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 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.)
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 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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