Question

Manu connected 4 resistors of equal resistance in parallel to get an effective resistance of 7 ohm. Then what will be the resistance of one resistor?
a).11 ohm
b).4 ohm
c).7 ohm
d). 28 ohm​

Answer 1

Answer:

option D is the correct answer

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Answer 2

Given,

Number of resistors = 4

They have equal resistances.

Their effective resistance = 7 ohm

They are connected in parallel.

To find,

The resistance of one resistor.

Solution,

We can simply solve this numerical problem by using the following process.

Let, the resistance of each resistor = x ohm

As they are connected in parallel, their effective resistance (r) will be :

$\frac{1}{r} = (\frac{1}{x} + \frac{1}{x} + \frac{1}{x} + \frac{1}{x})ohm$

$\frac{1}{r} = \frac{4}{x} \: \: ohm$

$r = \frac{x}{4} \: \: ohm$

According to the data mentioned in the question,

$\frac{x}{4} = 7$

$x = 7 \times 4 = 28 \: \: ohm$

(This will be considered as the final result.)

Hence, resistance of one resistor is 28 ohm (option D).