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Chapter 21: Q14CQ (page 771)
Explain which battery is doing the charging and which is being charged in Figure 21.45.
is charged, is doing the charging.
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A \(160 - \mu F\)capacitor charged to \(450\;V\)is discharged through a \(31.2 - k\Omega \)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 \(1.67\frac{{kJ}}{{kg{ \cdot ^\circ }C}}\), 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?
Using the exact exponential treatment, find how much time is required to charge an initially uncharged capacitor through alocalid="1656397542799" resistor toof its final voltage.
(a) Calculate the capacitance needed to get an \(RC\)time constant of \(1.00 \times {10^3}\;s\) with a \(0.100 - \Omega \) resistor. (b) What is unreasonable about this result?(c) Which assumptions are responsible?
Apply the junction rule at point a in Figure 21.52.
Carbon-zinc dry cells (sometimes referred to as non-alkaline cells) have an emf of 1.54 V, and they are produced as single cells or in various combinations to form other voltages. (a) How many 1.54 V cells are needed to make the common 9 V battery used in many small electronic devices? (b) What is the actual emf of the approximately 9 V battery? (c) Discuss how internal resistance in the series connection of cells will affect the terminal voltage of this approximately 9 V battery.
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