Fluids & Electric Circuits

A student has four identical resistors and needs the largest possible resistance for a branch of a circuit. How should the student arrange the resistors to get the largest possible effective resistance?

• Connect all the resistors in series

• Connect all the resistors in parallel

• Connect two of the resistors in parallel and then connect the parallel pair in series with the other two resistors

• Connect three of the resistors in parallel and then connect the parallel set in series with the remaining resistor

A capacitor made of two parallel plates separated by air is charged using a battery. While the battery remains connected, the plates are moved farther apart. How does the magnitude of the final charge on each plate and the energy stored in the capacitor compare to those same quantities before the capacitor plates were moved?

• Charge: Greater

  Energy Stored: Greater

• Charge: Greater

  Energy Stored: The same

• Charge: Less

  Energy Stored: The same

• Charge: Less

  Energy Stored: Less

A student is conducting an experiment to compare the resistivity of two unknown materials by using two wires, each made of one of the materials and each connected in a circuit. The student measures the potential difference across and current in the wires. Which of the following must be the same to be able to compare the resistivities using just the potential difference and current measurements? Select two answers

• The length of each wire

• The cross-sectional area of each wire

• The potential difference across each wire

• The current in each wire

Four cylindrical wires of different sizes are made of the same material. Which of the following combinations of length and cross-sectional area of one of the wires will result in the smallest resistance?

• Length: 3L

  Area: 3a

• Length: 3L

  Area: 6a

• Length: 6L

  Area: 3a

• Length: 6L

  Area: 6a

Cylindrical rods of various lengths and cross-sectional areas are made of different materials. Each rod is connected individually to the same battery, whose potential difference is known, and the current in the circuit is measured. Can the resistivities of the rods be compared?

• Yes, because the lengths and cross-sectional areas of the rods can be measured.

• Yes, because the rods will be connected to the same battery and will have the same currents.

• No, because the resistivity of a material depends on its atomic structure, which is unknown.

• No, because the rods have different lengths.

In an electric circuit, a single wire is connected to three branches that contain resistors. The three branches then connect back to a single wire. The current in each of the single wires is the same. Conservation of which of the following best explains this phenomenon?

• Mass

• Electric charge

• Momentum

• Energy

Which is the correct equation to use when solving for the total resistance in a SERIES circuit?

• Rt = R1 + R2 + R3

• Rt = R1 + R2 - R3

• Rt = (R1 + R2 + R3) / 3

• Rt = V / I

How can you increase the resistance of a wire?

• Lower the resistivity of the material

• Decrease the length of the wire

• Increase the cross sectional area

• Increase the temperature of the wire

Two resistors (R1 = 50 Ω and R2 = 500 Ω) are connected in PARALLEL. What is the resistance of the two resistors together?

• 35 Ω

• 45 Ω

• 50 Ω

• 65 Ω

In the circuit represented above, the current in the 1 Ω resistor is 4 A. What is terminal voltage V of the battery?

• 6 V

• 12 V

• 18 V

• 19 V

• 30 V