7. A parallel combination of a 5.00 2 resistor and an unknown resistor R is connected in series with a 20.0 2 resistor and a battery. This circuit is then disassembled and the three resistors are then connected in series with each other and the same battery. In both arrangements, the current through the 5.00 2 resistor is the same. What is the unknown resistance R? of

7. A parallel combination of a 5.00 2 resistor and an unknown resistor R is connected in series with a 20.0 2 resistor and a battery. This circuit is then disassembled and the three resistors are then connected in series with each other and the same battery. In both arrangements, the current through the 5.00 2 resistor is the same. What is the unknown resistance R? of

Physics for Scientists and Engineers with Modern Physics

10th Edition

ISBN:9781337553292

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter27: Direct-current Circuits

Section: Chapter Questions

Problem 12P: Why is the following situation impossible? A technician is testing a circuit that contains a...

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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 circuit contains a D-cell battery, a switch, a 20- resistor, and three 20-mF capacitors. The capacitors are connected in parallel, and the parallel connection of capacitors are connected in series with the switch, the resistor and the battery, (a) What is die equivalent capacitance of the circuit? (b) What is the KC time constant? (c) How long before the current decreases to 50% of the initial value once the switch is closed?
A 500- resistor, an uncharged 1.50-F capacitor and a 6.16-V emf are connected in series, (a) What is the initial current? (b) What is the RC time constant? (c) What is the current after one time constant? (d) What is the voltage on the capacitor after one time constant?
A student makes a homemade resistor from a graphite pencil 5.00 cm long, where the graphite is 0.05 mm indiameter. The resistivity of the graphite is =1.38102/m . The homemade resistor is place inseries with a switch, a 10.00-mF capacitor and a 0.50-V power source, (a) What is the BC time constant of the circuit? (b) What is the potential drop across the pencil 1.00 s after the switch is closed?
An automobile starter motor has an equivalent resistance of 0.0500 and is supplied by a 12.0-V battery with a 0.0100- internal resistance, (a) What is thecurrent to the motor? (b) What voltage is applied to it? (c) What power is supplied to the motor? (d) Repeat these calculations for when the battery connections are corroded and add 0.0900 to the circuit. (Significant problems are caused by even small amounts of unwanted resistance in low-voltage, high-current applications.)
When resistors with different resistances are connected in parallel, which of the following must be the same for each resistor? Choose all correct answers, (a) potential difference (b) current (c) power delivered (d) charge entering each resistor in a given time interval (e) none of those answers
Three identical 60.0-W, 120-V lightbulbs are connected across a 120-V power source as shown in Figure P28.72. Assuming the resistance of each lightbulb is constant (even though in reality the resistance might increase markedly with current), find (a) the total power supplied by the power source and (b) the potential difference across each lightbulb.
In Figure P29.81, N real batteries, each with an emf and internal resistance r, are connected in a closed ring. A resistor R can be connected across any two points of this ring, causing there to be n real batteries in one branch and N n resistors in the other branch. Find an expression for the current through the resistor R in this case.
Why is the following situation impossible? A technician is testing a circuit that contains a resistance R. He realizes that a better design for the circuit would include a resistance 73R rather than R. He has three additional resistors, each with resistance R. By combining these additional resistors in a certain combination that is then placed in series with the original resistor, he achieves the desired resistance.
A 12.0-V emf automobile battery has a terminal voltage of 16.0 V when being charged by a current of 10.0 A. (a) What is the battery’s internal resistance? (b) What power is dissipated inside the battery? (c) At what rate (in °C/min ) will its temperature increase if its mass is 20.0 kg and it has a specific heat of 0.300 kcal/kg • °C, assuming no heat escapes?
In the circuit of Figure P27.20, the current I1 = 3.00 A and the values of for the ideal battery and R are unknown. What are the currents (a) I2 and (b) I3? (c) Can you find the values of and R? If so, find their values. If not, explain. Figure P27.20
In the circuit of Figure P18.22, the current I1 is 3.0 A and the values of and R are unknown. What are the currents I2 and I3? Figure P18.22