Question 19M.3.hl.TZ1.a
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.3.hl.TZ1.a |
| Level | hl | Paper | 3 | Time zone | TZ1 |
| Command term | Compare | Question number | a | Adapted from | N/A |
This question is about solar cells.
Some solar cells use photovoltaic semi-conductors. Compare, giving reasons, the electrical conductivity of metals and semi-conductors as temperature increases.
[3]
metal conductivity decreases AND semi-conductor conductivity increases [✔]
metal: collisions between «already free moving» electrons/vibrating lattice ions and electrons increase [✔]
semi-conductor:
provides sufficient energy for electrons to move to conduction band
OR
allows semiconductors to ionize forming freely moving electrons [✔]
Candidates struggled to express themselves adequately in comparing the change in electrical conductivity of metals and semi-conductors as temperature increases. Many scored 1 mark for stating the effect of increasing temperature, but very few scored any marks for the explanation.
