{"id":343907,"date":"2023-01-06T13:40:50","date_gmt":"2023-01-06T08:10:50","guid":{"rendered":"https:\/\/infinitylearn.com\/surge\/question\/an-electric-refrigerator-rated-400-w-operates-for-8-hours-per-day-what-is-the-cost-of-the-energy-to-operate-it-for-30-days-at-rs-3-00-per-kwh\/"},"modified":"2025-06-26T18:03:24","modified_gmt":"2025-06-26T12:33:24","slug":"an-electric-refrigerator-rated-400-w-operates-for-8-hours-per-day-what-is-the-cost-of-the-energy-to-operate-it-for-30-days-at-rs-3-00-per-kwh","status":"publish","type":"questions","link":"https:\/\/infinitylearn.com\/surge\/question\/physics\/an-electric-refrigerator-rated-400w-operates-for-8hours-pe\/","title":{"rendered":"An electric refrigerator rated 400\u00a0W operates for 8\u00a0hours per day. What is the cost of the energy to operate it for 30\u00a0days at Rs.3.00\u00a0per kWh?"},"content":{"rendered":"","protected":false},"author":1,"template":"","meta":{"_yoast_wpseo_focuskw":"","_yoast_wpseo_title":"","_yoast_wpseo_metadesc":"An electric refrigerator rated 400\u00a0W operates for 8\u00a0hours per day. What is the cost of the energy to operate it for 30\u00a0days at Rs.3.00\u00a0per kWh?","custom_permalink":"question\/physics\/an-electric-refrigerator-rated-400w-operates-for-8hours-pe\/"},"categories":[],"acf":{"question":"

An electric refrigerator rated <\/span>400<\/mn> W<\/mi><\/math> operates for <\/span>8<\/mn> <\/mi>hours<\/mi><\/math> per day. What is the cost of the energy to operate it for <\/span>30<\/mn> days<\/mi><\/math> at <\/span>Rs<\/mi>.<\/mo>3<\/mn>.<\/mo>00<\/mn> per kWh<\/mi><\/math>? <\/span><\/p>

<\/p>

<\/p><\/spanstyle=\"font-family:'timesnewroman';-aw-import:ignore\"><\/pstyle=\"margin-top:0pt;margin-bottom:8pt;line-height:107%;font-size:12pt\"><\/spanstyle=\"font-family:'timesnewroman';-aw-import:ignore\"><\/pstyle=\"margin-top:0pt;margin-bottom:8pt;line-height:107%;font-size:12pt\">","options":[{"option":"Rs. 960<\/span>","correct":false},{"option":"Rs. 110<\/span>","correct":false},{"option":"Rs. 90<\/span>","correct":false},{"option":"Rs. 288<\/span> <\/span>","correct":true}],"solution":"An electric refrigerator rated <\/span>400<\/mn> W<\/mi><\/math> operates for <\/span>8<\/mn> <\/mi>hours<\/mi><\/math> per day. The cost of the energy to operate it for <\/span>30<\/mn> days<\/mi><\/math> at <\/span>Rs<\/mi>.<\/mo>3<\/mn>.<\/mo>00<\/mn> per kWh<\/mi><\/math> will be <\/span>Rs<\/mi>.<\/mo> <\/mi>288<\/mn>.<\/mo><\/math>
It is given that the electric power of the refrigerator <\/span>=<\/mo> <\/mi>400<\/mn> Watt<\/mi><\/math>,<\/span>
The time for which it is used on a daily basis <\/span>=<\/mo> <\/mi>8<\/mn> <\/mi>hrs<\/mi><\/math>,<\/span>
The number of days for which it operates <\/span>=<\/mo> <\/mi>30<\/mn> days<\/mi><\/math>.<\/span>
Thus, from the formula of electric energy consumed,<\/span>
    <\/span>Energy <\/mi>=<\/mo> Power <\/mi>\u00d7<\/mo> time <\/mi>\u00d7<\/mo> days <\/mi><\/math>
\u21d2<\/mo>Energy<\/mi>=<\/mo> <\/mi>400<\/mn> <\/mi>\u00d7<\/mo> <\/mi>8<\/mn> <\/mi>\u00d7<\/mo> <\/mi>30<\/mn> <\/mi><\/math>
\u21d2<\/mo>Energy<\/mi>=<\/mo> <\/mi>96000<\/mn> Wh<\/mi><\/math>
Hence, the total energy consumed after <\/span>30<\/mn> days<\/mi><\/math> is <\/span>96<\/mn> kWh<\/mi><\/math>.<\/span>
It is given, cost <\/span>per kWh<\/mi><\/math> is <\/span>Rs<\/mi>.<\/mo>3<\/mn>.<\/mo>00<\/mn><\/math>,<\/span>
Therefore, the total cost after <\/span>30<\/mn> days<\/mi><\/math> will be <\/span>=<\/mo> <\/mi>96<\/mn> <\/mi>\u00d7<\/mo> <\/mi>3<\/mn><\/math>
                                                                          <\/span>=<\/mo> Rs<\/mi>.<\/mo>288<\/mn><\/math>
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