PhysicsChapter 6: Alternating Current
Rms and Peak Values
The RMS value
Definition
The RMS value of an alternating current or voltage is the effective value that produces the same average heating effect in a resistor as an equivalent DC value.
Why Ordinary Average Is Not Used
For sinusoidal current: Irms = I₀√2 For sinusoidal voltage: Vrms = V₀√2 Therefore: I₀=√2 Irms and: V₀=√2 Vrms Numerically: 1√2 ≈ 0.707 So: `Irms≈0.707I₀` `Vrms≈0.707V₀` Over one complete sinusoidal cycle, the signed average current is zero because positive and negative halves cancel. But AC can still produce heating. RMS gives a useful measure of this effective electrical value.
Formula / Key Relation
**Irms=I₀√2 Vrms=V₀√2**
Exam preparation
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Review the key facts, formulas and checks before you move on.Rms and Peak Values
Sticky Notes · Quick Revision
RMS
- `Iᵣₘₛ=I₀√2`
- `Vᵣₘₛ=V₀√2`
- ≈ 0.707 × peak
60-second revision
- RMS is the effective AC value based on heating effect.
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