The efficiency of the appliance is 0.62 (62%)
Explanation:
The relationship between the power of the appliance and the energy used by it is
[tex]P=\frac{E}{t}[/tex]
where
P is the power
E is the energy transferred in input
t is the time elapsed
For this appliance,
P = 7 W
So, in t = 42 s, the energy transferred in input is
[tex]E_{in}=Pt=(7)(42)=294 J[/tex]
We are told that the useful energy in output however is
[tex]E_{out}=183 J[/tex]
Therefore, the efficiency of the appliance is
[tex]\eta=\frac{E_{out}}{E_{in}}=\frac{183}{294}=0.62[/tex]
Learn more about power:
brainly.com/question/7956557
#LearnwithBrainly
