He's 76.2 W lightbulb uses 66.2 J of electrical energy every second. However, only 4.9 J of electrical energy is converted into light energy of each check and what is the efficiency of the lightbulb? Give your answer as a percentage to at least three decimal places

7.402%

Explanation:

Given that the total electrical energy used by the bulb in every second is 66.2 J.

The useful energy converted to light energy is 4.9 J.

As efficiancy (in %) = (Useful energy)/(Total energy) x 100

So, the efficiency of the bulb = (4.9/66.2)x100=7.402%

Hence, the efficiency of the bulb is 7.402%.

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