Use these questions to test your understanding. If you get them wrong, you will be linked back to the relevant part of the notes. 

Be sure you study them thoroughly (don't just get a quick fix for your mistake) so your overall understanding is improved.

1. The Sun has been able to produce energy for billions of years by

    a. a chemical process similar to burning coal          b. gravitational contraction         c. absorbing light from distant stars

    d. nuclear fusion        e. none of the above

2. The Sun's output is so stable because

    a. pressure of Sun's gas just balances gravitational contraction

    b. the Sun is so old

    c. the Sun doesn't produce much energy

    d. the Sun rotates

    e. the Sun has only small sunspots

3. Although deep inside the sun, energy is carried by photon streaming, energy is carried to the surface of the sun

    a. by conduction

    b. also by photon streaming

    c. by convection, like boiling

    d. by magnetism

    e. by sunspots

a. because trace elements are required              b. because the temperature and pressure are too low

c. because the hydrogen needs other isotopes             d. because an electric spark is needed

e. it will become helium if you wait long enough