What are the advantages of the null-point method in a Wheatstone bridge? What additional measurements would be required to calculate $R_{\text {unknown }}$ by any other method?
The advantage of null point method in a Wheatstone bridge is that the resistance of galvanometer does not affect the balance point, there is no need to determine current in resistances and the internal resistance of a galvanometer.
It is easy and convenient method for observer.
The $R_{\text {unknown }}$ can be calculated applying Kirchhoff's rules to the circuit. We would need additional accurate measurement of all the currents in resistances and galvanometer and internal resistance of the galvanometer.
What is the advantage of using thick metallic strips to join wires in a potentiometer?
In potentiometer, the thick metallic strips are used as they have negligible resistance and need not to be counted in the length $l_1$ of the null point of potentiometer. It is for the convenience of experimenter as he measures only their lengths along the straight wires each of lengths 1 m.
This measurements is done with the help of centimetre scale or metre scale with accuracy.
For wiring in the home, one uses Cu wires or Al wires. What considerations are involved in this?
The Cu wires or Al wires are used for wiring in the home.
The main considerations are involved in this process are cost of metal, and good conductivity of metal.
Why are alloys used for making standard resistance coils?
Alloys have small value of temperature coefficient of resistance with less temperature sensitivity.
This keeps the resistance of the wire almost constant even in small temperature change. The alloy also has high resistivity and hence high resistance, because for given length and cross-section area of conductor. ($L$ and $A$ are constant)
$$R \propto \rho$$
Power $P$ is to be delivered to a device via transmission cables having resistance $R_c$. If $V$ is the voltage across $R$ and $I$ the current through it, find the power wasted and how can it be reduced.
The power consumption in transmission lines is given by $P=i^2 R_c$, where $R_c$ is the resistance of transmission lines. The power is given by
$$P=V I$$
The given power can be transmitted in two ways namely (i) at low voltage and high current or (ii) high voltage and low current. In power transmission at low voltage and high current more power is wasted as $P \propto i^2$ whereas power transmission at high voltage and low current facilitates the power transmission with minimal power wastage.
The power wastage can be reduced by transmitting power at high voltage.