Question 22M.2.SL.TZ1.4c.i
| Date | May 2022 | Marks available | [Maximum mark: 3] | Reference code | 22M.2.SL.TZ1.4c.i |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Deduce | Question number | c.i | Adapted from | N/A |
A power supply is connected to three resistors P, Q and R of fixed value and to an ideal voltmeter. A variable resistor S, formed from a solid cylinder of conducting putty, is also connected in the circuit. Conducting putty is a material that can be moulded so that the resistance of S can be changed by re-shaping it.
The resistance values of P, Q and R are 40 Ω, 16 Ω and 60 Ω respectively. The emf of the power supply is 6.0 V and its internal resistance is negligible.
All the putty is reshaped into a solid cylinder that is four times longer than the original length.
Deduce the resistance of this new cylinder when it has been reshaped.
[3]
recognition that leads to / «» = ✓
«because the volume of S is constant new area is» ✓
16 x 24 = 384 «Ω» ✓
Most candidates recognized that increasing the length of the conductive putty would increase the resistance by a factor of four, but very few considered that if the volume of the putty remained constant that the cross-sectional surface area would decrease as well.
