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DFCCIL Executive Electrical 2018 Official Paper

Option 4 : 1,143 Ω

CT 1: Current Affairs (Government Policies and Schemes)

54560

10 Questions
10 Marks
10 Mins

__Concept:__

**Resistance**: The property by which an electric conductor opposes the flow of current through it is called the resistance of the conductor.

It is denoted by R.

The SI unit of resistance is Ohm (Ω).

\(R = \frac{{ρ \;l}}{A}\)

Where ρ is the resistivity of a conductor, l is the length of the conductor and A is the cross-sectional area.

**Calculation:**

When the cable is 700 m long, the resistance of the connected loop is found to be 100 Ω.

Let,

l_{1} = 700 m

R_{1} = 100 Ω

For 8 km long cable,

l_{2} = 8 km = 8000 m

From the above concept,

\(R∝ l\)

∴ 100 Ω ∝ 700 m .... (1)

R_{2} ∝ 8000 m .... (2)

From equation (1) and (2),

\(\frac{R_2}{100}=\frac{8000}{700}\)

**R _{2} = 1,143 Ω**