Question 19M.2.HL.TZ1.b.ii
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.HL.TZ1.b.ii |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Explain | Question number | b.ii | Adapted from | N/A |
A student makes a parallel-plate capacitor of capacitance 68 nF from aluminium foil and plastic film by inserting one sheet of plastic film between two sheets of aluminium foil.
The aluminium foil and the plastic film are 450 mm wide.
The plastic film has a thickness of 55 μm and a permittivity of 2.5 × 10−11 C2 N–1 m–2.
The student uses a switch to charge and discharge the capacitor using the circuit shown. The ammeter is ideal.
The emf of the battery is 12 V.
The ammeter is replaced by a coil. Explain why there will be an induced emf in the coil while the capacitor is discharging.
[2]
mention of Faraday’s law ✔
indicating that changing current in discharge circuit leads to change in flux in coil/change in magnetic field «and induced emf» ✔
This is an explain question, so there was an expectation for a fairly detailed response. Many candidates missed the fact that the discharging capacitor is causing the current in the coil to change in time, and that this is what is inducing the emf in the coil. Many simply stated that the current created a magnetic field with not complete explanation of induction.
