9. Work & Energy

If the heating element of an electric dryer is rated at $4.1\mathrm{kW}$ when connected to a $240V$ line, what is the current drawn by the dryer?

An electric device uses $650$ watts of power. If the voltage across the device is $120$ volts, what is the current flowing through the device?

Which of the following statements about $\mathrm{power}$ is true?

A $100\bullet W$ light bulb operates for $1 \mathrm{hour}$. How many $J$ of energy does it consume during that time?

If a monochromatic light source has a power output of $1 W$ (where $1 W=1 J/s$), and each photon has energy $E$, how many photons are emitted per second?

If two identical light bulbs, A and B, are connected in series to a battery and a switch is connected in parallel with bulb B, how much power does bulb A dissipate when the switch is open?

Which of the following expressions correctly represents the average power delivered by a force acting on an object over a time interval $\Delta t$ with work done $W$?

Which physical quantity is measured in watts ($W$)?

An electric furnace is rated at $15\mathrm{kW}$ and operates on $240V$. What is the rate at which it produces heat output?

A current of $3A$ flows through a resistor of resistance $2\Omega$. How much power is dissipated by the $2\Omega$ resistor?

How many watts of power are required to exert a force of $30N$ over a distance of $100m$ in $1\mathrm{minute}$?

For a hydroelectric turbine, what is the maximum possible power output if water of density $\rho$ flows at a rate $Q$ from a height $h$ above the turbine, assuming 100% efficiency and neglecting losses?

Which of the following is the best estimate for the power usage (in $W$) of a typical electric oven?

Which of the following is the best estimate for the power ($P$) in watts ($W$) of a typical household bread toaster?

If a device uses $280 W$ of power continuously for one day, how much energy in kilowatt-hours does it consume in that day?