Resistors in series and in parallel
Measure two resistors separately, then joined in series and in parallel, and compare with the formulas.
Objectives
- Find resistance from ammeter and voltmeter readings.
- Verify the series and parallel combination rules.
Theory
Resistance is R = V/I. In series the same current flows through both resistors and the resistances add: Rs = R₁ + R₂. In parallel the potential difference is the same across both and 1/Rp = 1/R₁ + 1/R₂, so the combined resistance is smaller than either one.
Rs = R₁ + R₂ 1/Rp = 1/R₁ + 1/R₂
Procedure
- Measure current and voltage for resistor X alone.
- Measure resistor Y alone.
- Measure X and Y in series.
- Measure X and Y in parallel.
Precautions
- Keep the current below 1 A.
- Take each reading quickly to avoid heating.
- Subject
- Physics
- Grade
- 10–11
- Chapter
- Current Electricity (Nepal National Curriculum (CDC), grade 10)
- Difficulty
- Medium
- Duration
- 20 min
- Safety level
- Low
- Version
- 1.0
Apparatus
- Cells
- Rheostat
- Resistor
- Digital ammeter (0–1 A)
- Digital voltmeter (0–10 V)
- Key
- Connecting wires
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