Alternative B
Question 3B
Observation
Part (a) This was a popular question among the candidates. Many candidates attempted the question and performed well.
(b) Candidates response was fair.
Candidates were expected to:
- measure and record the value of XY to at least 1 d.p in cm.
- read and record the values of Io to at least 1 d.p in A
- read and record the values of Vo to at least 3 d.p in volt
- record six values of R in ohms
- read and record six values of I to at least 1 d.p. in A and in trend
- read and record six values of V to at least 1 d.p. in V and in trend
- show composite table containing at least R, V and I
- Both axes correctly distinguished
- plot a graph using reasonable scales
- draw line of best fit
- determine the slope of the graph
- state any two of the following precautions.
e.g.
- Ensured clean terminals.
- Ensured tight connections.
- Key removed when readings were not taken
- Avoided error of parallax when reading ammeter/voltmeter
- Noted/Avoided zero error when reading ammeter/voltmeter
- Repeated readings shown on table.
b(i) Ohm’s law
Provided the temperature is constant, the current passing through a metallic conductor (wire) is directly proportional to the potential difference across its ends