AP Physics C: Mechanics - Ammeter and Voltmeter Quiz

📚 Quick Study Guide

• ⚡ Ammeter: Measures current in a circuit. It is connected in series. An ideal ammeter has zero resistance.
• 📏 Voltmeter: Measures potential difference (voltage) across a circuit element. It is connected in parallel. An ideal voltmeter has infinite resistance.
• 📐 Internal Resistance (Ammeter): A real ammeter has a small internal resistance ($r_A$). The smaller $r_A$ is, the more accurate the reading.
• 📊 Internal Resistance (Voltmeter): A real voltmeter has a large internal resistance ($r_V$). The larger $r_V$ is, the more accurate the reading.
• 🧮 Ammeter in a Circuit: Adding an ammeter in series increases total resistance slightly, but ideally negligibly.
• 💡 Voltmeter in a Circuit: Adding a voltmeter in parallel decreases the equivalent resistance of the section it measures, but ideally negligibly.
• 📝 Formulas:
  • Ohm's Law: $V = IR$
  • Power: $P = IV = I^2R = \frac{V^2}{R}$

Practice Quiz

1. Which of the following statements is true about an ideal ammeter?
   1. It has infinite resistance and is connected in parallel.
   2. It has infinite resistance and is connected in series.
   3. It has zero resistance and is connected in parallel.
   4. It has zero resistance and is connected in series.
2. An ammeter with internal resistance $r_A$ is used to measure the current through a resistor $R$. What is the effect of the ammeter on the measured current?
   1. It increases the measured current.
   2. It decreases the measured current.
   3. It has no effect on the measured current.
   4. It reverses the direction of the current.
3. Which of the following statements is true about an ideal voltmeter?
   1. It has infinite resistance and is connected in parallel.
   2. It has infinite resistance and is connected in series.
   3. It has zero resistance and is connected in parallel.
   4. It has zero resistance and is connected in series.
4. A voltmeter with internal resistance $r_V$ is used to measure the voltage across a resistor $R$. What is the effect of the voltmeter on the measured voltage?
   1. It increases the measured voltage.
   2. It decreases the measured voltage.
   3. It has no effect on the measured voltage.
   4. It makes voltage zero.
5. What is the primary purpose of an ammeter in a circuit?
   1. To measure voltage.
   2. To measure current.
   3. To measure resistance.
   4. To measure power.
6. What is the primary purpose of a voltmeter in a circuit?
   1. To measure voltage.
   2. To measure current.
   3. To measure resistance.
   4. To measure power.
7. An ammeter and a voltmeter are connected to a resistor in a circuit. The ammeter reads 2A and the voltmeter reads 10V. What is the resistance of the resistor?
   1. 2 Ohms
   2. 5 Ohms
   3. 10 Ohms
   4. 20 Ohms