Write any two examples of fossil fuels.

State the two forms in which energy is mainly utilised in our homes.

The main constituent of biogas is

The energy liberated by burning $1 \,g$ of charcoal is approximately: (in $,kJ$)

$(i)$ Write the value of the solar constant of the Sun.
$(ii)$ What type of mirror is used in a box-type solar cooker?
$(iii)$ Why is it difficult to use hydrogen as a source of energy?
$(iv)$ What is the maximum temperature attained in a concave reflector-type solar cooker?
$(v)$ Fossil fuels are classified as a non-renewable source of energy. Explain why.

The use of dry wood as domestic fuel is not considered good. State two reasons for it.