A-LevelPhysicsElectric fields9702/41 · Oct/Nov 2017 · Q58 Marks

State Coulomb's law for the force between two point charges.

(a)(i)State Coulomb's law for the force between two point charges.[1]
(a)(ii)Two point charges are situated in a vacuum and separated by a distance R. The force between the charges is F_C. On Fig. 5.1, sketch a graph to show the variation of the force F between the charges with separation x for values of x from x = R to x = 4R. [Figure 5.1][3]
(b)Two coils C and D are placed close to one another, as shown in Fig. 5.2. [Figure 5.2] The variation with time t of the current I in coil C is shown in Fig. 5.3. [Figure 5.3] On Fig. 5.4, show the variation with time t of the e.m.f. E induced in coil D for time t = 0 to time t = t₅. [Figure 5.4][4]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.

[A1] force proportional to product of charges and inversely proportional to square of separation
[B1] curve starting at (R, F_C)
[B1] passing through (2R, 0.25F_C)
[B1] passing through (4R, 0.06F_C)
[B1] graph: E = 0 when current constant (0 to t₁, t₂ to t₃, t₄ to t₅)
[B1] stepped from t₁ to t₂ and t₃ to t₄
[B1] (steps) in opposite directions
[B1] later one larger in magnitude

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.