1. What is the resistance of the following circuit as seen from the battery? 602 www 12 Ω 402 12 Ω www www w ww 402 302 www 302 702

Consider the circuit below, (a) What is the initial current through resistor R2? when the switch is closed? (b) What is die current through resistor R2 when the capacitor is fully charged, long after die switch is closed? (c) What happens if the switch is opened after it has been closed for some rime? (d) If the switch has been closed for a time period long enough for the capacitor to become fully charged, and then the switch is opened, how long before the current through resistor R1 reaches half of its initial value?

Electric current I enters a node with three resistors connected in parallel (Fig. CQ18.5). Which one of the following is correct? (a) I1 = I and I2 = I3 = 0. (b) I2 I1 and I2 I3. (c) V1 V2 V3 (d) I1 I2 I3 0. Figure CQ18.5

The circuit shown in Figure P28.78 is set up in the laboratory to measure an unknown capacitance C in series with a resistance R = 10.0 M powered by a battery whose emf is 6.19 V. The data given in the table are the measured voltages across the capacitor as a function of lime, where t = 0 represents the instant at which the switch is thrown to position b. (a) Construct a graph of In (/v) versus I and perform a linear least-squares fit to the data, (b) From the slope of your graph, obtain a value for the time constant of the circuit and a value for the capacitance. v(V) t(s) In (/v) 6.19 0 5.56 4.87 4.93 11.1 4.34 19.4 3.72 30.8 3.09 46.6 2.47 67.3 1.83 102.2

Electric current I enters a node with three resistors connected in parallel (Fig. CQ18.5). Which one of the following is correct? (a) I1 = I and I2 = I3 = 0. (b) I2 I1 and I2 I3. (c) V1 V2 V3 (d) I1 I2 I3 0. Figure CQ18.5

(a) Digital medical thermometers determine temperature by measuring the resistance of a semiconductor device called a thermistor (which has a= - 0.0600/°C ) when it is at the same temperature as the patient. What is a patient's temperature if the thermistor’s resistance at that temperature is 82.0% of its value at 37.0°C (normal body temperature)? (b) The negative value for a may not be maintained for very low temperatures. Discuss why and whether this is the case here. (Hint: Resistance can’t become negative.)

A battery with = 6.00 V and no internal resistance supplies current to the circuit shown in Figure P27.9. When the double-throw switch S is open as shown in the figure, the current in the battery is 1.00 mA. When the switch is closed in position a, the current in the battery is 1.20 mA. When the switch is closed in position b, the current in the battery is 2.00 mA. Find the resistances (a) R1, (b) R2, and (c) R3. Figure P27.9 Problems 9 and 10.

(a) What is the unknown emfx in a potentiometer that balances when Rxis 10.0 O, and balances when Rsis 15.0for a standard 3.000-V emf? (b) The same emfx is placed in the same potentiometer, which now balances when Rsis 15.0for a standard emf of 3.100 V. At what resistance Rxwill the potentiometer balance?

The- pair of capacitors in Figure P28.63 are fully charged by a 12.0-V battery. The battery is disconnected, and the switch is then closed. Alter 1.00 ms has elapsed, (a) how much charge remains 011 the 3.00-F capacitor? (b) How much charge remains on the 2.00-F capacitor? (c) What is the current in the resistor at this time?

15. What is the current for the circuit shown? R13 5Ω R17 10 Ω + V2 12 V R16 25 Ω + V1 12 V R15 15 Q ww R14 -20 Q Show your work... wwwwww wwww W R10 30 Ω R11 35 Ω R12 40 Ω