What appliances in our home work on 7A.) how to relate the ampere to watt conversion(eg:a bulb of 15 w need how many amp of current?

Power(Watts) = Volts * Amps

120 Vac and 240 VAC are common voltages and are usually country specific. A toaster in the US will operate on 120 V, but in many parts of Europe it may be 240 V.

viishnnumuckka: you multiply your voltage times your amperage you get your wattage. ( VOLTS X AMPS = WATTS ) or (WATTS divided by VOLTS = AMPS ) or ( WATTS divided by AMPS = VOLTS) so (7amps X 110volts = 770watt ) or (7amps X 240volts = 1680watts) (15watt light divided by 110volts = 1.36amps) hope this helps.

Actually 15/110 = .136 amps.
120 volts X 7 Amps = 840 Watts.
840 watts/15 Watts = 56 bulbs(7 amps)

How about just providing Ohm's Law and letting the poster do the math?