Physics 123 Exam #2 Fall 2002
Do any THREE of the following four questions. X-OUT the question you OMIT.

1. A battery with a 12.0 V emf and an internal resistance of 1.70 Ω is connected to two resistors R1 = 36.0 Ω and R2 = 48.0 Ω as shown.

(A) What is the current flow through the battery ?
Ans:{539 mA}

(B) What is the voltage drop across resistor R1?
Ans:{11.1 V}

(C) How many joules of heat energy is dissipated by resistor R2 in 4.90 minutes ?
Ans:{752 J}

2. Three capacitors are connected to an 18.0 V battery as shown in the circuit.
(A) What is the total charge stored by all the capacitors?
Ans:{239 mC}

(B) What is the voltage drop across the third capacitor C3 ?
Ans:{14.9 V}

(C) What is the energy of the electric field stored in first capacitor C1?
Ans:{150 mJ}

3. A 90.0 V battery and a 240 V battery (with no internal resistances) are connected to three resistors R1 = 22.0 kΩ, R2 = 87.0 kΩ, and R3 = 51.0 kΩ as shown.
(A) What is the current through resistor R2 ?
Ans:{826 mA}

(B) What is the voltage drop across resistor R3 ?
Ans:{150 V}

(C) What is the total power delivered by both the batteries in this circuit ?
Ans:{515 mW}

4. A 54.0 V battery is used to charge up the two parallel capacitors C1 = 450 nF and C2= 370 nF that are connected to two resistors R1 = 7.90 kΩ and R2 = 22.0 kΩ as shown.
(A) What is the time constant of this circuit ?
Ans:{24.5 ms}

(B) What is the charge on capacitor C1, 8.30 ms after the switch is closed ?
Ans:{6.98 mC}

(C) How long after the switched is closed will it take until the voltage across resistor R2 is 10.0 Volts ?
Ans:{33.8 ms}


Physics 123 Exam #2 Spring 2002

1. If it takes 1.80 ns (nanoseconds) for ten billion electrons to flow through resistor R1 in the circuit shown,

(A) What is the current flowing through resistor R1 ?
Ans:{889 mA}

(B) What is the magnitude of emf source e ?
Ans:{56.0 V}

(C) What is what is the current flowing through the emf source e ?
Ans:{1.19 A}
2. When the circuit is closed and at steady state, the resistor dissipates 26.0 Joules of energy each second.
(A) What is the value of the resistance of the resistor ?
Ans:{22.2 W}

(B) What is the charge on capacitor C1 ?
Ans:{465 nC}

(C) If the battery is disconnected from the circuit by opening the switch, how long will it take for the voltage drop across the resistor to equal 10.0 V ?
Ans:{376 ns}
3. For the circuit shown:
(A) What is the current flowing through resistor R1?
Ans:{6.33 mA}

(B) What is the current flow through the emf source e2?
Ans:{992 mA}

(C) What is the current flow through resistor R4?
Ans:{625 mA}
4. For the circuit shown to the left:
(A) What is the charge on capacitor C3 ?
Ans:{540 mC}

(B) What is the voltage drop across capacitor C1?
Ans:{21.6 V}

(C) How much joules of energy are stored in all the capacitors ?
Ans:{18.3 mJ}