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Chapter 4: Q3DQ (page 840)
A cylindrical rod has resistivity . If we triple its length and diameter, what is its resistivity in terms ofrole="math" localid="1655715631515" .
Resistivity remains constant.
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A circular area with a radius oflies in the xy-plane. What is the magnitude of the magnetic flux through this circle due to a uniform magnetic fieldlocalid="1655727900569" (a) in the direction of +z direction; (b) at an angle offrom the direction; (c) in the direction?
In the circuit of Fig. E25.30, the 5.0 Ω resistor is removed and replaced by a resistor of unknown resistance R. When this is done, an ideal voltmeter connected across the points band creads 1.9 V. Find (a) the current in the circuit and (b) the resistance R. (c) Graph the potential rises and drops in this circuit (see Fig. 25.20).
In Europe the standard voltage in homes is 220 V instead of the 120 used in the United States. Therefore a “100-W” European bulb would be intended for use with a 220-V potential difference (see Problem 25.36). (a) If you bring a “100-W” European bulb home to the United States, what should be its U.S. power rating? (b) How much current will the 100-W European bulb draw in normal use in the United States?
BIO The average bulk resistivity of the human body (apart from surface resistance of the skin) is about . The conducting path between the hands can be represented approximately as a cylinder 1.6 m long and 0.10 m in diameter. The skin resistance can be made negligible bysoaking the hands in salt water. (a) What is the resistance between the hands if the skin resistance is negligible? (b) What potential difference between thehands is needed for a lethal shock current of 100 mA ? (Note that your result shows that small potential differences produce dangerous currents when the skin is damp.) (c) With the current in part (b),what power is dissipated in the body?
The potential difference across the terminals of a battery is 8.40 V when there is a current of 1.50 A in the battery from the negative to the positive terminal. When the current is 3.50 A in the reverse direction, the potential difference becomes10.20 V . (a) What is the internal resistance of the battery? (b) What is the emf of the battery?
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