What is electrical efficiency expressed as?

What is electrical efficiency expressed as?

• A. Eoutput / Einput x 100
• B. Einput / Eoutput x 100
• C. Eoutput - Einput
• D. Einput - Eoutput

Answer: (A)

Efficiency is the ratio of useful output energy to input energy, expressed as a percentage. So the correct expression is Eoutput divided by Einput, times 100. This shows how much of the electrical energy put in is actually delivered as useful energy. The other forms either invert the ratio or measure energy lost, not efficiency as a percentage. For example, if a device uses 100 J of input energy and provides 60 J as useful output, its efficiency is 60/100 × 100 = 60%.

Efficiency is the ratio of useful output energy to input energy, expressed as a percentage. So the correct expression is Eoutput divided by Einput, times 100. This shows how much of the electrical energy put in is actually delivered as useful energy. The other forms either invert the ratio or measure energy lost, not efficiency as a percentage. For example, if a device uses 100 J of input energy and provides 60 J as useful output, its efficiency is 60/100 × 100 = 60%.