Question 21N.2.HL.TZ0.3
| Date | November 2021 | Marks available | [Maximum mark: 11] | Reference code | 21N.2.HL.TZ0.3 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Calculate, Determine, Draw, Explain, Show that, State | Question number | 3 | Adapted from | N/A |
Two equal positive fixed point charges Q = +44 μC and point P are at the vertices of an equilateral triangle of side 0.48 m.
Point P is now moved closer to the charges.
A point charge q = −2.0 μC and mass 0.25 kg is placed at P. When x is small compared to d, the magnitude of the net force on q is F ≈ 115x.
An uncharged parallel plate capacitor C is connected to a cell of emf 12 V, a resistor R and another resistor of resistance 20 MΩ.
Show that the magnitude of the resultant electric field at P is 3 MN C−1
[2]
«electric field at P from one charge is »
OR
«NC−1» ✓
« net field is » «NC−1» ✓
State the direction of the resultant electric field at P.
[1]
directed vertically up «on plane of the page» ✓
Allow an arrow pointing up on the diagram.
Explain why q will perform simple harmonic oscillations when it is released.
[2]
force «on q» is proportional to the displacement ✓
and opposite to the displacement / directed towards equilibrium ✓
Calculate the period of oscillations of q.
[2]
✓
✓
Award [2] marks for a bald correct answer.
Allow ECF for MP2.
At t = 0, the switch is connected to X. On the axes, draw a sketch graph to show the variation with time of the voltage VR across R.
[2]
decreasing from 12 ✓
correct shape as shown ✓
Do not penalize if the graph does not touch the t axis.
The switch is then connected to Y and C discharges through the 20 MΩ resistor. The voltage Vc drops to 50 % of its initial value in 5.0 s. Determine the capacitance of C.
[2]
✓
«F» ✓
Award [2] for a bald correct answer.