What are the three main stages electricity passes through between a power station and a home?

Generation → storage → metering Generation → high-voltage transmission → lower-voltage distribution Compression → inversion → regulation Switching → buffering → conditioning

Why is electricity transmitted at very high voltages (e.g., 400,000 V) over long distances rather than at the 230 V used in homes?

High voltage allows thinner, lighter cables because the electrons travel faster High voltage prevents the cables from overheating by repelling heat radiation High voltage reduces current for the same power, and since losses = I²R, lower current dramatically reduces resistive heating in the cables High voltage is required by regulators to reduce electromagnetic interference with radio signals

A power line transmits 500 MW at 400 kV. What is the current in the line?

125 A 1,250 A 12,500 A 125,000 A

How does a transformer step voltage up or down?

By accelerating electrons through an electric field between two charged plates By converting AC to DC and back at different voltages using a rectifier and inverter By electromagnetic induction between two coils with different numbers of turns wound on a shared iron core; V₁/V₂ = N₁/N₂ By using a variable resistor to drop voltage across the primary coil

A transformer has 2,000 turns on its primary coil and 100 turns on its secondary coil. If the primary voltage is 10,000 V, what is the secondary voltage?

50 V 500 V 5,000 V 200,000 V

Why are transformers used in AC grids but NOT suitable for DC transmission at fixed voltage levels?

DC current is too high for transformers to handle without overheating Transformers require magnetic cores that only work with the 50/60 Hz frequency of AC Transformers rely on a changing magnetic flux, which DC (constant current) does not produce — no changing flux means no induced EMF in the secondary coil DC power is always transmitted at the voltage it is generated at, so no transformation is needed

Modern HVDC (High Voltage Direct Current) transmission is preferred over HVAC for very long submarine cable links. What is the main reason?

DC cannot be transformed to higher voltages, so lower voltages are used, reducing cable insulation requirements DC lines are cheaper to build because they need only two conductors instead of three Long AC submarine cables have large capacitive charging currents that consume capacity and cause losses; DC eliminates this problem Seawater conducts electricity, interfering with AC signals but not DC

A smart grid differs from a traditional grid primarily because it includes:

Underground cables instead of overhead pylons, reducing storm damage Two-way digital communication between utilities and consumers, enabling real-time monitoring, demand response, and integration of distributed generation Larger transformers that can handle higher current surges during storms Backup diesel generators at every substation to prevent blackouts

Energy intensity of an economy is defined as energy consumed per unit of GDP. A country with falling energy intensity is most accurately described as:

Reducing its total energy consumption year on year Switching from fossil fuels to renewable sources Producing more economic output per unit of energy — becoming more energy-efficient Exporting more energy than it imports

Global primary energy consumption is currently supplied approximately 80% by fossil fuels. What does 'primary energy' mean?

The electricity generated by the most important power stations in a country Energy from the first power stations built in each country The total energy extracted from natural resources before any conversion or transformation losses The energy consumed by industrial processes, excluding households

The 'duck curve' is a challenge facing electricity grids with high solar penetration. What does it describe?

The characteristic shape of wind turbine power output plotted against wind speed A large midday solar generation surplus that suppresses prices, followed by a steep evening ramp-up when solar drops but demand peaks The shape of a transmission cable that hangs in a catenary curve between pylons The declining cost curve of solar panels over time

Demand-side management (DSM) is an important tool for smart grid operators. What does it involve?

Installing demand metres at every home to measure electricity consumption more accurately Reducing total national electricity demand by mandating more efficient appliances Encouraging or automatically shifting consumer electricity use (e.g., EV charging, washing machines) to times when generation is abundant and prices are low Controlling the supply voltage to consumers during periods of high network loading