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Chapter 21: Problem 29
A current of \(5.00 \mathrm{~mA}\) is enough to make your muscles twitch. Calculate how many electrons flow through your skin if you are exposed to such a current for \(10.0 \mathrm{~s}\).
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A small ball with a mass of \(30.0 \mathrm{~g}\) and a charge of \(-0.200 \mu \mathrm{C}\) is suspended from the ceiling by a string. The ball hangs at a distance of \(5.00 \mathrm{~cm}\) above an insulating floor. If a second small ball with a mass of \(50.0 \mathrm{~g}\) and a charge of \(0.400 \mu \mathrm{C}\) is rolled directly beneath the first ball, will the second ball leave the floor? What is the tension in the string when the second ball is directly beneath the first ball?
When a metal plate is given a positive charge, which of the following is taking place? a) Protons (positive charges) are transferred to the plate from another object. b) Electrons (negative charges) are transferred from the plate to another object. c) Electrons (negative charges) are transferred from the plate to another object, and protons (positive charges) are also transferred to the plate from another object. d) It depends on whether the object conveying the charge is a conductor or an insulator.
A silicon sample is doped with phosphorus at 1 part per \(1.00 \cdot 10^{6} .\) Phosphorus acts as an electron donor, providing one free electron per atom. The density of silicon is \(2.33 \mathrm{~g} / \mathrm{cm}^{3},\) and its atomic mass is \(28.09 \mathrm{~g} / \mathrm{mol}\) a) Calculate the number of free (conduction) electrons per unit volume of the doped silicon. b) Compare the result from part (a) with the number of conduction electrons per unit volume of copper wire (assume each copper atom produces one free (conduction) electron). The density of copper is \(8.96 \mathrm{~g} / \mathrm{cm}^{3},\) and its atomic mass is \(63.54 \mathrm{~g} / \mathrm{mol}\)
Two balls have the same mass of \(0.681 \mathrm{~kg}\) and identical charges of \(18.0 \mu \mathrm{C} .\) They hang from the ceiling on strings of identical length as shown in the figure. If the angle with respect to the vertical of the strings is \(20.0^{\circ}\), what is the length of the strings?
A particle (charge \(=+19.0 \mu C)\) is located on the \(x\) -axis at \(x=-10.0 \mathrm{~cm},\) and a second particle (charge \(=-57.0 \mu \mathrm{C})\) is placed on the \(x\) -axis at \(x=+20.0 \mathrm{~cm} .\) What is the magnitude of the total electrostatic force on a third particle (charge = \(-3.80 \mu \mathrm{C})\) placed at the origin \((x=0) ?\)
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