Question

CURRENT ELECTRICITY
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16.A wire of resistance 12 ohms per meter is bent 19. A
to form a complete circle of radius 10 cm. The
resistance between its two diametrically
opposite points, A and B as shown in the figure,
is:
[AIPMT 2009]
b
SY
р-
A
-В

Answer 1

Answer:

12 ohm resistance per unit meter means in 1 m wire 12 ohm resistance present

total length of the wire= circumference of circle , length =2πr, L= 2π×0.1 , here r is 10 cm (0.1m) so total L is 0.2π , total resistance in length = 0.2π×12, total R= 2.4π . opposite point A and B present in diametrically and they divide the length of the wire half so resistance also divide half -half then one resistor is 1.2π and another is also 1.2π and both present in parallel combination so 1/Req= 1/1.2π+1/1.2π ,1/Req=2/1.2π then Req is 0.6π ans

Answer 2

Answer:

The radius of the circle is 10 cm. =r

So the perimeter of the semi(half) circle (A to B)

Is = (pi) *r = (pi) *10 cm = 0.1 *(pi) meter.

So resistant of this wire is = 12 *{0.1*(pi)} =1.2 *(pi) ohm.

Now 2 wire is in parallel combination with equal resistance.

So if total resistance is R then

$\frac{1}{ R} = \frac{1}{1.2\pi} + \frac{1}{1.2\pi}$

Or R= 1.2π/2 =0.6π ohm

So option 2 is correct