1. agree Power = Voltage* current
so i = P/V = 4/120 = .0333 amps
2. R = V/i = V*2/P = 3600 ohms
3. Power * time = energy used
= 4 * 2 = 8 watt hours = .008 kwhr
.008*.12 = .00096 dollars
You have an LED bulb that uses 4 watts of power and gives an output of 170 lumens. The operating voltage is 120 volts. Using this data, find the following.
1. What is the current that the LED bulb uses?
Ans. 0.03 ampere
2. What is the effective resistance of this bulb?
I'm not sure what they mean by effective resistance, but I found the resistance to be 4000 ohms.
3. How much does it cost to use this bulb for 2 hours at a rate of $0.12/kWh?
Ans. $0.00144
1 answer