If the angle $2 \theta$ is acute,then the acute angle between the pair of straight lines $x^2(\cos \theta - \sin \theta) + 2xy \cos \theta + y^2(\cos \theta + \sin \theta) = 0$ is:

Which among the following is a pair of monocarboxylic acids?

In the circuit shown,the heat produced in $5 \Omega$ resistance due to current $I_2$ is $50 \text{ J/s}$. Then,the heat generated per second in $2 \Omega$ resistance is (in $\text{ J/s}$)

In the circuit shown,the reading of the Ammeter is doubled after the switch is closed. Each resistor has a resistance $1\,\Omega$ and the ideal cell has an $e.m.f.$ $10\,V$. Then,the Ammeter has a coil resistance equal to ............ $\Omega$

The protective coat of structural protein in viruses is made up of units called:

When a certain circuit consisting of a constant $e.m.f.$ $E$, an inductance $L$, and a resistance $R$ is closed, the current in it increases with time according to curve $1$. After one parameter $(E, L, \text{or } R)$ is changed, the increase in current follows curve $2$ when the circuit is closed a second time. Which parameter was changed and in what direction?