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Physics Paper 1, MAy/June. 2008  
Questions: 1 2 3 4 5 6 Main

General Comments

Question 6

(a) You are provided with a battery, a resistance box and other necessary apparatus.
(i) Connect a circuit as shown above.

(ii) Set the resistance in the resistance box at Ro = 0 Ω. Read and record the ammeter reading Io

(iii) Evaluate Io­¹.

(iv) Repeat the procedure for five other values of R = 2,3,4 5 and 6Ω
In each case, read and record the ammeter reading I. Also evaluate

(v) Plot a graph of I on the vertical axis against R on the horizontal
(vi) Determine the slope, s, of the graph. Also determine the intercept, c, on the vertical axis.

(vi) Evaluate k = c .

(xi) State two precautions taken to obtain accurate results. [21 marks]

(b) (i) Explain electromotive force of a cell. [2 marks]

(ii) Explain, with the aid of a lebelled diagram, how a galvanometer may be adapted to read as an ammeter. [2 marks]


The candidates were expected to:

(i) set up a circuit diagram as shown in the diagram above;

(ii) read and record the value of Io in ampere to at least 1 decimal place;

(iii) evaluate and record the value of I­¹ to 1 decimal place;

(iv) read and record five values of I in ampere to at least 1 decimal place in trend.
Trend: As R increases, I decreases;

(v) evaluate five values of I­¹ to at least 3 significant figures.

(vi) present data in a composite and complete table and
showing at least I, I­¹ and R;

(vii) correctly distinguish the graph axes , select reasonable scales, plot the five points and draw a line that best fits the points;

(viii) draw a large right angled triangle on the graph line, read Δ I­¹
and ΔR and evaluate slope = Δ I­¹

(ix) show and read the intercept on the vertical axis;

(x) evaluate k = c/s;

(xi) state any two of the following precautions in the correct form of speech:

- I ensured firm support of pendulum;
- Ensured tight connections/clean terminals
- Zero error of ammeter noted and corrected for;
- Parallax error in ammeter avoided.

b (i) The electromotive force of a cell is the work done in driving a unit of electric charge round a complete circuit OR

The electromotive force is the total work done in driving one coulomb of electricity round the circuit OR

The total energy per coulomb obtained from a cell or battery.

(ii) A galvanometer adapted to read as an ammeter.

This experiment was very popular among the candidates. However, some candidates failed to record their initial ammeter reading; record the reciprocal of I to the required decimal places; evaluate k = c/s.

In part b, many candidates failed to explain electromotive force of a cell correctly. Some candidates could not explain with the aid of a labeled diagram how a galvanometer may be adapted to read as an ammeter.

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