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Chapter 4: Q24DQ (page 841)
The text states that good thermal conductors are also good electrical conductors. If so, why don鈥檛 the cords used to connect toasters, irons, and similar heat-producing appliances get hot by conduction of heat from the heating element?
The cords don鈥檛 get hot because of the low resistance.
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Two coils have mutual inductance . The current in the first coil increases at a uniform rate of 830 A/S. (a) what is the magnitude of the induced emf in the second coil? Is it constant? (b) Suppose that the current described is in the second coil rather than the first. What is the magnitude of the induced emf in the first coil?
An idealized voltmeter is connected across the terminals of abattery, and arole="math" localid="1655719696009" appliance is also connected across its terminals. If the voltmeter reads (a) how much power is being dissipated by the appliance, and (b) what is the internal resistance of the battery?
Questions: When a thunderstorm is approaching, sailors at sea sometimes observe a phenomenon called 鈥淪t. Elmo鈥檚 fire,鈥� a bluish flickering light at the tips of masts. What causes this? Why does it occur at the tips of masts? Why is the effect most pronounced when the masts are wet? (Hint: Seawater is a good conductor of electricity.)
Electrons in an electric circuit pass through a resistor. The wire on either side of the resistor has the same diameter.(a) How does the drift speed of the electrons before entering the resistor compare to the speed after leaving the resistor? (b) How does the potential energy for an electron before entering the resistor compare to the potential energy after leaving the resistor? Explain your reasoning.
A typical small flashlight contains two batteries, each having an emf of, connected in series with a bulb having resistance. (a) If the internal resistance of the batteries is negligible, what power is delivered to the bulb? (b) If the batteries last forwhat 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 to 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 through the filament changes, because this changes the temperature of the filament and hence the resistivity of the filament wire.)
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