Design Energy Conversion Devices - Physics
Card 1 of 30
What energy conversion is performed by a wind turbine connected to a generator?
What energy conversion is performed by a wind turbine connected to a generator?
Tap to reveal answer
Kinetic (wind) energy to electrical energy. Rotating blades turn generator shaft to induce current.
Kinetic (wind) energy to electrical energy. Rotating blades turn generator shaft to induce current.
← Didn't Know|Knew It →
What is the formula for efficiency in terms of useful output and total input energy?
What is the formula for efficiency in terms of useful output and total input energy?
Tap to reveal answer
$\text{efficiency}=\frac{E_{\text{useful out}}}{E_{\text{total in}}}$. Ratio of useful output to total input energy.
$\text{efficiency}=\frac{E_{\text{useful out}}}{E_{\text{total in}}}$. Ratio of useful output to total input energy.
← Didn't Know|Knew It →
What is the formula for efficiency in terms of useful output and total input power?
What is the formula for efficiency in terms of useful output and total input power?
Tap to reveal answer
$\text{efficiency}=\frac{P_{\text{useful out}}}{P_{\text{total in}}}$. Same ratio applies to power since $P = E/t$.
$\text{efficiency}=\frac{P_{\text{useful out}}}{P_{\text{total in}}}$. Same ratio applies to power since $P = E/t$.
← Didn't Know|Knew It →
Identify the correct unit for power used when evaluating energy-conversion devices.
Identify the correct unit for power used when evaluating energy-conversion devices.
Tap to reveal answer
Watt (W). SI unit for power is joules per second.
Watt (W). SI unit for power is joules per second.
← Didn't Know|Knew It →
What energy conversion is performed by a photovoltaic (solar) cell?
What energy conversion is performed by a photovoltaic (solar) cell?
Tap to reveal answer
Radiant (light) energy to electrical energy. Photons excite electrons across semiconductor junction.
Radiant (light) energy to electrical energy. Photons excite electrons across semiconductor junction.
← Didn't Know|Knew It →
What is the term for a device that converts mechanical rotation into electrical energy?
What is the term for a device that converts mechanical rotation into electrical energy?
Tap to reveal answer
Generator. Uses electromagnetic induction to produce current from rotation.
Generator. Uses electromagnetic induction to produce current from rotation.
← Didn't Know|Knew It →
What is the term for a device that converts electrical energy into mechanical rotation?
What is the term for a device that converts electrical energy into mechanical rotation?
Tap to reveal answer
Electric motor. Uses electromagnetic forces to create rotational motion.
Electric motor. Uses electromagnetic forces to create rotational motion.
← Didn't Know|Knew It →
What energy conversion is performed by a loudspeaker playing sound from an audio signal?
What energy conversion is performed by a loudspeaker playing sound from an audio signal?
Tap to reveal answer
Electrical energy to sound energy. Current through coil creates magnetic field that moves cone.
Electrical energy to sound energy. Current through coil creates magnetic field that moves cone.
← Didn't Know|Knew It →
What energy conversion is performed by an electric resistance heater (idealized)?
What energy conversion is performed by an electric resistance heater (idealized)?
Tap to reveal answer
Electrical energy to thermal energy. Current through resistor dissipates energy as heat.
Electrical energy to thermal energy. Current through resistor dissipates energy as heat.
← Didn't Know|Knew It →
What is the correct expression for electrical energy transferred when power is constant for time $t$?
What is the correct expression for electrical energy transferred when power is constant for time $t$?
Tap to reveal answer
$E=Pt$. Energy equals power multiplied by time duration.
$E=Pt$. Energy equals power multiplied by time duration.
← Didn't Know|Knew It →
Identify the main wasted energy output to reduce when designing a more efficient electric motor.
Identify the main wasted energy output to reduce when designing a more efficient electric motor.
Tap to reveal answer
Thermal energy from resistive heating and friction. These losses reduce motor efficiency below 100%.
Thermal energy from resistive heating and friction. These losses reduce motor efficiency below 100%.
← Didn't Know|Knew It →
Calculate wasted power if $P_{\text{in}}=500,\text{W}$ and efficiency is $0.70$.
Calculate wasted power if $P_{\text{in}}=500,\text{W}$ and efficiency is $0.70$.
Tap to reveal answer
$150,\text{W}$. $P_{waste} = P_{in} - P_{out} = 500 - (0.70 × 500) = 150$ W.
$150,\text{W}$. $P_{waste} = P_{in} - P_{out} = 500 - (0.70 × 500) = 150$ W.
← Didn't Know|Knew It →
Calculate input power if efficiency is $0.40$ and useful output power is $120,\text{W}$.
Calculate input power if efficiency is $0.40$ and useful output power is $120,\text{W}$.
Tap to reveal answer
$300,\text{W}$. $P_{in} = P_{out}/\text{eff} = 120/0.40 = 300$ W.
$300,\text{W}$. $P_{in} = P_{out}/\text{eff} = 120/0.40 = 300$ W.
← Didn't Know|Knew It →
Calculate efficiency if $P_{\text{useful}}=60,\text{W}$ and $P_{\text{in}}=80,\text{W}$.
Calculate efficiency if $P_{\text{useful}}=60,\text{W}$ and $P_{\text{in}}=80,\text{W}$.
Tap to reveal answer
$0.75$. Efficiency = $60/80 = 0.75$ using power ratio formula.
$0.75$. Efficiency = $60/80 = 0.75$ using power ratio formula.
← Didn't Know|Knew It →
What is the correct expression for electrical power in a circuit using voltage and current?
What is the correct expression for electrical power in a circuit using voltage and current?
Tap to reveal answer
$P=VI$. Power equals voltage times current in DC circuits.
$P=VI$. Power equals voltage times current in DC circuits.
← Didn't Know|Knew It →
Which option best describes a Sankey diagram in energy-device design?
Which option best describes a Sankey diagram in energy-device design?
Tap to reveal answer
A diagram showing energy inputs, useful outputs, and wasted transfers. Width of arrows shows relative energy flow amounts.
A diagram showing energy inputs, useful outputs, and wasted transfers. Width of arrows shows relative energy flow amounts.
← Didn't Know|Knew It →
What energy conversion is performed by a microphone converting sound to a signal?
What energy conversion is performed by a microphone converting sound to a signal?
Tap to reveal answer
Sound energy to electrical energy. Sound waves vibrate diaphragm, inducing current in coil.
Sound energy to electrical energy. Sound waves vibrate diaphragm, inducing current in coil.
← Didn't Know|Knew It →
What energy conversion is performed by an LED when it is operating normally?
What energy conversion is performed by an LED when it is operating normally?
Tap to reveal answer
Electrical energy to radiant (light) energy. Current through semiconductor junction emits photons.
Electrical energy to radiant (light) energy. Current through semiconductor junction emits photons.
← Didn't Know|Knew It →
What energy conversion is performed by a battery while powering a circuit?
What energy conversion is performed by a battery while powering a circuit?
Tap to reveal answer
Chemical energy to electrical energy. Redox reactions create electron flow through circuit.
Chemical energy to electrical energy. Redox reactions create electron flow through circuit.
← Didn't Know|Knew It →
What energy conversion is performed by a hydroelectric dam and turbine-generator system?
What energy conversion is performed by a hydroelectric dam and turbine-generator system?
Tap to reveal answer
Gravitational potential energy to electrical energy. Falling water spins turbines connected to generators.
Gravitational potential energy to electrical energy. Falling water spins turbines connected to generators.
← Didn't Know|Knew It →
Which energy conversion best describes a microphone (sound sensor) producing a signal?
Which energy conversion best describes a microphone (sound sensor) producing a signal?
Tap to reveal answer
Sound energy $\rightarrow$ electrical energy. Sound waves vibrate diaphragm to induce electrical signal.
Sound energy $\rightarrow$ electrical energy. Sound waves vibrate diaphragm to induce electrical signal.
← Didn't Know|Knew It →
Which energy conversion best describes a loudspeaker producing sound from a signal?
Which energy conversion best describes a loudspeaker producing sound from a signal?
Tap to reveal answer
Electrical energy $\rightarrow$ sound energy. Electric current drives cone vibrations to produce sound waves.
Electrical energy $\rightarrow$ sound energy. Electric current drives cone vibrations to produce sound waves.
← Didn't Know|Knew It →
Which energy conversion best describes a hydroelectric dam power station?
Which energy conversion best describes a hydroelectric dam power station?
Tap to reveal answer
Gravitational potential $\rightarrow$ electrical energy. Falling water turns turbines to generate electricity.
Gravitational potential $\rightarrow$ electrical energy. Falling water turns turbines to generate electricity.
← Didn't Know|Knew It →
What is the term for a device that changes energy from one form to another?
What is the term for a device that changes energy from one form to another?
Tap to reveal answer
Energy transducer (energy converter). Converts energy between different forms like electrical to mechanical.
Energy transducer (energy converter). Converts energy between different forms like electrical to mechanical.
← Didn't Know|Knew It →
What is the definition of efficiency for an energy-converting device?
What is the definition of efficiency for an energy-converting device?
Tap to reveal answer
$\text{efficiency}=\frac{\text{useful energy out}}{\text{total energy in}}$. Ratio shows how much input energy becomes useful output.
$\text{efficiency}=\frac{\text{useful energy out}}{\text{total energy in}}$. Ratio shows how much input energy becomes useful output.
← Didn't Know|Knew It →
Which energy conversion best describes an electric motor in normal operation?
Which energy conversion best describes an electric motor in normal operation?
Tap to reveal answer
Electrical energy $\rightarrow$ kinetic (mechanical) energy. Motors use electricity to create rotational motion.
Electrical energy $\rightarrow$ kinetic (mechanical) energy. Motors use electricity to create rotational motion.
← Didn't Know|Knew It →
Which energy conversion best describes a wind turbine connected to a generator?
Which energy conversion best describes a wind turbine connected to a generator?
Tap to reveal answer
Kinetic (wind) $\rightarrow$ electrical energy. Moving air spins blades connected to generator.
Kinetic (wind) $\rightarrow$ electrical energy. Moving air spins blades connected to generator.
← Didn't Know|Knew It →
Which energy conversion best describes an electric generator in normal operation?
Which energy conversion best describes an electric generator in normal operation?
Tap to reveal answer
Kinetic (mechanical) energy $\rightarrow$ electrical energy. Generators use motion to induce electrical current.
Kinetic (mechanical) energy $\rightarrow$ electrical energy. Generators use motion to induce electrical current.
← Didn't Know|Knew It →
Which energy conversion best describes a solar cell (photovoltaic cell)?
Which energy conversion best describes a solar cell (photovoltaic cell)?
Tap to reveal answer
Radiant (light) energy $\rightarrow$ electrical energy. Photons excite electrons to create current.
Radiant (light) energy $\rightarrow$ electrical energy. Photons excite electrons to create current.
← Didn't Know|Knew It →
State the percent efficiency formula for an energy conversion process.
State the percent efficiency formula for an energy conversion process.
Tap to reveal answer
$%\text{efficiency}=\frac{\text{useful output}}{\text{total input}}\times 100%$. Multiply efficiency ratio by 100 to express as percentage.
$%\text{efficiency}=\frac{\text{useful output}}{\text{total input}}\times 100%$. Multiply efficiency ratio by 100 to express as percentage.
← Didn't Know|Knew It →