## DC Circuits

Homework Assignment

Questions2, 4, 5, 6, 8, 9, 28

Problems1, 2, 14, 15, 19, 20, 28, 41, 42, 45, 50

Q2Under what condition does the potential difference across the terminals of a battery equal its emf? Can the terminal voltage ever exceed the emf?

Q4Two sets of Christmas-tree lights are available. For setA, when one bulb is removed (or burns out), the remaining bulbs remain illuminated. For setB, when one bulb is removed, the remaining bulbs do not operate. Explain the differnce in wiring of the two sets.

Q5How would you connect resistors so that the equivalent resistance islargerthan the individual resistance?

Q6How would you connect resistors so that the equivalent resistance issmallerthan the individual resistance?

Q8When resistors are connected inseries,which of the following would be thesamefor each resistor: potential difference, current, power?

Q9When resistors are connected inparallel,which of the following would be thesamefor each resistor: potential difference, current, power?

Q28A series circuit consists of three identical lamps connected to a battery as in Figure 28.29. When the switch S is closed, what happens(a) to the intensities of lamps A and B;

(b) to the intensity of lamp C;

(c) to the current in the circuit; and

(d) to the voltage drop across the three lamps?

(e) Does the power dissipated in the circuit increase, decrease or remain the same?

28.1A battery with an emf of 12 V and an internal resistance of 0.90 ohms is connected across a load resistor R.(a) If the current in the circuit is 1.4 A, what is the value of R?

(b) What power is dissipated in the internal resistance of the battery?

28.2A 9.00-V battery deliver 117 mA when connected to a 72.0-ohm laod. Determine the internal resistance of the battery.

28.14(a) Find the equivalent resistance between points a and b in Figure P28.14(b) If a potential difference of 34 V is applied between points a and b, calculate the current in

eachresistor.

28.15The resistance between terminals a and b inFigure P28.15 is 75-ohms. If the resistors labeled R have the same value, determine R.

28.19Calculate the power dissipated in each resistor in the circuit of Figure P28.19.

28.20Determine the equivalent resistance between the terminals a and b for the network illustrated inFigure P28.20.

28.28In the circuit of Figure P28.28, determine the current in each resistor and the voltage across the 200-ohm resistor.

28.41A fully charged capacitor stores 12 J of energy. How much energy remains when its charge has decreased to half its original value?

28.42Consider a series RC circuit (Figure 28.15) for which R = 1.0 megaohms, C = 5.00 microfarads, and E = 30.0 V. Find(a) the time constant of the circuit and

(b) the maximum charge on the capacitor after the switch is closed.

(c) If the switch is closed at time t = 0, find the current in the resistor 10.0 s later.

28.45A 4.00 megaohm resistor and a 3.00 microfarad capacitor are connected in series with a 12.0 V power supply.(a) What is the time constant for the circuit?

(b) Express the current in the circuit and the charge on the capacitor as functions of time.

28.50A capacitor in an RC circuit is charged to 60% of its maximum value in 0.90 s. What is the time constant of the circuit?

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