P2d: Fuels for power

Question 1

Advantages of burning fossil fuels (3)

Answer 1

produces large amounts of elecricity per unit mass

relatively inexpensive

established, reliable technology

Question 2

Disadvantages of burning fossil fuels (4)

Answer 2

releases pollutants into atmo: CO2, global warming; SO2 which can form acid rain

have to be mined and transported, which can have negative impacts on env

non-renewable/finite energy resource; takes long time for fossil fuels to form; we are using them far more quickly than

they are being replenished; they will eventually run out
power plants cause visual pollution

Question 3

Advantages of burning biomass (3)

Answer 3

renewable energy resource; can quickly make more by growing +plants/rearing +animals

uses products which might otherwise be wasted, so fuel costs are very low

carbon neutral: releases CO2 but unlike fossil fuels, no overall + in CO2 as amount released = amount absorbed by plant while it was alive

Question 4

Disadvantages of burning biomass (2)

Answer 4

in developing countries, land for food crops now being used to grow biofuel crops, leading to food shortages

power plants cause visual pollution

Question 5

What are fuels evaluated based on(6)

Answer 5

availability, ease of extraction, pollution, risks, transport, usability

Question 6

Power rating of an appliance equation

Answer 6

power (watts/kilowatts) = voltage x current

Question 7

Equation to calculate the amount of electrical energy supplied

Answer 7

energy supplied (kWh) = power (kW) * time (h)

Question 8

Equation to calculate the cost of electrical energy supplied

Answer 8

cost = energy transferred (kWh) * cost per unit (p/kWh)

Question 9

What is the unit for energy supplied

Answer 9

kilowatt hours

Question 10

Advantages of using off-peak electricity in the home (for consumers and producers) (2)

Answer 10

cost-effective for the electricity
-power stations cannot be turned off at night so
it’s good if there’s a demand for electricity at night

cheaper for consumers if they buy electricity during off-peak hours

Question 11

Disadvantages of using off-peak electricity in the home (for consumers and producers) (2)

Answer 11

slightly increased risk of fire w/ more appliances on at night but no one watching

inconvenient time to use electricity appliances at night

Question 12

Why are transformers used in the National Grid to increase the voltage? (3)

Answer 12

electrical energy is transmitted at high voltage because for a given power transmission & resistance, voltage is inversely
proportional to current so an increased voltage reduces current
-higher current means the hotter the wire
-increasing the voltage therefore decreases energy waste and saves money by reducing heating effect of cables