a 75 w compact fluorescent bulb operating at 30% efficiency. Calculate the amount of energy lost to heat and the amount of energy converted into light after the bulb has been on for 2.0h.
2*3600 seconds/h = 7200 seconds
75 * 7200 = 540,000 Joules total electricity use
.7 * 540,000 = heat Joules
.3 * 540,000 = light Joules
To calculate the amount of energy lost to heat and the amount of energy converted into light by a 75 W compact fluorescent bulb operating at 30% efficiency, we need to follow a few steps:
Step 1: Calculate the total energy consumed by the bulb.
The power (P) of the bulb is given as 75 W (watts). Energy (E) can be calculated using the formula:
E = P * t,
where t is the time in hours.
Plugging in the values:
E = 75 W * 2.0 h = 150 Wh (watt-hours).
Step 2: Calculate the energy converted into light.
Efficiency (η) is given as 30%. It represents the ratio of energy converted into useful work (light in this case) to the total energy consumed.
Efficiency = (Useful output energy / Total input energy) * 100%
Since we know the total input energy is 150 Wh, we can calculate the energy converted into light (E_light) using the formula:
E_light = (Efficiency / 100%) * Total input energy.
Plugging in the values:
E_light = (30% / 100%) * 150 Wh
E_light = 0.3 * 150 Wh = 45 Wh (watt-hours).
Step 3: Calculate the energy lost to heat.
The energy lost to heat (E_heat) can be calculated as the difference between the total input energy and the energy converted into light:
E_heat = Total input energy - Energy converted into light.
Plugging in the values:
E_heat = 150 Wh - 45 Wh = 105 Wh (watt-hours).
Therefore, after the bulb has been on for 2.0 hours, approximately 45 Wh (watt-hours) of energy is converted into light, and approximately 105 Wh (watt-hours) of energy is lost to heat.