How does the resistance of a place of conducting wire change if both its length

Question

How does the resistance of a place of conducting wire change if both its length and diameter are doubled? Remains the same increase 2 times Decreases 2 times Increases 4 times Decreases 4 times If you test 12 V battery in your car and you measure voltage on the terminals of the battery: The difference of potential between the battery's terminals will always be 12 V and will not depend on the current flowing through the external load resistance (otherwise, why should we even call it 12 V battery 1?) The voltage will increase when we reduce the resistance of the external resistor. The voltage will decreases when we allow larger current to flow. The voltage on terminals of the battery will change sign if we swap the ends of the resistor.

Explanation / Answer

1)
The electrical resistance of a wire is given by
R = (p * L)/A
If we Double the Length & Diameter
R' = (p * 2*L)/(4*A)
R' = 1/2 *  (p * L)/A
R' = 1/2*R
Correct option - Decreases 2 times.

2)
The voltage will allways remain 12 V Across battery !!
Corect Option :- (a)

3)
In Series,
Req = R1 + R2
So if we want to double Connect them in series.

Corect Option :- (a)

4)
In Parallel,
Same Voltage is applied in case of parallel connection therefore Total Power exhausted in Bulb = 60 + 60 = 120 W

In Series, Same current flows through each Bulb, but voltage will be different !!

So Corect Option :- (b)


5)
The connection is in parallel, or else no bulb would have shined if any one is burnt.
Corect Option :- (b)

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