2 min read
Ac Through a Resistor
In a purely resistive AC circuit, current and voltage are in phase.
Choose Your Level
Ac Through a Resistor
What is it?
In a purely resistive AC circuit, current and voltage are in phase.
In simple words
- A pure resistor creates no phase difference.
Recommended for Class 12
Full school-level explanation
In a purely resistive AC circuit, current and voltage are in phase.
Power
Suppose: v=V₀sinωt From Ohm's law: i=vR Therefore: i=(V₀R)sinωt or: i=I₀sinωt where: I₀=V₀R Thus current and voltage reach: zero together; positive maximum together; negative maximum together. Therefore phase difference: φ=0 Using RMS values: Vrms=IrmsR Since V and I are in phase: Pavg=VrmsIrms and: Pavg=Irms²R*
Formula / Key Relation
**Vrms=IrmsR** **φ=0**
Remember
- Pavg=VrmsIrms
- Pavg=Irms²R
- Vrms=IrmsR
- φ=0
Deeper understanding
Go deeper on Ac Through a Resistor: connect the definition to reasons, relationships, exceptions, and exam wording.
Common mistakes
Exam focus
Pure R
Exam focus
Quick revision
- Pavg=VrmsIrms
- Pavg=Irms²R
- Vrms=IrmsR
- φ=0
- Power: Suppose: v=V₀sinωt From Ohm's law: i=vR Therefore: i=(V₀R)sinωt or: **i=I₀sinωt
- Formula / Key Relation: Vrms=IrmsR φ=0
For long answers on Ac Through a Resistor: define clearly → explain the main parts → give one example → state one exam caution.
Exam Focus
Exam Focus
Important points
- Pavg=VrmsIrms
- Pavg=Irms²R
- Vrms=IrmsR
- φ=0
Important formulas
- Pavg=VrmsIrms
- Pavg=Irms²R
- Vrms=IrmsR
Common exam traps
- Do not say current leads or lags voltage in a pure resistor.
- Do not say current leads or lags voltage in a pure resistor.
Long question structure
Definition → key parts → example → exam caution
Common Mistakes
Common Mistakes
- Mistake
Do not say current leads or lags voltage in a pure resistor.
- Mistake
Do not say current leads or lags voltage in a pure resistor.
- Mistake
Do not say current leads or lags voltage in a pure resistor.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
Pavg=VrmsIrms
Pavg=Irms²R
Vrms=IrmsR
φ=0
In a purely resistive AC circuit, current and voltage are in phase.
Pavg=VrmsIrms
- Definition
- In a purely resistive AC circuit, current and voltage are in phase.
- Formula
- Pavg=VrmsIrms
- Critical warning
- Do not say current leads or lags voltage in a pure resistor.
Did you understand this topic?
Your answer is saved with your learning record. It does not mark the topic as mastered.
Ready to test yourself?
You've completed the learning section.
Exam Practice
Define
Q1. Define Ac Through a Resistor.
Explain
Q2. Explain: Power.
Example
Q3. Give one clear example of Ac Through a Resistor and say why it fits.
Mistake
Q4. State one common mistake students make about Ac Through a Resistor.
Exam note
Q5. Write a short exam note on Ac Through a Resistor: definition, two points, one example.
Sources & References
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.