The resistance of a copper wire 200 m long is 21 $$\Omega .$$ If its thickness (diameter) is 0.44 mm, its specific resistance is around

Two monochromatic waves having frequencies $$\omega $$ and $$\omega + \Delta \omega \left( {\Delta \omega \ll \omega } \right)$$ and corresponding wavelengths $$\lambda $$ and $$\lambda - \Delta \lambda \left( {\Delta \lambda \ll \lambda } \right)$$ of same polarization, travelling along X-axis are superimposed on each other. The phase velocity and group velocity of the resultant wave are respectively given by

A

$$\frac{{\omega \lambda }}{{2\pi }},\,\frac{{\Delta \omega {\lambda ^2}}}{{2\pi \Delta \lambda }}$$

B

$$\omega \lambda ,\,\frac{{\Delta \omega {\lambda ^2}}}{{\Delta \lambda }}$$

C

$$\frac{{\omega \Delta \lambda }}{{2\pi }},\,\frac{{\Delta \omega \Delta \lambda }}{{2\pi }}$$

D

$$\omega \Delta \lambda ,\,\omega \Delta \lambda $$

When the main switch of the house is put off it disconnects the: (A) Live wire only (B) Live wire and the earth wire (C) Live wire and the neutral wire (D) Earth wire and the neutral wire

A

B

A

C

D

C

If 30Ω6 = -5, 80Ω2 = -40 and 20Ω4 = -5, then find the value of 70Ω2 = ?

A

10

B

-35

C

15

D

-20

If 7Ω6 = 84, 8Ω7 = 112 and 8Ω4 = 64, then find the value of 3Ω4 = ?

A

24 \

B

12 \

C

4 \

D

20

If 7Ω6 = 84, 8Ω7 = 112 and 8Ω4 = 64, then find the value of 3Ω4 = ?

A

24 \

B

12

C

4 \

D

20

The raised cosine pulse p(t) is used for zero ISI in digital communications. The expression for p(t) with unity roll-off factor is given by $$p\left( t \right) = \frac{{\sin 4\pi \omega t}}{{4\pi \omega t\left( {1 - 16{\omega ^2}{t^2}} \right)}}.$$ The value of p(t) at $$t = \frac{1}{{4\omega }}$$ is

A

-0.5

B

0

C

0.5

D

∞

For a function g(t), it is given that
$$\int\limits_{ - \infty }^{ + \infty } {g\left( t \right){e^{ - j\omega t}}dt = \omega {e^{ - 2{\omega ^2}}}} $$ for any real value $$\omega $$ . If $$y\left( t \right) = \int\limits_{ - \infty }^t {g\left( \tau \right)} d\tau ,\,{\rm{then}}\,\int\limits_{ - \infty }^{ + \infty } {y\left( t \right)} dt$$ is. . . . . . . .

A

0

B

-j

C

$$ - {j \over 2}$$

D

$${j \over 2}$$

The Fourier transform of a signal
h(t) is $$H\left( {j\omega } \right) = {{\left( {2\cos \omega } \right)\left( {\sin \omega } \right)} \over \omega }$$
The value of h(0) is

A

$${1 \over 4}$$

B

$${1 \over 2}$$

C

1

D

2

Let us consider a copper wire having radius r and length l. Let its resistance be R. If the radius of another copper wire is 2r and the length is $$\frac{l}{2}$$, then the resistance of this wire will be

A

R

B

2R

C

$$\frac{R}{4}$$

D

$$\frac{R}{8}$$

There are two wires of same material and same length while the diameter of second wire is two times the diameter of first wire, then the ratio of extension the diameter of first wire, then the ratio of extension produced in the wire by applying same load will be _____________

A

1:1

B

2:1

C

1:2

D

4:1

The resistance of a copper wire 200 m long is 21 $$\Omega .$$ If its thickness (diameter) is 0.44 mm, its specific resistance is around

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