Basic Electricity 3, May/June 2015

Question 1

AIM: To determine the relationship between current and voltage in series circuit.

(a) Connect the circuit diagram as shown in figure 1.

(b) Ask the supervisor to check the circuit connection.

(c) Copy Table 1 in the answer booklet.  

Table 1


Source voltage
(V)

Ammeter reading
           (mA)               

Voltmeter reading
            (V)

0

 

 

2

 

 

4

 

 

8

 

 

8

 

 

10

 

 

(d) Set the variable power supply unit to 0V.

(e) Close the switch (S).

(f) Read and record in Table 1, the corresponding ammeter and voltmeter readings.

(g) Adjust the power supply unit to 2V, 4V, 6V, 8V and 10V. Repeat the step (f) at each setting.

(h) Plot the graph of voltmeter (V) readings on the vertical axis against the ammeter (mA) readings on the horizontal axis

. (i) Calculate the slope of the graph.

(j) Which law does the relationship in step (i) obey?  

Observation

The expected answers were:

(a)  

                                                                Table 1


Source voltage
(V)

Ammeter reading
(mA)

Voltmeter reading
           (V)

0

0.00

          0.00

2

138.12

          1.99

4

276.23

          3.97

6

414.35

          5.96

8

552.47

          7.95

10

690.58

          9.94

(b) Correct reading of both ammeter and voltmeter

(c) Correct axes (x,y and origin)

(d) Reasonable scale and title

(e) Plotting of points

(f) Line of best fit (one having scattered points very well

(g) Slope of graph (A linear graph)

(h) Relationship obeys Ohm's law

Candidates were required to determine the relationship between current and voltage in a series circuit.


The candidates, as reported, understood the question and carried out the task required. But some of the candidates did not record accurate voltage and current readings.