A student claims that adding oil increases the efficiency of a motor. The motor lifts loads before and after oil is added.
Which pair of measurements is sufficient to test the claim?
Total input energy and useful energy output, both before and after adding oil.
Useful energy output and final motor temperature, both before and after adding oil.
Total input energy and final motor temperature, both before and after adding oil.
Useful energy output and operating time, both before and after adding oil.