AP Physics C: Electricity and Magnetism Flashcards: Compound Direct Current Circuits
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 16 cards to help you master important concepts.
What is the formula for the equivalent resistance ($R_{eq,s}$) of resistors connected in series?
The equivalent resistance of resistors in series is the sum of the individual resistances: $R_{eq,s}=\sum_{i}R_i$.
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What is the formula for the equivalent resistance ($R_{eq,s}$) of resistors connected in series?
The equivalent resistance of resistors in series is the sum of the individual resistances: $R_{eq,s}=\sum_{i}R_i$.
Two resistors of 10 Ω and 15 Ω are connected in parallel. What is their equivalent resistance?
Using the parallel formula, 1/Req = 1/10 + 1/15 = 3/30 + 2/30 = 5/30. Therefore, Req = 30/5 = 6 Ω.
Why is it important for an ideal ammeter to have zero resistance?
Zero resistance ensures that adding the ammeter into the circuit does not increase the total resistance, which would decrease and alter the current it is trying to measure.
What happens to the potential difference across the terminals of a nonideal battery when current is drawn from it?
The potential difference across the terminals is reduced relative to the potential difference when there is no current in the battery.
What is meant by the 'equivalent resistance' of a circuit?
Equivalent resistance is the single resistance value that could replace a more complex network of resistors and result in the same total current and potential difference.
What is the resistance of an ideal voltmeter?
An ideal voltmeter has infinite resistance so that no charge flows through it.
Why is an ammeter placed in series to measure current?
An ammeter is placed in series so that all the charge flowing through that part of the circuit must also flow through the ammeter to be measured.
How is the internal resistance of a nonideal battery modeled in a circuit?
The internal resistance is treated as a resistor in series with an ideal battery and the remainder of the circuit.
Why is it important for an ideal voltmeter to have infinite resistance?
Infinite resistance ensures that no current is diverted from the main circuit through the voltmeter, which would alter the potential difference being measured.
Three resistors of 2 Ω, 4 Ω, and 6 Ω are connected in series. What is their equivalent resistance?
The equivalent resistance is the sum of the individual resistances: 2 Ω + 4 Ω + 6 Ω = 12 Ω.
Why is a voltmeter placed in parallel to measure potential difference?
A voltmeter is placed in parallel to measure the potential difference between two points, connecting across the component without altering the main current path.
A battery has an EMF of 1.5V. When connected to a circuit, its terminal voltage is measured to be 1.4V. What does this indicate?
This indicates the battery is nonideal and has internal resistance, causing a 0.1V potential drop inside the battery when current is flowing.
What is the formula for the equivalent resistance ($R_{eq,p}$) of resistors connected in parallel?
The inverse of the equivalent resistance in parallel is the sum of the inverses of the individual resistances: $\frac{1}{R_{eq,p}}=\sum_{i}\frac{1}{R_i}$.
What is the equation for the terminal voltage ($\Delta V_{terminal}$) of a nonideal battery?
The terminal voltage is the battery's EMF ($\mathcal{E}$) minus the potential drop across its internal resistance ($r$): $\Delta V_{terminal}=\mathcal{E}-Ir$.
What is the resistance of an ideal ammeter?
An ideal ammeter has zero resistance so it does not affect the current it is measuring.
A 9V battery has an internal resistance of 0.2 Ω. What is its terminal voltage when supplying a current of 1.5A?
Using $\Delta V_{terminal}=\mathcal{E}-Ir$, the voltage is 9V - (1.5A)(0.2Ω) = 8.7V.