Question : A wire of resistance R is melted and recast to half of its length, then the new resistance of the wire will be
Option 1: R/4
Option 2: R/2
Option 3: R
Option 4: 2R
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Correct Answer: R/4
Solution : The correct option is R/4.
When a wire is melted and recast to half of its original length, its resistance will change. The resistance of a wire is directly proportional to its length. The formula for resistance (R) is:
R = ρ*(L/A)
Where:
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Question : A wire of resistance R is cut into 'n' equal parts. These parts are then connected in parallel. The equivalent resistance of the combination will be
Option 1: nR
Option 2: R/n
Option 3: n/R
Option 4: R/n2
Question : A rod of 5 cm radius and 52 cm length is converted into a wire of 100 cm length of uniform thickness. The radius of the wire (in cm) is:
Option 1: $\sqrt{13}$
Option 2: $\sqrt{15}$
Option 3: $\sqrt{23}$
Option 4: $\sqrt{17}$
Question : A metallic sphere of radius 21 cm is melted and then recast into smaller cones, each with a 7 cm radius and a height of 3 cm. Find the number of cones obtained.
Option 1: 225
Option 2: 325
Option 3: 522
Option 4: 252
Question : The length of a cuboid is 8 cm. If the breadth of the cuboid is twice its length and the height of the cuboid is half of its length, then what is the total surface area of the cuboid?
Option 1: $448 \ \text{cm}^2$
Option 2: $216 \ \text{cm}^2$
Option 3: $188\ \text{cm}^2$
Option 4: $154\ \text{cm}^2$
Question : The sum of the length and breadth of a cuboid is 4 cm. Length is three times the breadth. If the height of the cuboid is half of the sum of its length and breadth. Then what is the total surface area of the cuboid?
Option 1: 64 cm2
Option 2: 22 cm2
Option 3: 32 cm2
Option 4: 30 cm2
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