Compound Direct Current Circuits - AP Physics C Electricity and Magnetism

1. What is the formula for resistance using resistivity?

   $R = \rho \frac{L}{A}$. Resistance depends on material properties and geometry.

2. Determine the voltage across a 6 Ω resistor with 3 A current.

   18 V. Using Ohm's Law: $V = 3 \times 6 = 18$ V.

3. What does an ammeter measure in a circuit?

   Current. Ammeter measures the flow of electric charge.

4. Find the total resistance of a 5 Ω and 10 Ω resistor in parallel.

   $\frac{10}{3}$ Ω. Parallel formula: $\frac{1}{R} = \frac{1}{5} + \frac{1}{10} = \frac{3}{10}$.

5. What is the equivalent capacitance in series?

   $\frac{1}{C_{\text{total}}} = \frac{1}{C_1} + \frac{1}{C_2} + \text{...} + \frac{1}{C_n}$. Capacitors in series behave like resistors in parallel.

6. What is the equivalent capacitance in parallel?

   $C_{\text{total}} = C_1 + C_2 + \text{...} + C_n$. Capacitors in parallel add their capacitances directly.

7. What does a voltmeter measure in a circuit?

   Voltage (potential difference). Voltmeter measures potential difference between two points.

8. Find the equivalent capacitance of two 4 F capacitors in parallel.

   8 F. Parallel capacitors add: $4 + 4 = 8$ F.

9. Determine the power dissipated by a 5 Ω resistor with 2 A current.

   20 W. Using $P = I^2R$: $(2)^2 \times 5 = 20$ W.

10. What is the formula for current in a resistor using Ohm's Law?

    $I = \frac{V}{R}$. Rearranged form of Ohm's Law solving for current.

11. Find the total capacitance of three 3 F capacitors in series.

    1 F. Three equal capacitors in series: $\frac{3}{3} = 1$ F.

12. Identify the unit of electric potential.

    Volt ($\text{V}$). Standard unit for electrical potential difference.

13. Identify the unit of resistance.

    Ohm ($\text{Ω}$). Standard unit for electrical resistance.

14. Identify the unit of capacitance.

    Farad ($\text{F}$). Standard unit for electrical capacitance.

15. Find the total resistance of three 6 Ω resistors in series.

    18 Ω. Series resistors add: $6 + 6 + 6 = 18$ Ω.

16. Identify the effect of internal resistance on terminal voltage.

    Reduces terminal voltage. Internal resistance causes voltage drop across the battery.

17. What is the energy dissipation formula in a resistor?

    $P = I^2R$. Power dissipated in resistor using current squared.

18. What is Kirchhoff's Junction Rule?

    The total current entering a junction equals the total current leaving. Conservation of charge at circuit junctions.

19. Determine the current if 200 W is used by a 50 V device.

    4 A. Using $I = \frac{P}{V}$: $\frac{200}{50} = 4$ A.

20. What is the formula for the potential difference across a resistor?

    $V = IR$. Voltage drop across a resistor follows Ohm's Law.

21. Find the total resistance of three 6 Ω resistors in parallel.

    2 Ω. Three equal resistors in parallel: $\frac{6}{3} = 2$ Ω.

22. Identify the unit of electric current.

    Ampere ($\text{A}$). Standard unit for rate of charge flow.

23. What is Kirchhoff's Loop Rule?

    The sum of the voltages around any closed loop is zero. Conservation of energy in closed circuit loops.

24. Find the equivalent capacitance of two 4 F capacitors in series.

    2 F. Series capacitors: $\frac{1}{C} = \frac{1}{4} + \frac{1}{4} = \frac{1}{2}$.

25. Calculate the power used by a 12 Ω resistor with 4 A current.

    192 W. Using $P = I^2R$: $(4)^2 \times 12 = 192$ W.

26. What is the formula for current using power and voltage?

    $I = \frac{P}{V}$. Rearranged power formula solving for current.

27. What is the formula for energy stored in a capacitor?

    $E = \frac{1}{2} C V^2$. Energy stored is proportional to capacitance and voltage squared.

28. What is the formula for power in a circuit?

    $P = IV$. Power equals current times voltage.

29. What is the formula for total resistance in series circuits?

    $R_{\text{total}} = R_1 + R_2 + \text{...} + R_n$. Resistors in series add their resistances directly.

30. Calculate the voltage drop across a 4 Ω resistor with 2 A current.

    8 V. Using Ohm's Law: $V = 2 \times 4 = 8$ V.

31. Find the total resistance of a 5 Ω and 10 Ω resistor in series.

    15 Ω. Series resistors add: $5 + 10 = 15$ Ω.

32. What is the formula for terminal voltage of a battery?

    $V = \text{emf} - Ir$. Terminal voltage decreases due to internal resistance drop.

33. Calculate the energy stored in a 2 F capacitor with 3 V across it.

    9 J. Using $E = \frac{1}{2}CV^2$: $\frac{1}{2} \times 2 \times 9 = 9$ J.

34. What is the formula for total resistance in parallel circuits?

    $\frac{1}{R_{\text{total}}} = \frac{1}{R_1} + \frac{1}{R_2} + \dots + \frac{1}{R_n}$. In parallel, reciprocals of resistances add.

35. What is the formula for resistors with equal resistance in parallel?

    $R_{\text{total}} = \frac{R}{n}$. For $n$ equal resistors, total resistance is $\frac{R}{n}$.

36. Find the total capacitance of three 3 F capacitors in parallel.

    9 F. Parallel capacitors add: $3 + 3 + 3 = 9$ F.

37. Find the current in a 10 Ω resistor with 5 V across it.

    0.5 A. Using Ohm's Law: $I = \frac{5}{10} = 0.5$ A.

38. State Ohm's Law.

    $V = IR$. Fundamental relationship between voltage, current, and resistance.

39. Determine the total current if 2 A and 3 A enter a junction.

    5 A. Junction rule: currents entering equal currents leaving.

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