Ohm’s Law and Simple Circuits Study Pack

Kibin's free study pack on Ohm’s Law and Simple Circuits includes a 3-section study guide, 8 quiz questions, 10 flashcards, and 1 open-ended Explain review question. Sign up free to track your progress toward mastery, plus upload your own notes and recordings to create personalized study packs organized by course.

Last updated May 21, 2026

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Ohm’s Law and Simple Circuits Study Guide

Master the core relationships that govern electric circuits, from applying I = V/R to ohmic materials to calculating total resistance in series and parallel configurations. This pack covers resistivity, the reciprocal formula for parallel branches, all three forms of the power equation, and why non-ohmic devices like diodes fall outside Ohm's Law — everything you need to tackle College Physics circuit problems confidently.

Key Takeaways

  • •Ohm's Law states that the current through a conductor equals the voltage across it divided by its resistance (I = V/R), and applies only to ohmic materials where resistance stays constant regardless of voltage.
  • •Resistance is an intrinsic property of a material determined by its resistivity, length, and cross-sectional area; longer and thinner conductors have higher resistance.
  • •In a series circuit, resistors share the same current and their resistances add directly, so total resistance equals the sum of all individual resistances.
  • •In a parallel circuit, resistors share the same voltage but split the current; total resistance is found using the reciprocal formula, and adding more parallel branches always decreases total resistance.
  • •Electric power dissipated by a resistor can be calculated as P = IV, P = I²R, or P = V²/R, depending on which quantities are known.
  • •Non-ohmic devices such as diodes and transistors do not maintain a constant resistance, so Ohm's Law cannot be applied to them directly.

Voltage, Current, and the Core Relationship

To understand circuits, you must first be clear on what voltage and current actually are and how they relate to each other through a conductor.

Electric Potential Difference (Voltage)

  • •Voltage, measured in volts (V), represents the difference in electric potential energy per unit charge between two points in a circuit.
  • •A battery or power supply creates this difference by doing work on charges, establishing a high-potential terminal and a low-potential terminal.
  • •Voltage is the 'push' that drives charges through a circuit; without a potential difference, there is no net flow of charge.

Electric Current

  • •Current, measured in amperes (A), is the rate at which positive charge flows past a given point in a circuit (I = ΔQ/Δt).
  • •By convention, current flows from the positive terminal of a source through the external circuit to the negative terminal, even though electrons physically move in the opposite direction.

Ohm's Law: I = V/R

  • •Ohm's Law states that the current I through a conductor is directly proportional to the voltage V across it and inversely proportional to its resistance R.
  • •The relationship is written I = V/R, or equivalently V = IR and R = V/I.
  • •This law was established experimentally by Georg Simon Ohm in the early 19th century and holds precisely only for ohmic materials under constant temperature conditions.

Resistance and Resistivity

Resistance quantifies how strongly a material opposes the flow of electric current, and it depends on both the material's intrinsic properties and its physical geometry.

What Resistance Measures

  • •Resistance, measured in ohms (Ω), arises because moving electrons collide with the lattice of atoms inside a conductor, losing kinetic energy as heat.
  • •Higher resistance means less current flows for a given voltage; lower resistance allows more current to flow.

Resistivity and Geometry

  • •The resistance of a uniform conductor is given by R = ρL/A, where ρ (rho) is the resistivity of the material in ohm-meters, L is the conductor's length, and A is its cross-sectional area.
  • •Doubling the length doubles the resistance because charges must travel through twice as many collision-producing atoms.
  • •Doubling the cross-sectional area halves the resistance because more parallel paths are available for charge flow.
  • •Resistivity is a material-specific constant: copper has a very low resistivity (~1.7 × 10⁻⁸ Ω·m), making it an excellent conductor, while rubber has an extremely high resistivity, making it an effective insulator.

Ohmic vs. Non-Ohmic Materials

  • •An ohmic material maintains a constant resistance regardless of the applied voltage, producing a perfectly linear current-versus-voltage graph.
  • •Non-ohmic devices such as diodes, light-emitting diodes (LEDs), and transistors have resistance that changes with voltage or current, so Ohm's Law cannot be directly applied to characterize their behavior.
  • •Temperature affects resistivity: for most metals, resistivity increases with temperature because thermal agitation creates more frequent electron collisions.

About this Study Pack

Created by Kibin to help students review key concepts, prepare for exams, and study more effectively. This Study Pack was checked for accuracy and curriculum alignment using authoritative educational sources. See sources below.

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