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?

The five identical bulbs in FIGURE EX28.11 are all glowing. The battery is ideal. What is the order of brightness of the bulbs, from brightest to dimmest? Some may be equal.

A small toaster that operates at 120 V has a heating element made from a 4.4-m-long, 0.70-mm-diameter nichrome wire. The resistivity, density, and specific heat of nichrome are, respectively, 1.5 x 10⁻⁶ Ωm, 8400 kg/m³, and 450 J/kg K.b. If half the heat energy is lost to the air, how long does it take the heating element to warm from 20℃ to 450℃, about the temperature at which it first begins to glow red?

The flash on a compact camera stores energy in a 120 μF capacitor that is charged to 220 V. When the flash is fired, the capacitor is quickly discharged through a lightbulb with 5.0 Ω of resistance.b. At what rate is the lightbulb dissipating energy 250 μs after the flash is fired?

A $1.4\text{kW}$ toaster is connected to a wall outlet, which provides a potential difference of $120\mathrm{V}$. What is the effective resistance of the toaster?

A certain resistor is connected across a $9.0\mathrm{V}$ battery and dissipates $20\mathrm{ W}$ of power. The battery is replaced with an $18\mathrm{V}$ battery. How much power is dissipated in the resistor now?

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. ((b) If the batteries last for 5.0 h, what is the total energy delivered to the bulb?

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?