Electricity
Learn electric charge, electric current, electric potential and potential difference, Ohm's law, resistance, factors affecting resistance, electric circuits, electrical energy, and electric power. Use the interactive simulator below to explore a simple DC circuit: adjust voltage V and resistance R to see current I = V/R and power P = VI. Use Launch to start the animation and Play / Pause to control it.
- Current β flow of charge (A)
- Voltage β potential difference (V)
- Resistance β opposition to flow (Ξ©)
- Power β energy rate (W)
Parameters
Try: Set V = 12 V, then double R. Watch I and P change.
Key formulas
Real-world applications
Household wiring
Mains at high voltage (e.g. 230 V); devices have fixed R, so current is set by V and R.
Key insight: Higher voltage allows lower current for the same power.
Appliances & power ratings
Ratings like 1000 W tell you power; P = VI shows how much current they draw.
Key insight: Power ratings determine current drawn at fixed voltage.
Batteries & energy use
Battery gives roughly constant V; the load sets I = V/R and how long it lasts.
Key insight: Constant V and load R set I; energy = VIt sets runtime.
How V, I and R interact
Voltage is the push that drives charge. Higher V β more push.
V slider β β current β
Resistance opposes flow. Higher R β less current for the same V.
R slider β β current β
Current is the result: I = V/R. Same current through the whole loop.
Live value I = V/R
Common misconceptions & tips
Current is not used up; the same current enters and leaves. Energy is converted to heat (P = IΒ²R).
π Charge is conserved; only energy is transformed.
π’ I same everywhere in series
π§ͺ In the simulator, notice current stays the same throughout the loop.
P = IΒ²R β so if R goes up and I drops a lot (e.g. in series), power can decrease.
π Heating depends on both I and R, not R alone.
π’ P = IΒ²R
π§ͺ Try increasing R in the sim and watch P.
Voltage is measured between two points (potential difference). Current is flow through a point.
π Potential difference requires two points; current is defined at a cross-section.
π’ V = potential difference
π§ͺ In the sim, V is across the battery (and resistor).
Tip: Use the sim: set V and R, then check that I = V/R and P = VI match the displayed values.
Chapter Guide
How to Study This Chapter
- Start with Electric Charge
- Build concepts: Current β Voltage β Resistance
- Connect ideas using Ohm's Law
- Apply concepts with Power & Energy simulations
What You'll Learn
- Explain how charge and current are related
- Apply Ohm's law in simple circuits
- Understand basic circuit behaviour
- Interpret power and energy usage
Subtopics β Electricity
Each subtopic has a dedicated page with clear explanations and an interactive simulator where relevant.
Electric Charge
Electric charge is a fundamental property of matter. Like charges repel, unlike charges attract. SI unit is the coulomb (C).
Read more βElectric Current
Electric current is the rate of flow of electric charge. I = Q/t. SI unit is the ampere (A).
Read more βElectric Potential and Potential Difference
Electric potential at a point is work done per unit charge to bring a test charge from infinity. Potential difference (voltage) is the difference in potential between two points.
Read more βOhm's Law
Ohm's law states that for many conductors, V = IR: the potential difference across a conductor is proportional to the current through it, at constant temperature.
Read more βResistance
Resistance is the opposition offered by a conductor to the flow of current. R = V/I. Unit is the ohm (Ξ©).
Read more βFactors Affecting Resistance
Resistance of a conductor depends on its length, cross-sectional area, and material: R = Ο L/A, where Ο is resistivity.
Read more βElectric Circuit
An electric circuit is a closed path in which current can flow. It typically includes a source (e.g. battery), conductors, and loads (e.g. resistors, lamps).
Read more βElectrical Energy
Electrical energy consumed when charge Q moves through a potential difference V is E = VQ = VIt. Unit is the joule (J).
Read more βElectric Power
Electric power is the rate at which electrical energy is consumed or supplied. P = VI = IΒ²R = VΒ²/R. Unit is the watt (W).
Read more βElectric Motor
Understand how electric current produces rotational motion using magnetic fields.
Read more β