Resistance and Ohm's Law
Part of the Electricity and Magnetism section of Coddy's Physics journey. Lesson 22 of 51.
Ohm's law: the current through a resistor is proportional to the voltage across it:
V = I R
with R in ohms (1 Ω = 1 V/A).
A wire's resistance:
R = ρ L / A
Longer: more resistance; thicker: less. ρ, the resistivity, belongs to the material.
Challenge
A copper wire is 10 m long with a cross-section of 1 mm² (1 × 10⁻⁶ m²). Copper's resistivity is 1.7 × 10⁻⁸ Ω·m. What current I flows when 1.7 V is put across the wire? Work out its resistance first.
Try it yourself
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Electricity and Magnetism
3Energy and Potential
Electric Potential EnergyElectric PotentialField and PotentialRecap - Accelerating Ions6Current and Resistance
Current and VoltageResistance and Ohm's LawSeries and ParallelElectric PowerRecap - Fairy Lights9Capacitors in Circuits
A Capacitor in a CircuitCharging a CapacitorDischarging a CapacitorRecap - Defibrillator