Power Estimations

Ways to represent Power:

Power is represented by Joules/second or in Watts.

Power=Force*Velocity

Power=IV=V^2/R=I^2(R)

Estimate the power required for typical objects:

Light:

• Assume LED bulb: 3.4 V, .02A
• P=IV, P=3.4V*.02A
• Power=.068 Watts

TV:

• assume power outlet 130 V
• Use LED with .02 Amps and 3.4 Volts
• Use proportionality: 3.4V/130V=.02A/xA
• Amps: .76A
• P=IV, Power=.76A(130V)--> 99.41 Watts

Computer:

• assume power outlet 130V
• Uses LED with .02 Amps and 3.4 Volts
• Use proportionality: 3.4V/130V=.02A/xA
• Amps: .76A
• P=IV, Power=.76A(130V)--> 99.41 Watts (same as TV)

Car:

• J=kg(m/s^2)
• Say car weighs 2000 kg and is traveling at 26m/s^2
• J=2000kg(26m/s^2)==50,000 Joules
• Assume it travels for 1 second→ 50,000 Watts

Motorcycle:

• J=kg(m/s^2)
• say motorcycle weighs 900kg and is traveling at 26m/s^2 for 1 second
• J=(900kg(26m/s^2))/1= 23400 Watts

Fridge:

• Fridge uses more power than a normal outlet probably around 300 V.
• use bulb inside of fridge to determine power?
• 3.4 V LED, .02 Amp
• use proportionality: 3.4V/300V=.02A/xA
• Amps=1.76A
• P=IV, Power=1.76A(300V) → 529.41 Watts

Oven:

• uses more power than normal outlet--around 300V
• uses bulb inside (count two bulbs for heating from bottom and top)
• (see proportionality used in fridge problem and multiply by 2):
• 1.76A*2= 3.52A
• P=IV, Power=3.52A(300V)=1056 Watts

Radio:

• battery operated radio running on 9V battery
• estimate is uses more amps than LED--about 10 amps
• 9V*10A=90 Watts