The ratio of magnetic fields due to a bar magnet at the two axial point P1 and P2 which are separated from each other by 10 cm is 25; 2 point P1 is situated at 10 cm from the centre of the magnet. The magnetic length  of the bar magnet is (point P1 and P2  are o2n the same side  of magnet and distance of P2 from the centre is greater than the distance of P1  from the centre of the magnet)

A) 5 cm

B) 10 cm

C) 15 cm

D) 20 cm


A pipe closed at one end has a length of 83 cm. The number of possible natural oscillations of air column whose frequencies lie below 1000 Hz are (take, the velocity of sound in air =332 m/s)

A) 3

B) 4

C) 5

D) 6


The energy of an electron having de-Broglie wavelength $\lambda$ is

(where, h= planck's constant, m= mass of electron)

A) $\frac{h}{2m\lambda}$

B) $\frac{h^{2}}{2m\lambda^{2}}$

C) $\frac{h^{2}}{2m^{2}\lambda^{2}}$

D) $\frac{h^{2}}{2m^{2}\lambda^{}}$


Let  $x=\left[\frac{a^{2}b^{2}}{c}\right]$ be the physical quantity  , if the percentage  error in the measurement of physical quantities a, b and c is 2,3 and 4 per cent respectively, then percentage error in the measurement of x is 

A) 7%

B) 14%

C) 21%

D) 28%


A conducting wire has length L1 and diameter d1. After stretching the same wire length becomes L2 and diameter d2 . The ratio  of resistances before and after stretching is 

A) $d_2^4:d_1^4$

B) $d_1^4:d_2^4$

C) $d_2^2:d_1^2$

D) $d_1^2:d_2^2$