Or
(a) For the circuit shown in the
given figure,
What is the value of
(i) current through 
resistor?
(ii) potential difference across
resistor?
(b) In an electrical circuit,
three incandescent bulbs A, B and C of rating 40 W 60 W and 100 W respectively
are connected inparallel to an electric source. Write the order of brightness.
Answer:
Here,
and
are connected
in parallel, let their equivalent resistance be R'.
(1)
Now, the given circuit can be redrawn
as
(1)
Now, 
and 
are in
series, let their equivalent resistance be 
Similarly, 
and 
are in
series.
Their equivalent resistance
Now, circuit can be redrawn
Now 
and 
are in
parallel, so equivalent resistance of the circuit.
Total current
(1)
Or
(a) Let the current through the
circuit be 
which is divided
into 
and 
in the alms
AB and CD respectively, then
(1)
In the arm AB, the total
resistance is
(1/2)
and the total resistance in the
arm CD is
(1/2)
(i) Current in 
resistor
Current through CD is
(1)
(ii) Potential
difference across 
resistor
is
(1)
(b) Bulbs are rated presuming
that they all are tobe connected with the same voltage supply (say 230 V in
India). In parallel combination, voltage remains same, so greater the watt,
greater the brightness.
Therefore, brightness (B) of
three bulbs are as follows
(1+1)
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