An oil drop of mass m carrying a charge +q is held stationary in air by an electric field E. The electric field is correctly given by

A straight wire of length 2 m and mass 50 g carrying a current of 4 A is balanced in air with the force due to uniform magnetic field acting perpendicular to the length of the wire. The magnitude of magnetic field is:

A bar magnet is cut into two equal halves along a plane parallel to the magnetic axis. The one parameter which remains unchanged is

An electron in a hydrogen atom emits wavelengths during the transitions given below. Arrange these wavelengths in ascending order.
(A) from n = 3 to n = 2
(B) from n = 2 to n = 1
(C) from n = \( \infty \) to n = 1
(D) from n = \( \infty \) to n = 3
(E) from n = 4 to n = 1
Choose the correct answer from the options given below:

Current sensitivity of a galvanometer increases if
A. total number of turns is increased in the coil.
B. area of the coil is decreased.
C. the magnetic field induction is decreased.
D. torsional constant is decreased.
Choose the correct answer from the options given below:

Two Polaroids are placed in such a way that their axes make an angle of 60° with each other. If an unpolarized light is incident on a system of these Polaroids, the fraction of transmitted light to the incident light will be

The mutual inductance of a pair of solenoids depends on

ELISA is based on the principles of:

The area (in sq. units) bounded by the parabola \(y^2=16 x\) and its latus rectum is

Match List-I with List-II

List-I (Optical instrument)	List-II (Magnifying power)
(A) Magnifying power m of a simple microscope	(I) \( m = 1 + (D/f) \)
(B) Magnifying power m of a simple microscope if the image is at infinity	(II) \( m = (L/f_0) \times (D/f_e) \)
(C) Magnifying power m of a compound microscope	(III) \( m = f_0 / f_e \)
(D) Magnifying power m of a telescope	(IV) \( m = D/f \)

Choose the correct answer from the options given below:

Choose the correct statements:
A. Diamagnetic substances have non zero resultant magnetic moment.
B. The magnetisation of a paramagnetic material is inversely proportional to the absolute temperature T.
C. At high enough temperature, a ferromagnet becomes a paramagnet.
D. Magnetic permeability of ferromagnets, \(u \gg 1\)
E. Susceptibility of Diamagnetic, \(X \gg 1\)

Read the passage carefully and answer the Questions
Carboxylic acids are the earliest organic compounds isolated from nature. These are also known as organic acids but are weaker acids as compared to mineral acids. However, they are more acidic than alcohols and phenols because of greater resonance stabilization of the parent acid and its conjugate base. The acidic strength is determined by the \(K _a\), which is called the acidity constant. The greater the value of \(K _a\), the greater the tendency of the acid to ionize and hence the stronger the acid. The acidic strength of the saturated aliphatic carboxylic acid depends upon the inductive effect and its position with respect to - COOH groups. Electron -donating substituents tend to decrease whereas electron-withdrawing substituents tend to increase the acidic strength. The acidic strength of the aromatic carboxylic acid, on the other hand depends upon both the inductive effect and the resonance effect of the substituents.
Which of the following groups when attached directly does not increase the acidity of the carboxylic acid?

The area (in sq. units) of the region bounded by the parabola \(y^2=8 x\) and the line \(x=2\) is