A resistor is placed in a circuit with an adjustable voltage source. The voltage across and the current through the resistor and the measurements are shown below. Estimate the resistance of the resistor (in 22). Voltage (V) 3500 2800 2100 1400 700 Ω 2 4 . 6 8 10 Current (A)

A resistor is placed in a circuit with an adjustable voltage source. The voltage across and the current through the resistor and the measurements are shown below. Estimate the resistance of the resistor (in 22). Voltage (V) 3500 2800 2100 1400 700 Ω 2 4 . 6 8 10 Current (A)

Physics for Scientists and Engineers, Technology Update (No access codes included)

9th Edition

ISBN:9781305116399

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter28: Direct-current Circuits

Section: Chapter Questions

Problem 28.21P: Consider the circuit shown in Figure P28.21 on page 860. (a) Find the voltage across the 3.00-0...

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A lightbulb is connected to a variable power supply. As the potential across the bulb is varied, the resulting current and the filaments temperature are measured. The data are listed in Table P28.38. a. Find R for each entry in Table P28.38, and then plot R as a function of T. b. Assume that room temperature is at 293 K. Find R0 (resistance at room temperature). Comment on your result.
A 160F capacitor charged to 450 V is dischargedthrough a 31.2k resistor, (a) Find the time constant.(b)Calculate the temperature increase of the resistor, given that its mass is 2.50 g and its specific heat is 1.67kJ/kg °C,noting that most of the thermal energy is retained in the short time of the discharge, (c) Calculate the new resistance, assuming it is pure carbon. (d) Does this change in resistance seem significant?
Resistors are commonly rated at 18W,14W,12W ,1 W and 2 W for use in electrical circuits. If a current of1 = 2.00 A is accidentally passed through a R=1.00 resistor rated at 1 W, what would be the most probable outcome? Is there anything that can be done to prevent such an accident?
Consider a series RC circuit as in Figure P28.38 for which R = 1.00 M, C = 5.00 F, and = 30.0 V. Find (a) the time constant of the circuit and (b) the maximum charge on the capacitor after the switch is thrown closed. (c) Find the current in the resistor 10.0 s after the switch is closed.
Four resistors are connected to a battery as shown in Figure P21.40. The current in the battery is I, the battery emf is , and the resistor values are R1 = R, R2 = 2R, R3 = 4R, and R4 = 3R. (a) Rank the resistors according to the potential difference across them, from largest to smallest. Note any cases of equal potential differences. (b) Determine the potential difference across each resistor in terms of . (c) Rank the resistors according to the current in them, from largest to smallest. Note any cases of equal currents. (d) Determine the current in each resistor in terms of I. (e) If R3 is increased, what happens to the current in each of the resistors? (f) In the limit that R3 , what are the new values of the current in each resistor in terms of I, the original current in the battery? Figure P21.40
The student engineer of a campus radio station wishes to verify the effectiveness of the lightning rod on the antenna mast (Fig. P21.71). The unknown resistance Rx is between points C and E. Point E is a true ground, but it is inaccessible for direct measurement because this stratum is several meters below the Earths surface. Two identical rods are driven into the ground at A and B, introducing an unknown resistance Ry. The procedure is as follows. Measure resistance R1 between points A and B, then connect A and B with a heavy conducting wire and measure resistance R2 between points A and C. (a) Derive an equation for Rx in terms of the observable resistances, R1 and R2. (b) A satisfactory ground resistance would be Rx 2.00 . Is the grounding of the station adequate if measurements give R1 = 13.0 and R2 = 6.00 ? Explain. Figure P21.71
Figure P18.19 shows a Wheatstone bridge, a circuit used to precisely measure an unknown resistance R by varying Rvar until the ammeter reads zero current and the bridge is said to be balanced. If the bridge is balanced with Rvar = 9.00 , find (a) the value of the unknown resistance Rand (b) the current in the 1.00 resistor. (Hint: With the bridge balanced, the wire through the ammeter can effectively be removed from the circuit, leaving two pairs of resistors in parallel.) Figure Pl8.19
Ralph has three resistors, R1, R2, and R3, connected in series. When connected to an ideal emf source E1, current I1 flows through the resistors. a. If the resistors are instead connected to a second source with E2=2E1, what is the new current through the resistors in terms of the first current? b. Show that, if each resistance is doubled and the resistors are connected in series to the second emf source, the current through the resistors is equal to I1.
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?
A capacitor with initial charge Q0 is connected across a resistor R at time t = 0. The separation between the plates of the capacitor changes as d = d0/(1 + t) for 0 t 1 s. Find an expression for the voltage drop across the capacitor as a function of time.
Figure P18.19 shows a Wheatstone bridge, a circuit used to precisely measure an unknown resistance R by varying Rvar until the ammeter reads zero current and the bridge is said to be balanced. If the bridge is balanced with Rvar = 9.00 , find (a) the value of the unknown resistance Rand (b) the current in the 1.00 resistor. (Hint: With the bridge balanced, the wire through the ammeter can effectively be removed from the circuit, leaving two pairs of resistors in parallel.) Figure Pl8.19
When resistors with different resistances are connected in series, 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