The magnetic field on the axis of a circular loop of radius 100 cm carrying current $$I = \sqrt 2 \,A$$, at point 1 m away from the centre of the loop is given by :

Two rods one made of copper and other made of steel of same length and same cross sectional area are joined together. The thermal conductivity of copper and steel are 385 J s^$$-$$1 K^$$-$$1 m^$$-$$1 and 50 J s^$$-$$1 K^$$-$$1 m^$$-$$1 respectively. The free ends of copper and steel are held at 100$$^\circ$$C and 0$$^\circ$$C respectively. The temperature at the junction is, nearly :

The ratio of Coulomb's electrostatic force to the gravitational force between an electron and a proton separated by some distance is 2.4 $$\times$$ 10³⁹. The ratio of the proportionality constant, $$K = {1 \over {4\pi {\varepsilon _0}}}$$ to the gravitational constant G is nearly (Given that the charge of the proton and electron each = 1.6 $$\times$$ 10^$$-$$19 C, the mass of the electron = 9.11 $$\times$$ 10^$$-$$31 kg, the mass of the proton = 1.67 $$\times$$ 10^$$-$$27 kg) :

The position-time (x - t) graph for positive acceleration is