AP Physics 2: Algebra-Based Flashcards: Resistance, Resistivity, and Ohm's Law
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 14 cards to help you master important concepts.
State the equation for Ohm's Law.
Ohm's Law is expressed by the equation $I=\frac{\Delta V}{R}$.
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State the equation for Ohm's Law.
Ohm's Law is expressed by the equation $I=\frac{\Delta V}{R}$.
If you want to create a resistor with high resistance, what properties should the material and its shape have?
To create a high-resistance resistor, you should use a material with high resistivity, make it very long, and give it a small cross-sectional area.
Distinguish between resistance and resistivity.
Resistivity is an intrinsic property of a material, while resistance is a property of a specific object that depends on its material (resistivity) and its geometry (length and area).
What is resistivity?
Resistivity is a fundamental property of a material that quantifies how strongly it opposes the motion of electric charge, based on its atomic and molecular structure.
What is electrical resistance?
Resistance is a measure of the degree to which an object opposes the movement of electric charge.
State the relationship between resistance, resistivity, length, and cross-sectional area.
The resistance of a resistor is directly proportional to its resistivity and length, and inversely proportional to its cross-sectional area.
What relationship does Ohm's law describe?
Ohm's law relates the current (I), potential difference (ΔV), and resistance (R) across a conductive element of a circuit.
Which physical properties of an object determine its resistance?
An object's resistance is determined by its material's resistivity, its length, and its cross-sectional area.
If the length of a wire is doubled while its other properties remain constant, how does its resistance change?
The resistance will double, because resistance is directly proportional to length ($R \propto l$).
Two wires are made of the same material and have the same length. Wire A is thicker than Wire B. Which wire has less resistance?
Wire A has less resistance because it has a larger cross-sectional area, which provides more pathways for the charge to move.
What is the formula for calculating the resistance of a resistor with uniform geometry?
The formula is $R= rac{\rho l}{A}$, where R is resistance, ρ is resistivity, l is length, and A is cross-sectional area.
If the cross-sectional area of a wire is doubled while its other properties remain constant, how does its resistance change?
The resistance will be halved, because resistance is inversely proportional to cross-sectional area ($R \propto 1/A$).
What are ohmic materials?
Ohmic materials are materials that obey Ohm's law, meaning they have a constant resistance for all currents.
According to Ohm's law, what happens to the current through an ohmic resistor if the potential difference across it is tripled?
The current will also be tripled, as current is directly proportional to the potential difference for an ohmic material.