a). Since the bulbs are in series, their total resistance is the sum of their individual resistances. The total resistance in the series circuit is 6 ohms.
b). The current in the circuit is (voltage between the ends) / (total resistance) .
Current = 12 V / 6 ohms = 2 Amperes.
c). The power dissipated by any component can be expressed in different ways,
and if we're smart, we pick the formula that makes the problem easy for us.
-- Power = (voltage) x (current)
-- Power = (current)² x (resistance)
-- Power = (voltage)² / (resistance)
For this one, I think the middle formula is easiest.
Power = (current)² x (resistance) = (2 A)² x (3 ohms) = 12 watts for each bulb
d). Each bulb dissipates 12 watts,so for both bulbs, the battery has to supply 24 watts.
Check this solution with the first formula for power, above:
-- Power = (voltage) x (current)
Battery power = (battery voltage) x (current) = (12 V) x (2 A) = 24 watts Check. yay!
