$A$ coil of $50$ turns and $4$ cm radius carries $2$ $A$ current. The magnetic field at its centre is ...... mT.

If the difference between the roots of the equations ${x^2} + ax + b = 0$ and ${x^2} + bx + a = 0$ is the same,and $a \ne b$,then:

The bacteria increases at a rate proportional to the number of bacteria present. If the original number $N$ doubles in $4 \text{ hours}$,then the number of bacteria in $12 \text{ hours}$ will be (in $N$)

The product$(s)$ formed when $H_2O_2$ reacts with disodium hydrogen phosphate is

Assertion $(A)$: Rapidly changing temperatures can be measured by thermocouples. Reason $(R)$: The thermal capacity of the junction of a thermocouple is very small.

$A$ metallic wire with tension $T$ and at temperature $30^{\circ} C$ vibrates with its fundamental frequency of $1 \ kHz$. The same wire with the same tension but at $10^{\circ} C$ temperature vibrates with a fundamental frequency of $1.001 \ kHz$. The coefficient of linear expansion of the wire is