Lightbulb A is marked \"10.0 W 120 V,\" and lightbulb B is marked \"25.0 W 120 V

Question

Lightbulb A is marked "10.0 W 120 V," and lightbulb B is marked "25.0 W 120 V." These labels mean that each lightbulb has its respective power delivered to it when it is connected to a constant 120-V source.

(a) Find the resistance of each lightbulb.

(b) During what time interval do 1.60 C pass into lightbulb A?
s

(d) In what time interval do 1.70 J pass into lightbulb A?
s

(f) Find the cost of running lightbulb A continuously for 30.0 days, assuming the electric company sells its product at $0.110 per kWh.
$

Explanation / Answer

a) resistance of bulb A RA=V2/P

here V=120v,P=10W then RA=1202/10=1440ohm

resistance of bulb A RB=V2/P

here V=120v,P=25W then RB=1202/25=576 ohm

b) time interval do 1.60 C pass into lightbulb A i=q/t and i=P/V then q/t=P/V

here q=1.6c,P=10W,V=120v ,t=?

1.6/t=10/120, t=19.2s

d) time interval do 1.70 j pass into light bulb A t=energy u/power p

here u=1.7j,p=10w then t=1.7/10=0.17s

f)consumption of current in 30 days=no of bulbs*wattage*time in hours=1*10*30*24=7200W=7.2kwh

per 1kwh 0.110$ then 7.2kwh electric bill is 7.2*0.11$=0.792$

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