MCAT Chemical and Physical Foundations of Biological Systems Flashcards: 4c Circuit Elements Ohms Law

What this deck covers

This deck focuses on 4c Circuit Elements Ohms Law, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Chemical and Physical Foundations of Biological Systems.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: Identify the equivalent resistance of three identical resistors $R$ connected in parallel.

Answer: $R_{\text{eq}} = \frac{R}{3}$. For identical parallel resistors, equivalent resistance equals individual resistance divided by the number.

Flashcard 2: Find the power dissipated by a $6\,\Omega$ resistor with a $12\,\text{V}$ drop across it.

Answer: $P = 24\,\text{W}$. Power dissipation is voltage squared divided by resistance.

Flashcard 3: What circuit quantity is the same through all elements in a series connection?

Answer: Current $I$ is the same through each series element. In series circuits, conservation of charge ensures identical current through all elements.

Flashcard 4: State Kirchhoff's voltage law (KVL) for a closed loop in a circuit.

Answer: $\sum \Delta V = 0$ around any closed loop. Kirchhoff's voltage law upholds energy conservation, summing potential differences to zero in a closed loop.

Flashcard 5: State the power dissipated by a resistor in terms of voltage and resistance.

Answer: $P = \frac{V^2}{R}$. Power in a resistor also derives from Ohm's law, expressed as voltage squared divided by resistance.

Flashcard 6: Find the equivalent resistance of $2\,\Omega$ and $3\,\Omega$ connected in series.

Answer: $R_{\text{eq}} = 5\,\Omega$. Equivalent resistance in series is the sum of individual resistances.

Flashcard 7: What is the SI unit of electric potential difference (voltage), expressed using base SI units?

Answer: Volt (V); $1\,\text{V} = 1\,\text{J}\,\text{C}^{-1}$. Voltage represents the potential energy difference per unit charge, equivalent to one joule per coulomb.

Flashcard 8: State the formula for equivalent resistance of resistors in parallel.

Answer: $\frac{1}{R_{\text{eq}}} = \frac{1}{R_1} + \frac{1}{R_2} + \cdots$. In parallel, reciprocals of resistances add due to increased conductance from multiple paths.

Flashcard 9: State the formula for Ohm's law relating voltage, current, and resistance.

Answer: $V = IR$. Ohm's law states that potential difference is directly proportional to current, with resistance as the proportionality constant.

Flashcard 10: State the formula for equivalent resistance of resistors in series.

Answer: $R_{\text{eq}} = R_1 + R_2 + \cdots$. In series, resistances add because the same current flows through each, accumulating opposition.

Flashcard 11: What is the SI unit of electric current, and what does it represent in terms of charge flow?

Answer: Ampere (A); $1\,\text{A} = 1\,\text{C}\,\text{s}^{-1}$. Electric current measures the rate of charge flow, defined as one coulomb per second in SI units.

Flashcard 12: State the formula for electrical energy transferred over time by a circuit element.

Answer: $E = Pt$. Electrical energy is the product of power and time for constant power dissipation.

Flashcard 13: What is the definition of an ohmic device in terms of the $I$-$V$ relationship?

Answer: It has constant $R$; $I \propto V$ (linear $I$-$V$ curve). An ohmic device obeys Ohm's law with constant resistance, yielding a linear current-voltage relationship.

Flashcard 14: Find the voltage drop across a $5\,\Omega$ resistor carrying $2\,\text{A}$ of current.

Answer: $V = 10\,\text{V}$. Ohm's law calculates voltage as current multiplied by resistance.

Flashcard 15: State the power dissipated by a resistor in terms of current and resistance.

Answer: $P = I^2R$. For resistors, power dissipation derives from combining Ohm's law with the general power formula, using current squared times resistance.

Flashcard 16: State the formula for electrical power dissipated by a circuit element in terms of $I$ and $V$.

Answer: $P = IV$. Electrical power is the rate of energy transfer, given by the product of current and voltage.

Flashcard 17: What circuit quantity is the same across all branches in a parallel connection?

Answer: Voltage $V$ is the same across each parallel branch. In parallel circuits, branches share the same potential difference due to common connection points.

Flashcard 18: What is the relationship between resistance, resistivity, length, and cross-sectional area?

Answer: $R = \rho\frac{L}{A}$. Resistance scales with material resistivity and length while inversely with cross-sectional area.

Flashcard 19: State Kirchhoff's current law (KCL) for a node in a circuit.

Answer: $\sum I_{\text{in}} = \sum I_{\text{out}}$. Kirchhoff's current law enforces charge conservation at a node, balancing incoming and outgoing currents.

Flashcard 20: If wire cross-sectional area $A$ doubles (same $\rho$ and $L$), how does resistance change?

Answer: $R$ halves: $R \propto \frac{1}{A}$. Resistance is inversely proportional to cross-sectional area, so doubling area halves resistance.

Flashcard 21: Find the current when a $12\,\text{V}$ battery is connected to a $3\,\Omega$ resistor.

Answer: $I = 4\,\text{A}$. Ohm's law gives current as voltage divided by resistance.

Flashcard 22: Find the equivalent resistance of $2\,\Omega$ and $3\,\Omega$ connected in parallel.

Answer: $R_{\text{eq}} = \frac{6}{5}\,\Omega$. Equivalent resistance in parallel is the reciprocal of the sum of reciprocals.

Flashcard 23: What is the SI unit of resistance, expressed using volts and amperes?

Answer: Ohm ($\Omega$); $1\,\Omega = 1\,\text{V}\,\text{A}^{-1}$. Resistance quantifies opposition to current flow, defined as one volt per ampere.

Flashcard 24: If wire length $L$ doubles (same $\rho$ and $A$), how does resistance change?

Answer: $R$ doubles: $R \propto L$. Resistance is directly proportional to length, so doubling length doubles resistance.

Flashcard 25: Find the power dissipated by a $4\,\Omega$ resistor when the current is $3\,\text{A}$.

Answer: $P = 36\,\text{W}$. Power dissipation uses current squared multiplied by resistance.