Simple Circuits - AP Physics 2

1. Find the current if $V = 12 \text{V}$ and $R = 4 \text{Ω}$.

   $I = 3 \text{A}$. Using $V = IR$, so $I = V/R = 12/4$.

2. Find the equivalent resistance of $R_1 = 6 \text{Ω}$ and $R_2 = 3 \text{Ω}$ in parallel.

   $R_{eq} = 2 \text{Ω}$. Using parallel formula: $1/R_{eq} = 1/6 + 1/3$.

3. What is the unit of electrical resistance?

   Ohm (Ω). Named after Georg Simon Ohm.

4. Calculate the resistance if $V = 24 \text{V}$ and $I = 3 \text{A}$.

   $R = 8 \text{Ω}$. Using $R = V/I = 24/3$.

5. What happens to power if both voltage and current are doubled?

   Power increases fourfold. Power equals $IV$, so doubling both gives $4P$.

6. State Ohm's Law in terms of voltage, current, and resistance.

   $V = IR$. Voltage equals current times resistance.

7. Calculate the power dissipated by a $4 \text{Ω}$ resistor with $2 \text{A}$ current.

   $P = 16 \text{W}$. Using $P = I^2R = 2^2 \times 4$.

8. What is the effect on resistance if the length of a resistor is doubled?

   Resistance doubles. Resistance is proportional to length.

9. What device is used to measure electric current?

   Ammeter. Connected in series with circuit.

10. What is the unit of electrical power?

    Watt (W). Named after James Watt.

11. What is the direction of conventional current flow?

    From positive to negative. Convention established before electron discovery.

12. Identify the relationship between power, voltage, and resistance.

    $P = \frac{V^2}{R}$. Derived from $P = IV$ and $I = V/R$.

13. What happens to the total resistance in a parallel circuit when more resistors are added?

    It decreases. More paths reduce overall resistance.

14. Identify the formula for electric charge.

    $Q = It$. Charge equals current times time.

15. Calculate the total current if $I_1 = 2 \text{A}$ and $I_2 = 3 \text{A}$ in parallel.

    $I_{total} = 5 \text{A}$. Simple addition of parallel currents.

16. What is the unit of electric potential difference?

    Volt (V). Named after Alessandro Volta.

17. What is Kirchhoff's Loop Rule?

    Sum of potential differences in any closed loop is zero. Conservation of energy principle.

18. What is the unit of electric current?

    Ampere (A). Named after André-Marie Ampère.

19. What is Kirchhoff's Junction Rule?

    Total current entering a junction equals total current leaving. Conservation of electric charge.

20. What is the current through a $12 \text{Ω}$ resistor with $24 \text{V}$ across it?

    $I = 2 \text{A}$. Using $I = V/R = 24/12$.

21. State the formula for equivalent resistance in a parallel circuit.

    $\frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \text{...} + \frac{1}{R_n}$. Reciprocal of sum of reciprocals.

22. What happens to the total resistance in a series circuit when more resistors are added?

    It increases. More resistances add to total resistance.

23. What is the voltage across each resistor in a series circuit?

    It varies depending on resistance. Voltage divides proportionally by resistance.

24. Identify the relationship between power, current, and resistance.

    $P = I^2R$. Derived from $P = IV$ and $V = IR$.

25. Identify the formula for calculating electrical power in a circuit.

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

26. State the formula for equivalent resistance in a series circuit.

    $R_{eq} = R_1 + R_2 + \text{...} + R_n$. Resistances add directly in series.

27. Find the equivalent resistance of $R_1 = 2 \text{Ω}$ and $R_2 = 3 \text{Ω}$ in series.

    $R_{eq} = 5 \text{Ω}$. Series resistances add: $2 + 3 = 5$.

28. What is the effect on current if voltage doubles and resistance remains constant?

    Current doubles. Current is directly proportional to voltage.

29. What is the total current in a parallel circuit?

    Sum of currents through each branch. Kirchhoff's junction rule application.

30. What happens to total voltage in a series circuit with identical voltage sources?

    It adds up. Voltages sum algebraically in series.

31. What type of circuit allows current to flow through multiple paths?

    Parallel Circuit. Multiple current paths available.

32. What is the voltage across each resistor in a parallel circuit?

    It is the same across each resistor. All branches share same voltage source.

33. Calculate the energy used by a $100 \text{W}$ bulb in 2 hours.

    $E = 200 \text{Wh}$. Using $E = Pt = 100 \times 2$.

34. How does internal resistance affect a real battery's voltage?

    Reduces terminal voltage. Internal resistance causes voltage drop.

35. Find the current through a $5 \text{Ω}$ resistor with $15 \text{V}$ across it.

    $I = 3 \text{A}$. Using Ohm's law: $I = V/R = 15/5$.

36. Calculate the power if $V = 10 \text{V}$ and $I = 2 \text{A}$.

    $P = 20 \text{W}$. Using $P = IV = 10 \times 2$.

37. What device is used to measure voltage?

    Voltmeter. Connected in parallel with component.

38. What is the voltage drop across a $10 \text{Ω}$ resistor with $0.5 \text{A}$ current?

    $V = 5 \text{V}$. Using $V = IR = 0.5 \times 10$.

39. What type of circuit has only one path for current flow?

    Series Circuit. Single continuous current path.

40. What is the formula for energy consumed by an electrical device?

    $E = Pt$. Energy equals power times time.

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