Physics

'Gulab Jamuns' (assumed to be spherical) are to be heated in an oven. They are available in two sizes, one twice bigger (in radius) than the other. Pizzas (assumed to be discs) are also to be heated in oven. They are also in two sizes, one twice big (in radius) than the other. All four are put together to be heated to oven temperature. Choose the correct option from the following:

(a) Both size gulab jamuns will get heated in the same time

(b) Smaller gulab jamuns are heated before bigger ones

(c) Smaller pizzas are heated before bigger ones

(d) Bigger pizzas are heated before smaller ones

The electric flux through the surface

(a) In Fig. (iv) is the largest
(b) In Fig. (iii) is the least
(c) In Fig. (ii) is same as Fig. (iii) but is smaller than Fig. (iv)
(d) Is the same for all the figures

Mark the correct options:

(a) A system X is in thermal equilibrium with Y but not with Z. System Y and Z may be in thermal equilibrium with each other

(b) A system X is in thermal equilibrium with Y but not with Z. Systems Y and Z are not in thermal equilibrium with each other

(c) A system X is neither in thermal equilibrium with Y nor with Z. The systems Y and Z must be in thermal equilibrium with each other

(d) A system X is neither in thermal equilibrium with Y nor with Z. The system Y and Z may be in thermal equilibrium with each other

A point positive charge is brought near an isolated conducting sphere. The electric field is best given by.

A sphere, a cube and a thin circular plate, all of same material and same mass are initially heated to same high temperature.

(a) Plate will cool fastest and cube the slowest

(b) Sphere will cool fastest and cube the slowest

(c) Plate will cool fastest and sphere the slowest

(d) Cube will cool fastest and plate the slowest.

In figure two positive charges q₂ and q₃ fixed along the y-axis, exert a net electric force in the +x-direction on a charge q₁, fixed along the x-axis. If a positive charge Q is added at (x, 0), the force on q₁

(a) Shall increase along the positive x-axis
(b) Shall decrease along the positive x-axis
(c) Shall point along the negative x-axis
(d) Shall increase but the direction changes because of the intersection of Q with q₂ and q₃

The radius of a metal sphere at room temperature T is R, and the coefficient of linear expansion of the metal is α. The sphere is heated a little by a temperature ?T so that its new temperature is T+ ?T. The increase in the volume of the sphere is approximately

(a) 2παR?T

(b) πR²α?T

(c) 4πR³?T/3

(d) 4παR³ $\mathit{\alpha }$ ?T

Figure shows the electric field lines around three point charges A, B and C.

(i) Which charges are positive?
(ii) Which charge has the largest magnitude? Why?
(iii) In which region or regions of the picture could the electric field be zero? Justify your answer.
(a) Near A (b) Near B
(c) Near C (d) Nowhere

Heat is associated with

(a) Kinetic energy of random motion of molecules

(b) Kinetic energy of orderly motion of molecules

(c) Total kinetic energy of random and orderly motion of molecules

(d) Kinetic energy of random motion in some cases and kinetic energy of orderly motion in other

As the temperature is increased, the time period of a pendulum

(a) Increases as its effective length increases even though its centre of mass still remains at the centre of the bob

(b) Decreases as its effective length increases even though its centre of mass still remains at the centre of the bob

(c) Increases as its effective length increases due to shifting of centre of mass below the centre of the bob

(d) Decreases as its effective length remains same but the centre of mass shifts above the centre of the bob