What happens to the resistance of a conductor when the length of the conductor is reduced to half?

In the given circuit,calculate $(i)$ total resistance of the circuit,and (ii) current shown by the ammeter.

Three $2\,\Omega$ resistors,$A$,$B$,and $C$,are connected as shown in the figure. Each of them dissipates energy and can withstand a maximum power of $18\,W$ without melting. Find the maximum current (in $A$) that can flow through the circuit such that none of the resistors melt.

How many microamperes $(\mu A)$ are equal to $1$ milliampere $(mA)$?

$(a)$ What do the following symbols represent in a circuit? Write the name and one function of each.
$(b)$ Draw a schematic diagram of a circuit consisting of a battery of $12 \, V$,three resistors of $5 \, \Omega$,$10 \, \Omega$,and $20 \, \Omega$ connected in parallel,an ammeter to measure the total current through the circuit,and a voltmeter to measure the potential difference across the combination of resistors.
$(c)$ State any one advantage of connecting electrical devices in parallel with the mains instead of connecting them in series in a household circuit.

Three resistors $R_{1}$,$R_{2}$,and $R_{3}$ are connected in parallel between points $A$ and $B$. The equivalent resistance $R$ is given by: