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Resistance in a Parallel Circuit.
The total resistance of a parallel circuit is calculated using the formula
1/R = 1/R1 + 1/R2 + 1/R3 ·····
In the above circuit,
1/R = 1/2 + 1/3 + 1/4
= 6/12 + 4/12 + 3/12
= 13/12
R = 12/13
= 0·92 Ohms.
Notice that this is a much smaller resistance
than you get in the series circuit
using the same
resistors.
It is even
smaller than the smallest
resistor in the parallel circuit,
which is 2 Ohms.
Putting more resistors in the
parallel circuit decreases the total
resistance
because the electricity has
additional branches to flow
along
and so the total
current flowing increases.
Headings Parallel Circuits Electricity Search Questions 
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