Current Electricity — Physics STD 12 Science — Question

If all the particle of a system lie in a cube, is it neccesary that the centre of mass be in the cube?

A particle executing simple harmonic motion comes to rest at the extreme positions. Is the resultant force on the particle zero at these positions according to Newton's first law?

Which radiations do not produce photo-electric effect in metals?

Write SI unit of magnetic flux. Is it a scalar or a vector quantity?

A point charge Q is placed at point ‘O’ as shown in the figure. Is the potential at point A, i.e. V_A, greater, smaller or equal to potential, V_B, at point B, when Q is (i) positive, and (ii) negative charge?

Four 2cm × 2cm × 2cm cubes of ice are taken out from a refrigerator and are put in 200ml of a drink at 10°C.

1. Find the temperature of the drink when thermal equilibrium is attained in it.
2. If the ice cubes do not melt completely, find the amount melted. Assume that no heat is lost to the outside of the drink and that the container has negligible heat capacity. Density of ice = 900kg-m^-3, density of the drink = 1000kg-m^-3, specific heat capacity of the drink = 4200Jkg^-1-K^-1, latent heat of fusion of ice = 3.4 × 10⁵J-kg^-1.

Write the ratio of the number of free electrons and holes in an intrinsic semiconductor.

Why a galvanometer is not used as an ammeter in the same form?

Answer the following questions:
The earth’s magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

V – I graph for a metallic wire at two different temperatures T₁ and T₂ is as shown in the figure. Which of the two temperatures is higher and why?