According to the statements' of the question, pnor"to the inclusion ofR2in
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( the circui~ the current through the two resistances then in the circuit and
connected in series was 50~ and maintained by an e.m.fof 12V. Therefore~ it follows from Ohm's low that
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50 |
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10-3 |
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..L |
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= |
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2Rl |
:n |
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RI |
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.w:n |
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200 |
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50 |
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'j'. ' |
,Rz is connected in parallel as shown, the current in the, cirqJit increases to
62.SinA, which means that the total resistance in the circuit iS,now by Ohm's law
RT= '2 = 320
62.S x 10.3'
It f'OlIows therefore, the parallel combmation ofR} and R2 will have a re~istance
of(32 - 20).0 or 12n. Therefore, ,

,R2 = 240 0 = 300 8
, The, current through R2 is readily computed from the current divider rule as
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IR2 |
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2Q.. |
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62.SA |
= |
25mA |
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50 |
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IR2 = |
25mA |
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(b)', As thoroughly calculated in part (a), R2 = 200
This question was basic electrical theory associated with resistors in circuits when connected in series/parallel. The question seemed quite unpopular with the candidates, with the perfonnance very poor.
, The poor performance was not unconnected with inadequate preparation instead of full coverage of the syllabus.