Physics Test 62

Assume that the silicon diode in the circuit requires a minimum current of 1mA to be above the knee point 0.7V of its I−V characteristics. Also, assume that the voltage across the diodes is independent of the current above the knee point. If V_B=5V what should be the maximum value of R so that the voltage is above the knee point?

A particle moving along x -axis has acceleration ′f′ at time ′t′, given by where f0′ and T′ are constants. The particle at ' t′=0 has zero velocity. In the time interval between ' t′=0 and the instant when f′=0, the velocity (vx) of the particle is

A transmitting antenna of height 20m and a receiving antenna of height h are separated by a distance of 40km for satisfactory communication in line-of-sight mode. The value of h (given radius of Earth is 6400km) is

A car starting from rest is accelerated at a constant rate α until it attains a speed v. It is then retarded at a constant rate β until it comes to rest. The average speed of the car for its entire journey is

Calculate the energy released in the following reaction.

A particle is executing linear simple harmonic motion of amplitude ′A′. What fraction of the total energy is kinetic when the displacement is half the amplitude?

A sound absorber attenuates the sound level by 20dB. The intensity decreases by a factor of

Two spherical conductors B and C having equal radii and carrying equal charges, repel each other with force F when kept apart at some distance. A third spherical conductor having the same radius as that of B, but uncharged, is brought in contact with B, then with C and finally removed away from both. The new force of repulsion between B and C is

At t=0, an arrow is fired vertically upwards with a speed of 100ms⁻¹. A second arrow is fired vertically upwards with the same speed at t=5 s. Then,

The mass of a planet is (1/10)^th that of earth and its diameter is half that of earth, the acceleration due to gravity is