The student engineer of a campus radio station wishes to verify the effectiveness of the lightning rod on the antenna mast (Fig. P27.49). 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 Earth’s 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
Figure P27.49
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Chapter 28 Solutions
Physics for Scientists and Engineers, Technology Update (No access codes included)
- Two conductors are made of the same material and have the same length. Conductor A is a solid wire of diameter 1.0 mm. Conductor B is a hollow tube of outside diameter 2.0 mm and inside diameter 1.0 mm. What is the resistance ratio RA/RB, measured between their ends?arrow_forward1.00 MQ A conducting sphere is charged by an emf source E through a 1.00 MO resistor. When the sphere is fully charged, it has 2 µC charge. The highest current during the charging was I mA. What is the electrical potential energy of the sphere when it is fully charged? Give your answer in mJ.arrow_forwardThe average resistivity of the human body (apart from sur face resistance of the skin) is about 5.0 Ω • m. The conducting path between the right and left hands can be approximated as a cylinder 1.6 m long and 0.10 m in diameter. The skin resistance can be made negligible by soaking the hands in salt water.a. What is the resistance between the hands if the skin resistance is negligible?b. If skin resistance is negligible, what potential difference between the hands is needed for a lethal shock current of 100 mA? Your result shows that even small potential differences can produce dangerous currents when skin is damp.arrow_forward
- Material with uniform resistivity p is formed into a wedge as shown in Figure P26.50. Show that the resistance between face A and face B of this wedge is L R= p In w(y2 – y,) Face A Face B Figure P26.50arrow_forwardA cell membrane has a resistance and a capacitance and thus a characteristic time constant. What is the time constant of a 9.0-nm-thick membrane surrounding a 0.040-mm-diameter spherical cell?arrow_forwardTwo conductors are made of the same material and have the same length. Conductor A is a solid wire of diameter 1.1 mm. Conductor B is a hollow tube of outside diameter 2.5 mm and inside diameter 1.4 mm. What is the resistance ratio RA/RB., measured between their ends? Number Unitsarrow_forward
- What is the time constant of the circuit shown in Figure OQ28.7? Each of the five resistors has resistance R. and each of the five capacitors has capacitance C. The internal resistance of the battery is negligible. (a) RC. (b) 5RC. (c) 10RC (d) 25RC (e) none of those answersarrow_forwardNerve impulses are carried along axons, the elongated fibers that transmit neural signals. We can model an axon as a tube with an inner diameter of 10 μm. The tube wall is insulated, but the fluid inside it has a resistivity of 0.50 Ω⋅m. What is the resistance of a 7.0- mm -long axon?Express your answer with the appropriate units.arrow_forwardIf you touch the two terminals of a power supply with your two fingertips on opposite hands, the potential difference will produce a current through your torso. The maximum safe current is approximately 5 mA.a. If your hands are completely dry, the resistance of your body from fingertip to fingertip is approximately 500 kΩ. If you accidentally touch both terminals of your 120 V household electricity supply with dry fingers, will you receive a dangerous shock?b. If your hands are moist, your resistance drops to approximately 1 kΩ. If you accidentally touch both terminals of your 120 V household supply with moist fingers, will you receive a dangerous shock?arrow_forward
- A 60 W lightbulb has a resistance of 240 Ω. At the operating temperature of the tungsten filament, its resistivity is approximately 5.0 x 10-7 Ω • m. If the wire used to make the filament is 0.040 mm in diameter (a typical value). As described above the length of a 60 W, 240 Ω lightbulb filament was calculated to be 60 cm.a. If the potential difference across the filament is 120 V, what is the strength of the electric field inside the filament?b. Suppose the length of the bulb’s filament were doubled without changing its diameter or the potential difference across it. What would the electric field strength be in this case?c. Remembering that the current in the filament is proportional to the electric field, what is the current in the filament following the doubling of its length?d. What is the resistance of the filament following the doubling of its length?arrow_forwardIn the circuit shown in Figure OQ28.12, each battery is delivering energy to the circuit by electrical transmission. All the resistors have equal resistance. (i) Rank the electric potentials at points a, b. c, d, and e from highest to lowest, noting any cases of equality in the ranking. (ii) Rank the magnitudes of the currents at the same points from greatest to least, noting any cases of equality.arrow_forwardA battery is used to charge a capacitor through a resistor as shown. Show that half the energy supplied by the battery appears as internal energy in the resistor and half is stored in the capacitor.arrow_forward
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