JEE 2016 :: Main 2016 :: Physics 2016

• Main 2016 - Physics 2016
• Main 2016 - Chemistry 2016
• Main 2016 - Mathematics 2016

Arrange the following electromagnetic radiations in the order of increasing energy

A.Blue light    B.Yellow light

C.X-ray          D. Radio wave

Answer:

Explanation:

Theoretical question. Therefore, no solution is required.

An arc lamp requires a direct current of 10A at 80 V to function. If it is connected to a 220V (rms) , 50Hz AC supply, the series inductor needed for it to work is close to 

Answer:

Explanation:

$V^{2}=V_{R}^{2}+V_L^2\Rightarrow 220^{2}=80^{2}+V_L^2$

Solving we get,

   $V_L \approx 205 V$

$X_{L}=\frac{V_{L}}{I}=\frac{205}{10}=20.5$Ω = ω L

$L=\frac{20.5}{2\pi \times50}=0.065 H$

Hysteresis loops for two magnetic materials A and B are as  given below

These materials are used to make magnets for electric generators, transformer core, and electromagnet core. Then, it is proper to use

Answer:

Explanation:

We need high retentivity and high coercivity for electromagnets and a small area of hysteresis loop for transformers.

Two identical wires A and B, each of length l, carry the same current I. Wire A is bent into a circle of radius R and wire B is bent to form a square of side a. If B_A and B_B are the values of the magnetic field at the centers of the circle and square respectively. then the ratio $\frac{B_{A}}{B_{B}}$ is

Answer:

Explanation:

B at centre of a circle =  $\frac{\mu_{0}I}{2R}$

B at centre of a square 

     $=4\times \frac{\mu I}{4\pi.\frac{l}{2}}[\sin 45 ^{\circ} + \sin 45 ^{\circ}]$

     $=4\sqrt{2}\frac{\mu I}{2\pi l}$

Now, $R=\frac{L}{2\pi} $   and   $l= \frac{L}{4}$

                                                                 (As L=$2\pi R= 4l$ )

 Where , L= length of wire

   $B_{A}=\frac{\mu_{0}I}{2.\frac{L}{2\pi}}=\frac{\pi\mu_{0}I}{L}=\pi [\frac{\mu_{0}I}{L}]$

  $B_{B}=4\sqrt{2}\frac{\mu_{0}I}{2\pi(\frac{L}{4})}$

$=\frac{8\sqrt{2}\mu_{0}I}{\pi L}=\frac{8\sqrt{2}}{\pi}[\frac{\mu_{0}I}{L}]$

    $\frac{B_{A}}{B_{B}}=\pi^{2}:8\sqrt{2}$

The temperature dependence of resistance of Cu and undoped Si in the temperature range 300-400 K, is best described by

Answer:

Explanation:

As we know CU is a conductor , so an increase in temperature, resistance will increases. Then, Si semiconductor, so with increases in temperature, resistance will decreases

• Main 2016 - Physics 2016
• Main 2016 - Chemistry 2016
• Main 2016 - Mathematics 2016