Applied Electricity 1, Nov/Dec 2010
 Questions: 1 2 Main
General Comments
Weakness/Remedies
Strength

Question 1

AIM: To verify Kirchhoff's Current law

(a) Connect the circuit as shown in Fig.1.
(b) Ask the Supervisor to check the circuit connection.
(c) Copy Table 1 into your answer booklet.
Table 1

 11(mA) 12(mA) 13 (mA) 11 + 12 (mA)

(d)Close switch S.
(e)Set the power supply to 12 V.
(f) Read and record the values of A1.A2 and A3 into Table 1.
(g)Compare the values of 11 + 12 with that of 13
(h)Comment on the answer obtained in (g).

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Observation

The candidates were required to:
(i) connect the circuit as shown and take ammeter readings;
(ii) compare on the values of the currents entering a node and that leaving;
(iii) comment on the answer obtained in (g).
The expected answers were:
Table 1

 11(mA) 12(mA) 13 (mA) 11 + 12 (mA) 0.222 0.025 0.252 0.247

(g) On comparing the values of 11 + 12 with that of 13, the two are the same or 11 + 12 = 13.
(h) This confirms Kirchhoff's Current Law (which states that the algebraic sum of current into any junction is zero).
From the results obtained, the addition of the currents entering into a node is equal the current going out of the node which is in consonance with Kirchhoff's Current Law.
The candidates undertook the task by connecting the circuit using the components provided and current through each ammeter. Their inability to obtain correct measurements using the measuring instruments was their undoing

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