What is a voltmeter? How is it connected in a circuit?

$(a)$ Why is the series arrangement not used for domestic circuits?
$(b)$ Why is tungsten used almost exclusively for the filament of electric lamps?
$(c)$ Why are the conductors of electric heating devices,such as bread toasters and electric irons,made of an alloy rather than a pure metal?
$(d)$ Why are copper and aluminium wires usually employed for electricity transmission?
$(e)$ Why does the cord of an electric heater not glow while the heating element does?

Resistance of a conductor increases with the increase in temperature.

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

Define one ampere.

The electric potential of a positively charged body is positive,and the electric potential of a negatively charged body is negative.