Which effect of electric current is used in electroplating?

$(a)$ State $Ohm's$ law. Express it mathematically.
$(b)$ Write symbols used in electric circuits to represent:
$(i)$ Variable resistance.
$(ii)$ Voltmeter.
$(c)$ An electric bulb is rated $220 \, V$ and $100 \, W$. When it is operated on $110 \, V$,what will be the power consumed?

Define one watt.

Who invented the simple battery?

$A$ heater is joined in parallel with a $60\, W$ bulb and connected to the mains. If the $60\, W$ bulb is replaced by a $100\, W$ bulb,will the rate of heat produced by the heater be more,less,or remain the same?

$A$ $100 \text{ W}$ electric bulb is lighted for $2 \text{ hours}$ daily,and four $40 \text{ W}$ bulbs are lighted for $4 \text{ hours}$ everyday. Calculate the energy consumed (in $\text{kWh}$) in $30 \text{ days}$.