Kevin wants to use less fossil fuel by purchasing an electric vehicle. EV’s are currently about 50% efficient. The power in Kevin’s neighborhood comes from a coal-fired power plant. When Kevin plugs his EV in at night, what is powering his car?

Question

Kevin wants to use less fossil fuel by purchasing an electric vehicle.  EV’s are currently about 50% efficient. The power in Kevin’s neighborhood comes from a coal-fired power plant.  When Kevin plugs his EV in at night, what is powering his car?

BlackTom AI · Accepted Answer

Electric vehicles run on electricity supplied by the grid; if the grid’s generation in Kevin’s neighborhood comes from a coal-fired power plant, the ultimate energy source powering his car is coal.

1) Relevant knowledge points
- Energy source and energy carrier: coal (chemical energy) is burned to make heat, which drives turbines to produce electricity (the grid). Electricity is the carrier delivered to homes.
- Conversion steps and efficiencies: thermal-to-electric conversion at a coal plant, transmission/distribution losses, charger/battery and drivetrain efficiencies in an EV. The given statement that EVs are about 50% efficient refers to the fraction of delivered electrical energy that becomes useful propulsion energy (well‑to‑wheel efficiency will be lower when generation losses are included).

2) Step-by-step reasoning
- Kevin plugs his EV into the neighborhood grid at night.
- The grid supplies electricity produced by the local coal-fired plant.
- That electricity travels through the transmission and distribution system to his home outlet, then through his charger into the battery and drivetrain to move the car.

3) Example calculation (illustrative)
- Start with 1.00 unit of chemical energy in coal.
- Coal plant electrical efficiency (example) ≈ 35% → 1.00 × 0.35 = 0.35 units of electricity generated.
- Transmission/distribution losses (example) ≈ 6% → 0.35 × 0.94 = 0.329 units delivered to the home.
- EV conversion to motion (given) ≈ 50% → 0.329 × 0.50 = 0.1645 units of mechanical work at the wheels.
This shows most of the original energy originated in coal; the chain begins with coal combustion.

4) Why "Coal" is correct
Because the grid electricity Kevin uses is produced by a coal-fired plant, the primary fuel source powering his EV (even indirectly through conversion steps) is coal.

5) Why other plausible answers would be incorrect
- Gasoline: incorrect because an EV does not burn gasoline; a gasoline car would be powered by gasoline.
- Solar/wind/nuclear: incorrect here because the problem statement specifies the neighborhood power comes from a coal-fired plant, not renewables or nuclear.
- Battery alone: the battery stores energy but does not create it; its energy came from coal-generated electricity.

Conclusion: Given the neighborhood electricity source is coal-fired generation, the correct answer is Coal. This matches the provided answer.

Kevin wants to use less fossil fuel by purchasing an electric vehicle. EV’s are currently about 50% efficient. The power in Kevin’s neighborhood comes from a coal-fired power plant. When Kevin plugs his EV in at night, what is powering his car?单项选择题

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