Identify the correct statement about the electric charges \( q_1 \) and \( q_2 \) from the figure given below.

Which one of the following can not be polarized?

A charge of \( 5 \mu C \) moves with a speed of \( 2 \times 10^6 \text{ m/s} \) along the positive \( y \)-axis. A magnetic field \( \vec{B} \) of strength \( (2\hat{i} + \hat{k})\text{T} \) exists in space. The magnetic force acting on the charge is :

The average emf induced in a coil is 2 V when current is changed in 0.4 s.
(A) from 5 A to 2 A and the self-inductance of the coil is 0.266 mH
(B) from 4 A to 4 A in the opposite direction, the self-inductance of the coil is 0.10 mH

The following have zero average value in a plane electromagnetic wave

A Convex lens having a power of one dioptre is made of glass having refractive index 1.48. What will be the power of convex lens made of material with refractive index 1.6 and same dimension

A cell of constant emf is first connected to a resistance \( R_1 \) and then connected to a resistance \( R_2 \). If power delivered in both cases is same, then the internal resistance of the cell is

Read the following passage carefully and answer the given questions.
Biofertilisers
Biofertilisers are organisms that enrich the nutrient quality of the soil and their main sources are bacteria, fungi and cyanobacteria. You have studied about the nodules on the roots of leguminous plants formed by the symbiotic association of Rhizobium. These bacteria can fix atmospheric nitrogen into organic forms. Other bacteria can also fix atmospheric nitrogen while free-living in the soil (examples Azospirillum and Azotobacter). Fungi are also known to form symbiotic associations with plants (mycorrhiza). Many members of the genus Glomus form mycorrhiza. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development. Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter in to the soil and increase its fertility. Currently, in our country, a number of biofertilisers are available commercially in the market and farmers use these regularly in their fields to replenish soil nutrients and to reduce dependence on chemical fertilisers.
In organic farming, there is -

A radioactive isotope has half-life of ' \(K\) ' years. How long will it take, so that activity reduces to \(6 . 2 5 \%\) of its original value?

The rate of change of area of a circle with respect to its circumference when radius is 6 cm, is

In what ratio should a shopkeeper mix two types of rice, one costing ₹ \(20\) per kg and another costing ₹ \(40\) per kg to get a rice variety costing ₹ \(28\) per kg ?

A small standing crop of phytoplankton supports a large standing crop of zooplankton. This can be correctly represented by:

The relative motion between the magnet and a coil is responsible for generation (induction) of electric current in the coil. This is in accordance with