The instantaneous current from a a.c source is I = 10sin 314t The frequency of the source would be

Why do light emitting diodes are preferred over conventional incandescent low power lamps?

A long straight wire is carrying a current of 20 A. An electron is moving with a speed of \( 10^7 \text{ m/s} \) parallel to the wire. The force experienced by the electron when it is 2 cm away from the wire is:

From the given statements:
A. All photons in white light have same energy and momentum
B. When intensity of light increases the number of photons incident per second per unit area increases.
C. Photons are deflected by negative terminal of battery
D. Photoelectric (saturation) current increases with increase in the frequency of radiation
Choose the correct answer from the options given below:

One student has to make an electromagnet using a coil of copper wire. He needs a ferromagnetic material to make its core. This core material should have

A generator develops an e.m.f of 150 V and has a terminal potential difference of 125 V, when the armature current is 50 A, the resistance of armature will be

Which quantity is increased in a step down transformer?

Read the following paragraph and answer the given questions.
Repeated amplification is achieved by the use of a thermostable DNA polymerase (isolated from a bacterium, Thermus aquaticus), which remain active during the high temperature induced denaturation of double stranded DNA. The separated DNA fragments can be visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation. The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. The convention for naming these enzymes is the first letter of the name comes from the genus and the second two letters come from the species of the prokaryotic cell from which they were isolated, e.g., EcoRI comes from Escherichia coli RY 13. In EcoRI, the letter 'R' is derived from the name of strain. Roman numbers following the names indicate the order in which the enzymes were isolated from that strain of bacteria. Stanley Cohen and Herbert Boyer accomplished this in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid which was responsible for conferring antibiotic resistance. Since the DNA is enclosed within the membranes, we have to break the cell open to release DNA, RNA, protein, polysaccharides etc. The RNA can be removed by treatment with ribonuclease whereas proteins can be removed by treatment with protease. Other molecules can be removed by appropriate treatments and purified DNA ultimately precipitates out after the addition of chilled ethanol.

Stanley Cohen and Herbert Boyer constructed the first recombinant DNA by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid of ____________ resistance. which was responsible for conferring antibiotic

An \( \alpha \) particle and a proton enters a region of uniform magnetic field B with same momentum at right angle to magnetic field. The ratio of the radii of the circular paths of \( \alpha \) particle to proton is:

For the reactions \(5 Br ^{-}(a q)+ BrO _3^{-}(a q)+6 H ^{+}(a q) \rightarrow 3 Br _2(a q)+3 H _2 O (l)\) The rate of the reaction is :

If a young man drives his vehicle \(25 km / hr\), he has to spend Rs. 2 per km on petrol.
If he drives it at faster speed of \(40 km / hr\), the petrol cost increases to Rs. 5 per km.
He has Rs. 100 to spend on petrol and travel within one hour. The maximum distance he travels is :

If \(\left|\begin{array}{cc}2 x & 2 \\ 4 & x\end{array}\right|=10\), then \(x\) is:

If \(\vec{a}\) and \(\vec{b}\) are two non-zero vectors such that \(\vec{a} \cdot \vec{b}=|\vec{a} \times \vec{b}|\), then angle between \(\vec{a}\) and \(\vec{b}\) is :