Class 12th

A copper wire of length 10m and radius $\left({10}^{-2}/\pi \right)\mathrm{m}$ has electrical resistance of $10\mathrm{\Omega }$ . The current density in the wire for an electric field strength of $10(\mathrm{V}/\mathrm{m})$  is:

Given below are two statements:

Statement I:
The boiling points of aldehydes and ketones are higher than hydrocarbons of comparable molecular masses because of weak molecular association in aldehydes and ketones due to dipole-dipole interactions.

Statement II:
The boiling points of aldehydes and ketones are lower than the alcohols of similar molecular masses due to the absence of H-bonding.

In the light of the above statements, choose the most appropriate answer from the options given below:

A light ray falls on a glass surface of refractive index $\sqrt[]{3}$ , at an angle ${60}^{?}$ . The angle between the refracted and reflected rays would be:

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): In a particular point defect, an ionic solid is electrically neutral, even if few of its cations are missing from it unit cells.
Reason (R): In an ionic solid, Frenkel defect arises due to dislocation of cation from its lattice site to interstitial site, maintaining overall electrical neutrality.

In the light of the above statements, choose the most appropriate answer from the options given below:

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): ICl is more reactive than I?.
Reason (R): I-Cl bond is weaker than I-I bond.

In the light of the above statements, choose the most appropriate answer from the options given below:

Let ${\mathrm{T}}_1$ and ${\mathrm{T}}_2$ be the energy of an electron in the first and second excited states of hydrogen atom, respectively. According the Bohr's model of an atom, the ratio ${\mathrm{T}}_1:{\mathrm{T}}_2$  is :

Given below are two statements:

Statement I: Photovoltaic devices can convert optical radiation into electricity.

Statement II: Zener diode is designed to operate under reverse bias in breakdown region.

In the light of the above statements, choose the most appropriate answer from the options given below:

A full wave rectifier circuit consists of two p-n junction diodes, a centre-tapped transformer, capacitor and a load resistance. Which of these components remove the ac ripple from the rectified output

Which of the following is suitable to synthesize chlorobenzene?

The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to $(1/16{)}^{\text{th}}$  of its initial value?