27. Resistors & DC Circuits

Power in Circuits

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A circuit maintains a constant resistance. If the current in the circuit is doubled, what is the effect on the power dissipated by the circuit?
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Two resistors, $R_{1}$ and $R_{2}$ , are connected in series to a constant voltage source such that $R_{1} > R_{2}$ . Which resistor dissipates more power?
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An incandescent lightbulb produces 100 W of light. If this lightbulb operates at 25% efficiency (meaning that out of all the power it generates, only 25% is released as light), what resistance must the lightbulb have if it operates at 120 V?
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A $30$ -watt light bulb is designed to operate at a voltage of $28$ volts. What is the operating resistance of the bulb?
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In a circuit, a current of $2.0 A$ flows through a resistor of resistance $5.0 Ω$ . What is the total rate at which electrical energy is dissipated in the $5.0 Ω$ resistor?
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In a $120$ -volt circuit, ten identical light bulbs each rated at $60$ watts are connected in parallel. What is the total current (amperage) drawn by the circuit?
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Which quantity in a circuit is defined as the amount of work being done per unit of time?
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A hair dryer operates at 120 V (the voltage produced by a household outlet), and outputs 1200 W of energy. For this problem, treat the hair dryer as a single resistor.
(a) At what current does the hair dryer operate?
(b) What is the resistance of the hair dryer?
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A certain resistor is connected across a $9.0 V$ battery and dissipates $20 W$ of power. The battery is replaced with an $18 V$ battery. How much power is dissipated in the resistor now?
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A $1.4 kW$ toaster is connected to a wall outlet, which provides a potential difference of $120 V$ . What is the effective resistance of the toaster?
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