R = V / I.
Repeat for the second resistor
- Replace the first resistor with the second (identical) resistor.
- Note the voltage fluctuated between about 2.4 V and 2.5 V — choose a value by judgement and record.
Series connection
- Remove the voltmeter to avoid confusion, connect the two resistors end-to-end (series) and reconnect the ammeter.
- Put the voltmeter in parallel across the series combination and record I and V for the combined resistance.
- Readings are used to compare total resistance in series.
Parallel connection
- Disconnect and rewire the two resistors so both ends are connected together (parallel).
- Take care with wire placement; connect voltmeter across the parallel group.
- Observe increased total current in the circuit (observed values: V across both ≈ 2.46 V; total current ≈ 0.47–0.48 A).
- Use these readings to calculate the combined resistance for the parallel arrangement.

Use V and I readings to calculate resistance via R = V / I.
Individual resistors gave a current around 0.26–0.27 A with ≈ 2.68 V across one resistor.
The second resistor showed slightly different (fluctuating) voltage readings — this highlights measurement uncertainty and the need for consistent readings/technique.
Series connection increases total resistance (reduces circuit current compared with parallel).
Parallel connection reduces total resistance (increases circuit current compared with series).

For identical resistors:

Series total resistance: R_total = R1 + R2 = 2R.
Parallel total resistance: R_total = (1/R1 + 1/R2)^(-1) = R/2 (equivalently, R_total = 1 / (1/R1 + 1/R2)).

Keep supply voltage within the recommended limit (max 4 V).
Double-check wiring when changing configurations to avoid errors.
Expect small fluctuations in meter readings — take several readings or note the range and use consistent judgement when recording.