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

5. Hydrogen fusion can produce energy because

    a. at the end the electrons in the atoms have gone to lower energy levels and given off the energy they lost

    b. the atoms join together into bigger molecules, and the molecular binding energy is released

    c. the fusion products weigh a little less than the input materials, and the mass that is lost appears as energy

    d. the helium that is produced has been heated to very high temperature

    e. the high pressure where the fusion takes place yields some of its energy