Which alloy is used to make the heating element (resistance wire) in an electric iron?

$(a)$ Define the term 'volt'.
$(b)$ State the relation between work,charge,and potential difference for an electric circuit. Calculate the potential difference between the two terminals of a battery,if $100 \ J$ of work is required to transfer $20 \ C$ of charge from one terminal of the battery to the other.

If the diameter of a conducting wire is doubled,how many times does its resistance become?

Find the equivalent resistance of the following circuit.

When three resistors of $5 \Omega$,$10 \Omega$,and $30 \Omega$ are connected in parallel in a circuit,what will be the equivalent resistance?

State with the help of a circuit diagram an activity to find the resistance $R$ of a given wire. $A$ current of $0.2 \, A$ passes through a resistor of $20 \, \Omega$. Find the potential difference across its ends.