Question

Four wires of same material, the same cross-sectional area and the same length when connected in parallel give a resistance of 25Ω. If the same four wires are connected in series the effective resistance will be.
(a) 2Ω(b) 4Ω(c) 3Ω(d) 1Ω

ANswer with proper explanation.

Answer 1

Answer: 400 ohm

Explanation:

Given that,

Four wires of same material, the same cross-section area and the same length .

So, resistance of each wire is R

Equivalent resistance in parallel $R_{eq} = 25 \Omega$

Now, four wires is connected in parallel

$\dfrac{1}{R_{eq}} = \dfrac{1}{R_{1}} +\dfrac{1}{R_{2}} +\dfrac{1}{R_{3}} +\dfrac{1}{R_{4}}$

$\dfrac{1}{R_{eq}} = \dfrac{1}{R} +\dfrac{1}{R} +\dfrac{1}{R} +\dfrac{1}{R}$

$\dfrac{1}{25} = \dfrac{4}{R}$

$R = 100\ \Omega$

So, resistance of each wire is 100 ohm

Now, four wires is connected in series then,

The equivalent resistance

$R_{eq} = R_{1} +R_{2} +R_{3} +R_{4}$

$R_{eq} = 100\Omega +100\Omega +100\Omega +100\Omega$

$R_{eq} = 400\Omega$

Hence, the equivalent resistance in series will be 400 ohm.

Answer 2

Answer:

Answer is 400 ohm

Explanation:

hope this helps