Consider the following circuit: 2.7 V Μ V 9.4 Ω La A Μ 2.2 Ω 8.0 Ω 32.0 Ω

A small office-building air conditioner operates or 408-V AC and consumes 50.0 kW. (a) What is its effective resistance? (b) What is the cost of running the air conditioner during a hot summer month when it is on 8.00 h per day for 30 days and electricity costs 9.00 cenls/kW h ?

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

(a) What is the resistance of a light bulb that uses an average power of 75.0 W when connected to a 60.0-Hz power source having a maximum voltage of 170. V? (b) What is the resistance of a 100.-W lightbulb?

Figure P29.84 shows a circuit that consists of two identical emf devices. If R1 = R2 = R and the switch is closed, find an expression (in terms of R and ) for the current I that is in the branch from point a to b.

(a) What is the resistance of a 220-V ac short circuit that generates a peak power of 96.8 kW? (b) What would the average power be if the voltage were 120 V ac?

(a) At what two times in the first period following t = 0 does the instantaneous voltage in 60-Hz AC equal Vrms ? (b) V rms?

In the circuit of Figure P21.57, the switch S has been open for a long time. It is then suddenly closed. Take = 10.0 V, R1 = 50.0 k, R2 = 100 k, and C = 10.0 F. Determine the time constant (a) before the switch is closed and (b) after the switch is closed. (c) Let the switch be closed at t = 0. Determine the current in the switch as a function of time.

At one instant, a current of 6.0 A flows through part of a circuit as shown in Figure P33.12. Determine the instantaneous potential difference between points A and B if the current starts to decrease at a constant rate of 1.0 102 A/s. FIGURE P33.12

(a) What is the resistance of a 220-V AC short circuit that generates a peak power of 96.8 kW? (b) What would the average power be if the average power be if the voltage was 120 V AC?