AP Physics Circuits

A circuit contains a length of tungsten wire with resistance R. An increase in the resistance would result if which of the following could be decreased?

• The resistivity of the tungsten

• The cross-sectional area of the wire

• The length of the wire

• The temperature of the wire

• The current in the wire

In the circuit shown above, the battery supplies a constant voltage 𝑉 when the switch 𝑆 is closed. The value of the capacitance is 𝐶 , and the value of the resistances are 𝑅₁ and 𝑅₂. A long time after the switch has been closed, the current supplied by the battery is

• V/(R₁ + R₂)

• V/R₁

• V/R₂

• V(R₁ + R₂)/R₁R₂

• zero

The circuit in the figure above contains two identical lightbulbs in series with a battery. At first both bulbs glow with equal brightness. When switch S is closed, which of the following occurs to the bulbs?

• Bulb 1: Goes out

  Bulb 2: Gets brighter

• Bulb 1: Gets brighter

  Bulb 2: Goes out

• Bulb 1: Gets brighter

  Bulb 2: Gets slightly dimmer

• Bulb 1: Gets slightly dimmer

  Bulb 2: Gets brighter

• Bulb 1: Nothing

  Bulb 2: Goes out

An ideal battery is connected to a resistor of variable resistance R. There is an ammeter collecting data on the current I in the circuit. Which of the following graphs and characteristics of the graph would represent the power dissipated in the resistor?

• The slope of the graph of I as a function of 1/R

• The y-intercept of the graph of I as a function of R

• The slope of the graph of I² as a function of 1/R

• The y-intercept of the graph of I² as a function of R

• The slope of the graph of I² as a function of R²

A series circuit is set up with a battery, switch, resistor, capacitor, ammeter, and voltmeter, as shown. The values of the resistor and the capacitor are unknown. Which of the following features of the circuit allow a student to determine the time constant of the circuit?

• The voltmeter is in parallel with the resistor, so its readings can be used to determine the time constant.

• The ammeter is in parallel with the capacitor, so its readings can be used to determine the time constant

• The resistor and the capacitor are in parallel, so their values can be used to determine the time constant

• The resistor and the capacitor are shown in series, so their values can be used to determine the time constant.

• The battery is in series with the resistor and capacitor, so their values can be used to determine the time constant

The circuit above contains four identical lightbulbs connected to a battery. Which of the following procedures would increase the brightness of bulb A and decrease the brightness of bulb D?

I. Replacing bulb B with an open switch

II. Replacing bulb C with a closed switch

III. Replacing the battery with another battery of higher voltage

• I only

• II only

• I and II only

• II and III only

• I, II, and III

Students are instructed to build the circuit shown below. The students want to open and close various switches in the circuit so that the power dissipated in bulb F is at a maximum. Which combination of open and closed switches should they use?

• Switch S3 is open, and switches S1 and S2 are closed

• Switch S1 and S3 are open, and switch S2 is closed

• Switches S2 and S3 are open, and switch S1 is closed

• Switches S1 and S2 are open, and switch S3 is closed

• Switches S1, S2, and S3 are closed

A student has an ohmic lightbulb connected to a battery that has significant internal resistance. As the student connects other identical lightbulbs in parallel to the first lightbulb, which of the following would be a reasonable observation about the brightnesses of the lightbulbs?

• Each lightbulb gets brighter as more lightbulbs are added.

• Each lightbulb gets dimmer as more lightbulbs are added.

• When each lightbulb is added, it is the same brightness as the first lightbulb, which remains the same brightness throughout.

• The first lightbulb remains the same brightness, but each added lightbulb is brighter than the original.

• The first lightbulb remains the same brightness, but each added lightbulb is dimmer than the original.

A resistor of resistance R is connected in a circuit to two identical batteries. The circuit also contains switch S and ideal voltmeter V, as shown in the figure above. The batteries both have an emf ε and internal resistance r. The reading of the voltmeter is noted with the switch in the open position. Which of the following best represents how the voltmeter reading after the switch is closed compares to the reading before the switch is closed?

• The reading of the voltmeter is the same

• The reading of the voltmeter is higher

• The reading of the voltmeter is lower

• Cannot be determined without knowing the internal resistance of the batteries

• Cannot be determined without knowing the emf of the batteries

The three lightbulbs in the circuit above are identical, and the battery has zero internal resistance. When switch S is closed to cause bulb 1 to light, which of the other two bulbs increase(s) in brightness?

• Neither bulb

• Bulb 2 only

• Bulb 3 only

• Both bulbs

• It cannot be determined without knowing the emf of the battery