Part (a): This was not a popular question among the candidates probably due to the fact that most schools could not afford to two sets of resistance boxes for each set-up. However, the few responding candidates performed averagely. The determination of y = 
was not correctly evaluated.
Part (b): Many candidates gave good responses.
In part (a), candidates are expected to:
- Measure and record Emf of battery to at least 1 d.p in volts.
- Measure and record Vo to at least 1 d.p in volts.
- Record five values of R in ohms.
- Read and record five values of V1 to at least 1 d.p in volts and in trend.
(Trend: As R increases, V1 decreases)
- Show composite table containing R, V1 and V1-1
- Plot a graph using reasonable scales
- Draw line of best fit
- Determine the slope of the graph
- Evaluate y =
State any two of the following precautions:
e.g - Key removed when not taking readings
- Ensured tight/clean terminal
- Avoided parallax error in reading voltmeter
- Noted and corrected/avoided zero error on the voltmeter
- Repeated readings shown on table.
In part (b), the expected answers are:
(i) The potential difference (in volts) between two points in a circuit is the
work done (in joules) when one unit of positive charge (coulomb) moves from
one point to the other
E = IR + Ir
3 = 0.5 x 4 + 0.5r
3 = 2 + 0.5r
r = 3 - 2
0.5
= 2Ω
.