Question

1. your neighbour has an oven that uses 5000j of energy to produce 4000j of usable heat. your oven uses 7500j of energy to produce 6300j of heat ... which oven is more efficient?

Explanation:

Step1: Recall Efficiency Formula

Efficiency of an oven (a heat - producing device, here we can consider it in terms of energy conversion efficiency) is calculated by the formula: $\text{Efficiency} = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}}\times100\%$

Step2: Calculate Neighbor's Oven Efficiency

For the neighbor's oven, the useful energy output ($E_{out,neighbor}$) is $4000\space J$ and the total energy input ($E_{in,neighbor}$) is $5000\space J$.
Using the efficiency formula: $\text{Efficiency}_{neighbor}=\frac{4000}{5000}\times 100\% = 0.8\times100\% = 80\%$

Step3: Calculate Your Oven Efficiency

For your oven, the useful energy output ($E_{out,your}$) is $6300\space J$ and the total energy input ($E_{in,your}$) is $7500\space J$.
Using the efficiency formula: $\text{Efficiency}_{your}=\frac{6300}{7500}\times 100\%=\frac{6300\times100\%}{7500}=\frac{630000\%}{7500} = 84\%$

Step4: Compare the Efficiencies

We have $\text{Efficiency}_{neighbor} = 80\%$ and $\text{Efficiency}_{your}=84\%$.
Since $84\%> 80\%$, your oven is more efficient.

Answer:

Your oven is more efficient.