Portable radio receiver sets are generally not made with electron tube circuits. Why?

Why is it not possible to produce electro-megnetic waves in the visible region with modern electronic circuits in the laboratory ?

Why are mountain roads generally made winding upwards rather than going straight up?

An appratus was set up as shown in the figure. It was observed that when an aqueous solution of HCl was taken in the beaker and the circit was closed, the bulb in the circuit began to glow, but it did not glow when the experiment was repeated with glucose solution. what could be the reason? Would the bulb glow if the same experiment is repeated with an aqueous solution of NaOH? why?

An appratus was set up as shown in the figure. It was observed that when an aqueous solution of HCl was taken in the beaker and the circit was closed, the bulb in the circuit began to glow, but it did not glow when the experiment was repeated with glucose solution. what could be the reason? Would the bulb glow if the same experiment is repeated with an aqueous solution of NaCl? why?

In a household electric circuit, different appliances are connected in parallel to one another. Give two reasons An electrician puts a fuse of rating 5A in that part of domestic electrical circuit in which an electrical heater of rating 1.5 kW, 220V is operating. What is likely to happen in this case and why? What change, if any, needs to be made?

classically an electron can be in any orbit around nucleus of an atom. Then what determines the typical atomic size? Why is an atom not, say, thousand times bigger than its typical size? Thequestion had greatly puzzled Bohr before he arrived at his famous model of the atom that you have learnt in the text. To simulate what he might well have done before his discovery, let us play as followswith the basic constants of nature e, me, c and see if we can get a quantity with the dimensions of length that is roughly equal to the known size of an atom (~ 10 m).- You will find that the length obtained above is many orders of magnitude smaller than the atomic dimensions. Further, it involves c. But energies of atoms are mostly in non-relativistic domain where c is not expected to play any role. This is what may have suggested Bohr to discard c and look for else h had already made its appearance elsewhere. Bohr lay in recognising that h, m_e , and e will yield the right atomic size. Construct a quantity with the dimension of length from h, me, and e and confirm that its numerical value has indeed the correct order of magnitude.

Why is the orientation of the portable radio with respect to broadcasting station important?

Suppose that a radio tube insrted into a certain type of set has a probability0.2 of functioning more than 500 hours. If we test 4 tubes, what is the probability that exactly three of these function for more than 500 hours, .