Question EXE.2.SL.TZ0.6
| Date | Example questions Example questions | Marks available | [Maximum mark: 8] | Reference code | EXE.2.SL.TZ0.6 |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Calculate, Explain, Show that | Question number | 6 | Adapted from | N/A |
A rod is formed from two metal rods XY and YZ of identical dimensions. End X and end Z are at different temperatures.
The side of the rod can be unlagged or ideally lagged. Explain the difference in energy transfer for these two cases.
[3]
When ideally lagged, no energy transfer can occur through the sides of the bar. ✓
All the power input/ energy input per second at one end will emerge at the other end. ✓
When unlagged, energy transfer occurs from the sides of the bar and the power /energy input per second at input > the energy output per second at the other end. ✓
Max 1 if answer does not refer to rate of energy transfer in MP2 and MP3.
Rod XYZ is ideally lagged. The thermal conductivity of XY is k and the thermal conductivity of YZ is 2k. End X is at 90 °C and end Z is at 45 °C
Calculate the temperature at Y.
[3]
idea that is same in both bars because lagged ✓
work to show that
OR
Temperature difference across XY is twice temperature difference across YZ ✓
solves to show that ✓
The temperatures are now reversed so that X is at 45 °C and Z is at 90 °C. Show that the rate of energy transfer is unchanged.
[2]
repeats calculation to show that θ = 75 °C ✓
temperature difference across YZ is still 15 K which gives the same rate of energy transfer (but in opposite direction) ✓