$(a)$ 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.

(N/A) $(i)$ Variable resistor or rheostat: It is used to change the resistance in a circuit,thereby controlling the current flowing through it.
$(ii)$ Wires crossing without joining: It represents two wires that cross each other without making any electrical contact.
$(b)$ The circuit diagram consists of a $12 \, V$ battery,a switch $(K)$,an ammeter $(A)$ in series with the combination,and a voltmeter $(V)$ connected in parallel across the three resistors ($5 \, \Omega$,$10 \, \Omega$,and $20 \, \Omega$) which are themselves connected in parallel.
$(c)$ Advantage of parallel connection: In a parallel circuit,if one electrical device stops working due to a defect or switch-off,the other devices continue to operate independently because each device has its own separate circuit path.