Question 21M.2.HL.TZ2.d.ii
| Date | May 2021 | Marks available | [Maximum mark: 2] | Reference code | 21M.2.HL.TZ2.d.ii |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Outline | Question number | d.ii | Adapted from | N/A |
A vertical wall carries a uniform positive charge on its surface. This produces a uniform horizontal electric field perpendicular to the wall. A small, positively-charged ball is suspended in equilibrium from the vertical wall by a thread of negligible mass.
The centre of the ball, still carrying a charge of 1.2 × 10−6 C, is now placed 0.40 m from a point charge Q. The charge on the ball acts as a point charge at the centre of the ball.
P is the point on the line joining the charges where the electric field strength is zero. The distance PQ is 0.22 m.
Outline, without calculation, whether or not the electric potential at P is zero.
[2]
work must be done to move a «positive» charge from infinity to P «as both charges are positive»
OR
reference to both potentials positive and added
OR
identifies field as gradient of potential and with zero value ✓
therefore, point P is at a positive / non-zero potential ✓
Award [0] for bald answer that P has non-zero potential
