Question

(d) optional for g2 science
emily replaces four of the light bulbs in her house with led light bulbs. she keeps the led light bulbs switched on for 10 hours a day.
(i) calculate the amount of electrical energy consumed by an led light bulb in kwh, for one day.
amount of electrical energy consumed =
(ii) calculate the amount of electrical energy consumed by an led light bulb in
for one day.
amount of electrical energy consumed =
(iii) the electricity tariff is 15 cents per kwh.
calculate the monthly cost of electrical energy consumption of all four led light bulbs. assume that there are 30 days in a month. leave your answer in dollars.

Explanation:

Step1: Identify Missing Data

The problem involves calculating electrical energy consumption, but the power rating (in watts or kilowatts) of the LED light bulb is not provided. Let's assume a typical LED bulb power, say \( P = 0.01 \, \text{kW} \) (10 watts) for illustration.

Step2: Recall Energy Formula

The formula for electrical energy is \( E = P \times t \), where \( E \) is energy in kWh, \( P \) is power in kW, and \( t \) is time in hours.

(I) Energy for One Bulb in a Day

Step1: Define Variables

\( P = 0.01 \, \text{kW} \), \( t = 10 \, \text{hours} \)

Step2: Apply Formula

\( E = 0.01 \times 10 = 0.1 \, \text{kWh} \)

(II) Energy for Four Bulbs in a Day

Step1: Multiply by Number of Bulbs

Number of bulbs \( n = 4 \)
\( E_{\text{total}} = 4 \times 0.1 = 0.4 \, \text{kWh} \)

(III) Monthly Cost

Step1: Daily Energy for Four Bulbs

From (II), \( E_{\text{daily}} = 0.4 \, \text{kWh} \)

Step2: Monthly Energy

\( E_{\text{monthly}} = 0.4 \times 30 = 12 \, \text{kWh} \)

Step3: Calculate Cost

Tariff \( = 15 \, \text{cents/kWh} = 0.15 \, \text{dollars/kWh} \)
Cost \( = 12 \times 0.15 = 1.8 \, \text{dollars} \)

(Note: If the actual power rating is different, substitute \( P \) in the above steps.)

Answer:

(I) If \( P = 0.01 \, \text{kW} \), energy is \( \boldsymbol{0.1 \, \text{kWh}} \)

(II) If \( P = 0.01 \, \text{kW} \), energy is \( \boldsymbol{0.4 \, \text{kWh}} \)

(III) If \( P = 0.01 \, \text{kW} \), monthly cost is \( \boldsymbol{\$1.80} \)

(Actual values depend on the bulb's power rating, which was not provided in the problem.)