p240+feb+13+discussion+problems

# p240+feb+13+discussion+problems - V ad in the • circuit...

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25.52 A typical small flashlight contains two batteries, each having an emf of 1.5 V , connected in series with a bulb having resistance 17 Ω. (a) If the internal resistance of the batteries is negligible, what power is delivered to the bulb? (b) If the batteries last for 5.0 h , what is the total energy delivered to the bulb? (c) The resistance of real batteries increases as they run down. If the initial internal resistance is negligible, what is the combined internal resistance of both batteries when the power of the bulb has decreased to half its initial value? (Assume that the resistance of the bulb is constant. Actually, it will change somewhat when the current though the filament changes, because this changes the temperature of the filament and hence the resistivity of the filament wire.)

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25.68 (a) What is the potential difference
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Unformatted text preview: V ad in the • circuit to the right? (b) What is the terminal voltage of the 4.00-V battery? (c) A battery with emf 10.30 V and internal resistance 0.50 Ω is inserted in the circuit at d, with its negative terminal connected to the negative terminal connected to the negative terminal of the 8.00-V battery. What is the difference of potential V bc between the terminals of the 4.00-V battery? • 25.86 A source with emf ξ and internal resistance r is connected to an external circuit. • (a) Show that the power output of the source is maximum when the current in the circuit is one-half the short circuit current of the source. (b) If the external circuit consists of a resistance R , show that the power output is maximum when R = r , and that the maximum power is ξ 2 /(4 r )....
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## This note was uploaded on 02/15/2012 for the course PHYS 240 taught by Professor Winn during the Winter '11 term at University of Michigan.

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p240+feb+13+discussion+problems - V ad in the • circuit...

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