Physics Test 10...

From the point of view of significant figures which of the following statement is correct ?

(i) 10.2 cm + 8 cm = 18.2 cm            (ii) 2.53 m – 1.2 m = 1.33 m        

(iii) 4.2 m × 1.4 m = 5.88 m²            (iv) 3.6 m / 1.75 sec = 2.1 m/sec

The mass per unit length of a rod (length 2 m) varies as ρ = 3x kg/m. The moment of inertia (in kg m²) of the rod about a perpendicular axis passing through the tip of the rod (at x = 0) is 

A steel rod of length 5 m is fixed between two rigid supports. The coefficient of linear expansion of steel is 12.5 × 10^–6/°C. The stress in the rod for an increase in temperature of 40°C is x × 10⁸N/m². (Young’s modulus for steel is 2 × 10¹¹ N/m²). The value of x is

In a meter bridge circuit as shown, when one more resistance of 100 Ω is connected is parallel with  unknown resistance x, then ratio ℓ₁/ℓ₂ become 2. If ℓ₁ is balance length of the uniform wire AB, then the value of x must be :

A small loop of wire of area A = 0.01 m², N = 40 turns and resistance R = 20Ω is initially kept in a uniform magnetic field B in such a way that the field is normal to the plane of the loop. When it is pulled out of the magnetic field, a total charge of Q = 2 × 10^–5 C flows through the coil. The magnitude of the field B is

An LR circuit with a battery is connected at t = 0. Which of the following quantity is not zero just after the connection ?

A hollow, conducting spherical shell of inner radius R₁ and outer radius R₂ encloses a charge q inside, which is located at a distance d (< R₁) from the centre of the spheres. The potential at the centre of the shell is 

The atomic number of element which has a k_α x-rays line of wavelength 1.8 Å is 20 + n, the value of n is : (R = 1.1 × 10⁷)

A collimated beam of light of diameter 1 mm is propagating along the x-axis. The beam is to be expanded to a collimated beam of diameter 10 mm using a combination of two convex lenses. A lens of focal length of 50 mm and another lens with focal length F are to be kept at a distance d between them. The value of F and d respectively, are 

Half life of a radioactive substance A is two times the half life of another radioactive substance B. Initially the number of nuclei of A and B are N_A and N_B respectively. After three half lives of A number of nuclei of both are equal. Then the ratio N_A/N_B is