In a fair weather condition,there is an electric field at the surface of the earth, pointing down into the ground. What is the electric charge on the ground in this situation?

1

(a)

Electric field lines start from positive charges and end on negative charge.
Thus, if the fair weather field is directed down into the ground, the ground must possess a negative charge.

Two wire of equal length one copper and manganin have same resistance , which wire is thicker?

1

(a)

Resistivity of Copper is less, hence mangain wire is thicker

A Current ‘I’ flows along the length of an infinitely long straight thin walled pipe. What is the magnetic field at any point on the axis of pipe?

1

(a)

Zero

A bar magnet M is dropped so that it falls vertically through the coil C. The graph obtained for voltage produced across the coil vs time is shown in figure (b).
(i) Explain the shape of the graph.
(ii) Why is the negative peak longer than the positive peak?

1

(a)

(i) As magnet approaches the coil the rate of change of magnetic flux increases and the induced emf also increases. As soon as one pole of magnet enters into the coil the emf decreases due to the other pole effect and also the induced emf polarity reverses due to the same reason.
(ii) The longer peak is due to increase in the rate of change of magnetic flux as the magnet comes out of the coil.

The figure shows an inductor L and a resistance R connected in parallel to a battery through a switch. The resistance R Which of the bulbs lights up earlier, when K is closed? Will the bulbs be equally bright after the same time?

1

(a)

(i) The bulb B₂ will light up earlier.
(ii) The bulb B₁ will grow more brightly

The axes of two magnets are collinear. One has poles of strength 80 Am separated by 125 mm, and the second has a magnetic moment of 12 A-m² with poles of strength 160 Am. Find the attractive force between the magnets if the north pole of one is 45 mm from the south pole of the second

1

(a)

Resultant force F = 2 attractive forces + 2 repulsive forces = 520 mN (attractive)

A stream of electron travelling with a speed at right angle to a uniform electric field E, is deflected in a circular path of radius “r” . Prove that e/m = v2 /rE.

1

(a)

Ee = Mv² /r

Neon -23 decays in the following way
²³Ne₁₀---------------\(\rightarrow\)²³Na₁₁ + ⁰e_-1+y
Find the minimum and maximum kinetic energy that the \(\beta\)-particle can have. The atomic masses of ²³Ne₁₀ and ²³Na₁₁ are 22.99454 and 22.98984 respectively. 

1

(a)

Mass defect ∆m= (22.9945-22.9898) =0.00474
Energy Q= (0.00474) (931.5)
=4.4MeV
Hence the energy of beta particle can range from 0 to 4.4MeV

which have greater ionizing power:α-particles or \(\beta\)-particles?

1

(a)

\(\alpha\) - particles have more ionizing power than \(\beta\) - particles  

Can a single nucleus emit \(\alpha\) – particle, \(\beta\) – particle and a γ – rays together?

1

(a)

No a nucleus either emits a \(\alpha\) – particle or a \(\beta\) – particle and if left in the exited state, it may emit \(\gamma \) – ray also.

Which gate is represented by the following diagram?

1

(a)

NAND GATE

what is heterodyning?

1

(a)

Mixing two frequencies across nonlinear impedance

what should be the length of the dipole antenna for a carrier wave of 5 x 10⁸ hz ?

1

(a)

L =c/2 ν.

A microwave telephone link operating at the cenral frequency of 10 GHz has been established .If 2 % of this is available for microwave communication channel, then how many telephones channels can be simultaneously granted if each telephone is allotted a band width of 8 KHz

1

(a)

Microwave communication channel width = \(\frac { 2 }{ 100 } \times 10GHz\)
= 0.2 Ghz
band width of channel = 8 KHz
= 2.5 x 10⁴