MCAT Physics Practice Test 6: Circuits

1. If a defibrillator passes 15 A of current through a patient's body for 0.1 seconds, how much charge goes through the patient's skin?

• A. 0.15 C
• B. 1.5 C
• C. 15 C
• D. 150 C

2. A charge of 2 μC flows from the positive terminal of a 6 V battery, through a 100 Ω resistor, and back through the battery to the positive terminal. What is the total potential difference experienced by the charge?

• A. 0 V
• B. 0.002 V
• C. 0.2 V
• D. 6 V

3. The resistance of two conductors of equal cross-sectional area and equal lengths are compared, and are found to be in the ratio 1:2. The resistivities of the materials from which they are constructed must therefore be in what ratio?

• A. 1:01
• B. 1:02
• C. 2:01
• D. 4:01

4. A voltaic cell provides a current of 0.5 A when in a circuit with a 3 Ω resistor. If the internal resistance of the cell is 0.1 Ω, what is the voltage across the terminals of the battery when there is no current flowing?

• A. 0.05 V
• B. 1.5 V
• C. 1.505 V
• D. 1.55 V

5. A transformer is a device that takes an input voltage and produces an output voltage that can be either larger or smaller than the input voltage, depending on the transformer design. Although the voltage is changed by the transformer, energy is not, so the input power equals the output power. A particular transformer produces an output voltage that is 300 percent of the input voltage. What is the ratio of the output current to the input current?

• A. 1:03
• B. 3:01
• C. 0.25
• D. 300:01:00

6. Given that R₁ = 20 Ω, R₂ = 4 Ω, R₃ = R₄ = 32 Ω, R₅ = 15 Ω, and R₆ = 5 Ω, what is the total resistance in the circuit shown below?

• A. 0.15 Ω
• B. 6.67 Ω
• C. 16.7 Ω
• D. 60 Ω

7. How many moles of electrons pass through a circuit containing a 100 V battery and a 2 Ω resistor over a period of 10 seconds? (Note: )

• A. 5.18 × 10^–3 moles
• B. 500 moles
• C. 5.18 × 10³ moles
• D. 5.2 × 10⁶ moles

8. In the circuit below, what is the voltage drop across the resistor?

• A.
• B.
• C. 5 V
• D. 7.5 V

9. If the area of a capacitor's plates is doubled while the distance between them is halved, how will the final capacitance (C_f) compare to the original capacitance (C_i)?

• A. C_f = C_i
• B.
• C. C_f = 2C_i
• D. C_f = 4C_i

10. The energy stored in a fully charged capacitor is given by . In a typical cardiac defibrillator, a capacitor charged to 7500 V has a stored energy of 400 J. Based on this information, what is the charge on the capacitor in the cardiac defibrillator?

• A. 1.1 × 10^-5 C
• B. 5 × 10^-2 C
• C. 1.1 × 10^-1 C?
• D. 3.1 × 10⁶ C

11. A 10 Ω resistor carries a current that varies as a function of time as shown. How much energy has been dissipated by the resistor after 5 s?

• A. 40 J
• B. 50 J
• C. 80 J
• D. 120 J

12. In the figure below, six currents meet at point P. What is the magnitude and direction of the current between points P and x?

• A. 2 A, toward x
• B. 2 A, toward P
• C. 10 A, toward x
• D. 10 A, toward P

13. Which of the following will most likely increase the electric field between the plates of a parallel plate capacitor?

• A. Adding a resistor that is connected to the capacitor in series
• B. Adding a resistor that is connected to the capacitor in parallel
• C. Increasing the distance between the plates
• D. Adding an extra battery to the system

14. Each of the resistors shown carries an individual resistance of 4 Ω. Assuming negligible resistance in the wire, what is the overall resistance of the circuit?

• A. 16 Ω
• B. 8 Ω
• C. 4 Ω
• D. 3 Ω

15. Which of the following best characterizes ideal voltmeters and ammeters?

• A. Ideal voltmeters and ammeters have infinite resistance.
• B. Ideal voltmeters and ammeters have no resistance.
• C. Ideal voltmeters have infinite resistance, and ideal ammeters have no resistance.
• D. Ideal voltmeters have no resistance, and ideal ammeters have infinite resistance.