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Show how you would connect three resistors, each of resistance 6, so that the combination has a resistance of (i) 9, and (ii) 4 .

(i) In order to get a resistance of 9 from three resistors of 6 each, we connect two 6 resistors in parallel and then this parallel combination is connected in series with the third 6 resistor .

For parallel connection:

Or R= 3

And for series connection: R= 3 + 6= 9

(ii) In order to get a resistance of 4 from three resistors of 6 each, we connect all the three 6 resistors in parallel:

Or R= 2

Then, Net Resistance R= 2+ 2= 4.

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Several electric bulbs designed to be used on a 220 V electric supply line are rated 10 W each. How many bulbs can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A ?

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