What is the lowest resistance that can be obtained by combining four coils of resistances $4\, \Omega, 8\, \Omega, 12\, \Omega$ and $24\, \Omega$?

If resistors are connected in series,the current through each resistor remains the same.

$(a)$ 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.

Out of the two wires $X$ and $Y$ shown below,which one has greater resistance? Justify your answer.

The voltage-current variation of two metallic wires $X$ and $Y$ at constant temperature are shown below. Assuming that the wires have the same length and the same diameter, explain which of the two wires will have larger resistivity.

Five bulbs are connected in a parallel circuit. If the second bulb blows out,what happens?