Physics Current Electricity Level: High School
Heating effect of current
One light bulb is marked “15 W 120 V” and another “60 W 120 V” . This means that each transforms this amount of electrical energy into light and heat per second when plugged into a constant 120-V potential difference . (You may assume 3 significant digits for the markings) .a) Find the resistance of each bulb . When they are connected to a 120 V power supply which bulb is brighter ?
b) How longs does it take for 1.00 C to pass through the dim bulb ? How is this charge different upon its exit versus its entry into the bulb ?
c) How long does it take the dim bulb to dissipate 1.00 J of energy ?
d) Find the cost of running the dim bulb continuously for 30.0 days if the electric company sells its product at $0.800 per kilowatt-hour (kWh) .
e) What physics quantity does the electric company sell ? What is the price for one SI unit of this quantity ?
f) Assume you can buy gasoline at $2.00 gallon and each gallon contains 114000 Btu . What is the ratio of the cost energy from the electrical power company over the cost of energy from the gas pump ?
