We can reduce eddy currents in the core of transformer by :

Which of the following has zero average value in a plane electromagnetic wave?
(A) Electric field
(B) Magnetic field
(C) Electric energy
(D) Magnetic energy
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A non conducting solid sphere of radius R is uniformly charged. The magnitude of the electric field due to the sphere at a distance r from its center :
A. decreases as r increases, for 0 < r < \(\infty\)
B. increases as r increases, for r < R
C. becomes zero.
D. decreases as r increases, for R < r < \(\infty\)
Choose the correct answer from the options given below:

What is the approximate wavelength of the radiation emitted when the electron in an hydrogen atom jumps from n = \( \infty \) to n = 3?

A current of 10 A in primary of a circuit is reduced to zero at a uniform rate in \( 10^{-3} \text{ s.} \) If coeff. of mutual inductance is 3 H, the induced emf in the secondary would be :

Two nuclei have mass numbers in the ratio 1:8. The ratio of their nuclear radii would be :

Four capacitors are connected in the circuit as shown. The equivalent capacitance between P and Q will be :

The equivalent capacitance between P and Q will be :

Answer the question on the basis of passage given below:
Aldehydes are generally more reactive than ketones in nucleophilic addition reactions due to steric and electronic reasons. Sterically, the presence of two relatively large substituents in ketones hinders the approach of nucleophile to carbonyl carbon more than aldehydes having only one such substituent Electronically aldehydes are more reactive than ketones because two alkyl groups reduce the elctrophilicity of the carbonyl more effectively than in former.
For preparation of phenylethanoic acid from benzyl alcohol, reagents required are
A. HBr
B. \(CO _2\)
C. \(K C N\)
D. \(\Delta / H_3 O^{+}\)
E. \(AgNO _3\)
Choose the correct answer from the options given below:

An object of length 2.0 cm is placed at a distance of 1.5 f from a concave mirror where f is the magnitude of the focal length of the mirror. The length of the object is perpendicular to the principal axis. The length of the image will be

The impurity atoms with which pure silicon may be doped to make it a p-type semiconductor are those of
A. Phosphorous
B. Boron
C. Antimony
D. Aluminum
E. Graphite
Choose the correct answer from the options given below:

The speed of water current is half the speed of a motor boat.
The motor boat travels 15 km downstream in 1 hour.
Then the time taken to return to the starting point is:

It is currently 9:40 AM. What will be the time in next 610 hours?

A glass beaker contains water upto a height \( h_1 \) and kerosene oil above water upto height \( h_2 \). If the refractive index of water is \( \mu_w \) and that of oil is \( \mu_k \), then what will be the apparent shift in the position of the bottom of the beaker when viewed from above ?